gr-mcp-docs/reference/cospas-sarsat/g-series/g007.md

---
title: "G007: Handbook On Distress Alert Messages For Rescue Coordination Centres"
description: "Official Cospas-Sarsat G-series document G007"
sidebar:
  badge:
    text: "G"
    variant: "note"
# Extended Cospas-Sarsat metadata
documentId: "G007"
series: "G"
seriesName: "General"
documentType: "overview"
isLatest: true
issue: 3
revision: 3
documentDate: "October 2024"
originalTitle: "Handbook On Distress Alert Messages"
---

> **📋 Document Information**
>
> **Series:** G-Series (General)
> **Version:** Issue 3 - Revision 3
> **Date:** October 2024
> **Source:** [Cospas-Sarsat Official Documents](https://www.cospas-sarsat.int/en/documents-pro/system-documents)

---

___________________________________________________________________
HANDBOOK ON DISTRESS ALERT MESSAGES
FOR
RESCUE COORDINATION CENTRES (RCCs),
SEARCH AND RESCUE POINTS OF CONTACT (SPOCs)
AND
IMO SHIP SECURITY COMPETENT AUTHORITIES
C/S G.007
Issue 3 – Revision 3

___________________________________________________________________

![Image 1 from page 1](/images/cospas-sarsat/G-series/G007/G007_page_1_img_1.png)


HANDBOOK ON DISTRESS ALERT MESSAGES FOR
RESCUE COORDINATION CENTRES (RCCs),
SEARCH AND RESCUE POINTS OF CONTACT (SPOCs) AND
IMO SHIP SECURITY COMPETENT AUTHORITIES
HISTORY
Issue
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TABLE OF CONTENTS
Page
INTRODUCTION ...................................................................................................... 1–1
1.1
Overview ........................................................................................................... 1–1
1.2
Document Organisation .................................................................................... 1–1
1.3
Cospas-Sarsat .................................................................................................... 1–1
1.4
The Cospas-Sarsat System ................................................................................ 1–2
1.5
Reference Documents ....................................................................................... 1–6
COSPAS-SARSAT BEACONS ................................................................................. 2–1
2.1
Beacon Types .................................................................................................... 2–1
2.2
Characteristics of a 406-MHz Beacon .............................................................. 2–5
2.3
The Beacon Message ........................................................................................ 2–6
2.4
Hexadecimal Identity of a 406-MHz Beacon ................................................... 2–7
2.5
Direction Finding on 406-MHz Beacons .......................................................... 2–9
2.6
Return Link Service (RLS) ............................................................................... 2–9
2.7
GNSS Positions .............................................................................................. 2–10
2.8
Beacon Registration ........................................................................................ 2–11
2.9
International Beacon Registration Database (IBRD)...................................... 2–12
2.10
Beacon Regulation .......................................................................................... 2–14
2.11
Beacon Testing ............................................................................................... 2–14
2.12
Inadvertent Alert ............................................................................................. 2–15
COSPAS-SARSAT SATELLITE SYSTEMS........................................................... 3–1
3.1
MEOSAR .......................................................................................................... 3–1
3.2
LEOSAR ........................................................................................................... 3–6
3.3
GEOSAR ........................................................................................................ 3–12
MISSION CONTROL CENTRES ............................................................................ 4–1
4.1
General Principles ............................................................................................. 4–2
4.2
MCC Messages ................................................................................................. 4–4
4.3
Alerts with Invalid or Suspect Data ................................................................ 4–11
COSPAS-SARSAT DISTRESS MESSAGES ........................................................... 5–1
5.1
Paragraph 1: Message Type .............................................................................. 5–2
5.2
Paragraph 2: Current Message Number and MCC Beacon Reference ............. 5–3

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5.3
Paragraph 3: Beacon Message Information ...................................................... 5–3
5.4
Paragraph 4: Alert Position Information ........................................................... 5–8
5.5
Paragraph 5: Other Information ...................................................................... 5–12
5.6
Paragraph 6: Remarks ..................................................................................... 5–14
5.7
End of Message ............................................................................................... 5–15

EXAMPLES OF BEACON INCIDENTS
6-1
6.1
An Unlocated Detection to a Confirmed Update
6-1
6.2
From Unlocated Alert to Position Confirmation
6-7
6.3
A Position Confirmed Alert as the First Alert
6-13
6.4
A MEOSAR Alert Confirmed by a LEOSAR Alert
6-14
6.5
A Position Conflict Alert
6-16
6.6
A Notification of Country of Registration Alert
6-21
6.7
An Unresolved Doppler Position Match Alert
6-23
6.8
ELT(DT) Alerts
6-25
6.9
Cancellation Alerts
6-29
6.10
Sample SIT 985 Message with SGB Characteristics Based on TAC Number 6-30
6.11
A Ship Security Alert
6-31
6.12
An Alert with an Invalid Beacon Message
6-34
6.13
An Alert with a Satellite Manoeuvre Warning
6-34
6.14
An Interferer Alert
6-36

FREQUENTLY ASKED QUESTIONS
7-1
LIST OF ANNEXES
Page
Annex A: Acronyms and Terminology ................................................................................ A-1
Annex B: List of MID (Country) Codes .............................................................................. B-1
Annex C: Cospas-Sarsat Data Distribution Regions ........................................................... C-1
Annex D: How to Use the IBRD ......................................................................................... D-1


LIST OF FIGURES
Page
Figure 1.1: An Overview of the Cospas-Sarsat Beacon Detection System ........................... 1–3
Figure 1.2: A Sample SIT 185 Message ................................................................................ 1–6
Figure 2.1: Distress Beacon Types ......................................................................................... 2–1
Figure 2.2: The GISIS Maritime Security Website Interface................................................. 2–4
Figure 2.3: A Ship Security Alert System (SSAS) Beacon ................................................... 2–4
Figure 2.4: Beacon with Hex ID 3EF42AF43F81FE0 ........................................................... 2–8
Figure 2.5: Decode of Beacon 3EF42AF43F81FE0 .............................................................. 2–9
Figure 2.6: Information Graphic on Sources of False Alerts ............................................... 2–15
Figure 3.1: A Schematic View of the Galileo Constellation .................................................. 3–2
Figure 3.2: Footprint of a GPS MEOSAR Satellite ............................................................... 3–2
Figure 3.3: An Overview of the MEOSAR System ............................................................... 3–3
Figure 3.4: DOA Location Error Smaller than the Associated  Expected-Accuracy Value .. 3–4
Figure 3.5: Additional Expected-Accuracy-Related Boundary ............................................. 3–5
Figure 3.6: Probability of the Actual Beacon Location Being Within the Expected Accuracy-
Radius and Two-Times Expected Accuracy-Radius Circles .............................. 3–5
Figure 3.7: Four Passes of a LEOSAR Satellite .................................................................... 3–6
Figure 3.8: Footprint of LEOSAR Satellite (Sarsat-10) ......................................................... 3–7
Figure 3.9: Global coverage of a LEOSAR satellite .............................................................. 3–8
Figure 3.10: A Doppler Curve for a Hypothetical FGB ......................................................... 3–9
Figure 3.11: Two Doppler Locations from a LEOSAR Satellite Pass ................................. 3–10
Figure 3.12: Confirmation by Two LEOSAR Passes .......................................................... 3–11
Figure 3.13: Footprint of GEOSAR Satellite (MSG-2) ....................................................... 3–12
Figure 4.1: A Schematic View of the MCC Network ............................................................ 4–1
Figure 4.2: Two Doppler Locations from a LEOSAR Satellite Pass for an EPIRB .............. 4–5
Figure 4.3: Confirmation of LEOSAR Data by a MEOSAR Detection ................................ 4–6
Figure 4.4: Example of an Unresolved Doppler Match ....................................................... 4–10
Figure 5.1: A Sample SIT 185 Message ................................................................................ 5–1
Figure 6.1:  Sequence of Four SIT 185 Messages Sent to a SAR Service in Example 6-1 .... 6–1
Figure 6.2:  Sequence of Three Beacon Messages Sent in Example 6.2 ................................ 6–7


Figure 6.3:  Footprint of the GEOSAR INSAT-3A Satellite .................................................. 6–8
Figure 6.4:  LEOSAR Initial Alert ........................................................................................ 6–10
Figure 6.5:  Confirmation of Position Using a LEOSAR Alert ............................................ 6–12
Figure 6.6:  The Two SIT 185 Messages in Example 6.4 .................................................... 6–14
Figure 6.7:  ICAO 24-bit Addressing ................................................................................... 6–17
Figure 6.8:  GEOSAR GNSS Position Alert ........................................................................ 6–18
Figure 6.9:  LEOSAR Position Conflict Alert ...................................................................... 6–20
Figure 6.10 : Graphical Representation of the NOCR Alert Message ................................. 6–22
Figure 6.11: Unresolved Doppler Position Match ............................................................... 6–24
Figure 6.12: Ship Security Unlocated and Initial Alert ........................................................ 6–33
Figure 6.13: 406 MHz Interferer Alert ................................................................................. 6–37
Figure C.1: Western DDR Map ............................................................................................. C–1
Figure C.2: North West Pacific DDR Map ............................................................................ C–3
Figure C.3: South West Pacific DDR Map ............................................................................ C–4
Figure C.4: Central DDR Map ............................................................................................... C–5
Figure C.5: South Central DDR Map ..................................................................................... C–7
Figure C.6: Eastern DDR Map ............................................................................................... C–8
LIST OF TABLES
Page
Table 2.1: Maximum Precision of the FGB Location Protocols .......................................... 2–10
Table 2.2: Precision of the FGB Location Protocols with only Coarse Position ................. 2–11
Table 4.1: Determining if Two Locations for a Beacon are Independent .............................. 4–3
Table 5.1: Message Content for SIT 185 Messages ............................................................... 5–2
Table 5.2: GNSS Position Uncertainty ................................................................................ 5–13

1–1

INTRODUCTION
1.1
Overview
The purpose of this document is to provide Rescue Coordination Centre (RCC) personnel and
Search and Rescue Point of Contact (SPOC) personnel with an overview of the Cospas-Sarsat
System and an understanding of the Cospas-Sarsat distress alert messages and their contents.
This will allow RCCs and SPOCs to manage the response to search and rescue (SAR) incidents
involving Cospas-Sarsat distress alerts in an informed manner.
In the document, SAR Service will be used as a generic term to include both RCCs and SPOCs.
The document also provides an overview of Cospas-Sarsat Ship Security Alert System (SSAS)
alerts, which are similar to search and rescue distress alerts except that the notification of the
alert is sent to a Competent Authority rather than a SAR Service.
In the document, Responsible Agency will be used as a generic term to include SAR Services
and Competent Authorities.
1.2
Document Organisation
Section 1: provides a basic overview of the Cospas-Sarsat System.
Section 2: provides information on Cospas-Sarsat distress beacons.
Section 3: gives a brief overview of the satellite systems used by Cospas-Sarsat and the data
produced using those satellite systems.
Section 4: explains how a Mission Control Centre (MCC) processes beacon detection and
location data and how the data is sent to Responsible Agencies.
Section 5: provides detailed information on the types and contents of Cospas-Sarsat 406 MHz
distress alert messages.
Section 6: gives examples of 406 MHz distress alert messages sent to Responsible Agencies.
Section 7: lists some questions that are frequently asked by personnel of Responsible
Agencies and provides appropriate answers.
1.3
Cospas-Sarsat
The International Cospas-Sarsat Programme is a satellite-based search and rescue distress alert
detection system. The system was established in 1979 by Canada, France, the United States
and the former Soviet Union.
The name Cospas-Sarsat is formed from two acronyms. Cospas is an acronym for the Russian
words "Cosmicheskaya Sistema Poiska Avariynich Sudov" which translates to "Space System

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1–2

for the Search of Vessels in Distress". Sarsat is an acronym for Search and Rescue Satellite-
Aided Tracking.
The Mission Statement of the Programme states: “The International Cospas-Sarsat Programme
provides accurate, timely and reliable distress alert and location data to help search and rescue
authorities assist persons in distress.”
The objective of the Cospas-Sarsat System is to reduce, as far as possible, delays in the
provision of distress alerts to Responsible Agencies, and the time required to locate a distress
and to provide assistance. These delays have a direct impact on the probability of survival of
the person in distress at sea or on land.
To achieve this objective, Cospas-Sarsat participant governments and agencies implement,
maintain, co-ordinate and operate a satellite system capable of detecting distress alert
transmissions from distress beacons that comply with Cospas-Sarsat specifications and
performance standards, and of determining their position anywhere on the globe. The distress
alert and location data are provided by Cospas-Sarsat Participants to the relevant Responsible
Agencies.
Cospas-Sarsat co-operates with the International Civil Aviation Organization (ICAO), the
International Maritime Organization (IMO), the International Telecommunication Union
(ITU) and other international organisations to ensure the compatibility of the Cospas-Sarsat
distress alerting services with the needs, standards and applicable recommendations of the
international community.
Further information about the Programme can be found on the Cospas-Sarsat website
(www.cospas-sarsat.int).
A list of acronyms used in this document is provided in Annex A.
1.4
The Cospas-Sarsat System
The Cospas-Sarsat system consists of:
•
distress beacons that send transmissions on 406 MHz,
•
satellites that process and/or relay the signals transmitted by distress beacons,
•
a Ground Segment that consists of:
o
ground receiving stations called Local User Terminals (LUTs) which process the
satellite signals,
o
Mission Control Centres (MCCs) that provide the distress alert data to Responsible
Agencies. Each Responsible Agency is supported by an MCC that sends beacon
detection and location data (known as beacons alerts) to the Responsible Agency.
As the name suggests, the Responsible Agency is responsible for managing the
response to the beacon alerts,

1–3

o
Return Link Service Provider (RLSP) that provides the service offered by some
GNSS systems that sends a notification to the distress beacon after it has been
detected by the Cospas-Sarsat System. (see section 2.6).
Figure 1.1: An Overview of the Cospas-Sarsat Beacon Detection System
The steps in Figure 1.1 are explained in the following sections.
1.4.1
Step 1: Distress Beacons
There are four types of Cospas-Sarsat distress beacons:
1.
Emergency Locator Transmitters (ELTs), including ELTs for distress tracking
(ELT(DT)s), are designed for aviation use;
2.
Emergency Position-Indicating Radio Beacons (EPIRBs) are designed for
maritime use;
3.
Personal Locator Beacons (PLBs) are intended for use by an individual person
(i.e., not necessarily linked to an aircraft or a ship); and
4.
Ship Security Alerting System (SSAS) beacons are designed for security situations
for SOLAS vessels. Unlike the other types of beacons that have alert messages
sent to a SAR Service, all SSAS alerts are sent to the Competent Authority for the
country of registration of the SSAS beacon.
Each type of distress beacon has different characteristics (such as duration of continuous
operation (battery life) and beacon activation method) but all work in the same manner
- by transmitting an emergency message on 406 MHz. A unique hexadecimal identifier

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1–4

(known as the Hex ID of the beacon) can be extracted from the emergency message. The
Hex ID includes the country of registration for the beacon.
A distress beacon may contain an internal receiver capable of determining a Global
Navigation Satellite System (GNSS) location or may be capable of receiving data from
an external device able to supply a GNSS location. The GNSS systems includes the
American Global Positioning System (GPS), the European Galileo system, the Russian
Glonass system and the BDS of China (P. R. of). The GNSS location may be transmitted
as part of the emergency message and is also known as an encoded location.
1.4.2
Step 2: Search & Rescue Satellites
The Cospas-Sarsat System uses three different satellite systems to detect distress
beacons. The three satellite systems have different characteristics, but all provide beacon
detection and location data:
1.
The MEOSAR (Medium-altitude Earth Orbit Search and Rescue) satellites are the
most recent addition to the Cospas-Sarsat System. MEOSAR satellites orbit the
Earth at altitudes between 19,000 and 24,000 kilometres.
2.
The LEOSAR (Low-altitude Earth Orbit Search and Rescue) satellites were the
original satellites used in the Cospas-Sarsat system. LEOSAR satellites orbit the
Earth in near-polar orbits at altitudes between 700 and 1,000 kilometres.
3.
The GEOSAR (Geostationary Earth Orbit Search and Rescue) satellites appear
stationary from the Earth. The GEOSAR satellites are in orbit approximately
36,000 kilometres from the Earth.
1.4.3
Step 3: Local User Terminals
Each satellite system has its own type of LUT (Local User Terminal) that tracks the
satellites and processes the signals received from the satellites.
The MEOSAR system has ground stations called MEOLUTs; each MEOLUT tracks
multiple MEOSAR satellites simultaneously. Using Difference of Arrival (DOA)
techniques (described in section 3.1), a MEOLUT that receives data that has been
relayed from a beacon through three or more satellites can compute a location estimate
for that beacon.
The LEOSAR system has LEOLUTs. Each LEOLUT has a single antenna that tracks a
LEOSAR satellite when in view. The LEOLUT collects data from the satellite. A
LEOLUT uses Doppler techniques (described in section 3.2) to generate location data.
The GEOSAR system has GEOLUTs. Each GEOLUT receives data from one satellite
(as the GEOSAR satellite is always in view) and collects and processes the data from
that satellite. A GEOLUT is unable to generate a location for a beacon unless the beacon
transmits a GNSS position.
Each LUT forwards detection and location data to its associated Mission Control Centre.

1–5

1.4.4
Step 4: Mission Control Centres
The Mission Control Centres (MCCs) form a network that distributes the beacon
detection data around the world. Each MCC receives data from its LUTs and also data
from the network of MCCs. The MCC processes data for each beacon incident, using
the unique Hex ID of the beacon to identify all the detections associated with the same
beacon incident.
For each incident alert received the MCC determines the responsible MCC for the
distribution of that alert. If it is itself the responsible MCC, it determines the Responsible
Agency or Agencies to be informed of the beacon activation and sends the data to the
Responsible Agency directly. Otherwise, the MCC sends the data through the MCC
network to the responsible MCC that can deliver it to the relevant Responsible Agency.
1.4.5
Step 5: Responsible Agencies
A Responsible Agency is either an RCC or SPOC (for ELT, EPIRB and PLB
activations), or a Competent Authority (for SSAS activations). The Responsible Agency
receives beacon alerts from its associated MCC. Each beacon alert contains beacon
detection data for the related beacon incident and may also have location data. The
messages sent between an MCC, and its national Responsible Agencies are a matter of
national sovereignty and are not explicitly defined by Cospas-Sarsat. The message
formats described in this document are specified by Cospas-Sarsat for communications
between an MCC and a foreign Responsible Agency. However, most MCCs use the
same format (or something very similar to it) to communicate with their national
Responsible Agencies.
The information that is distributed by an MCC is structured in a format known as Subject
Indicator Type (SIT) format. In particular, the information that is sent from an MCC to
a Responsible Agency is usually a plain text message in a format known as a SIT 185
format. An example of a SIT 185 message is shown in Figure 1.2. The fields of the
SIT 185 message are explained in detail in sections 5 and 6.
ELT(DT) data is only transmitted to the Location of Aircraft in Distress Repository
(LADR) by the nodal MCC associated with the destination MCC (or by another nodal
MCC on its behalf), in a special message format. This message format is not explained
further in this Handbook.

1–6

1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 12590  AUMCC REF C00F429578002C1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER – PLB
SERIAL NO 0042334
HEX ID C00F429578002C1
COUNTRY OF BEACON REGISTRATION 512/NEWZEALAND
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 08 JAN 17 0354 UTC BY SARSAT 10
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A - 41 14 S  172 31 E  PROB 79 PERCENT
DOPPLER B - 48 20 S  135 51 E  PROB 21 PERCENT
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0280 MHZ
6.  REMARKS NIL
END OF MESSAGE
Figure 1.2: A Sample SIT 185 Message
1.5
Reference Documents
The Cospas-Sarsat documents listed below are available free-of-charge from the Cospas-
Sarsat web site at www.cospas-sarsat.int:
•
C/S A.001 – Cospas-Sarsat Data Distribution Plan (DDP)
This document provides requirements for the exchange of alert and System data between
MCCs and Responsible Agencies.
•
C/S A.002 – Cospas-Sarsat Mission Control Centre Standard Interface Description
(SID)
This document provides information on message content and formats for the automatic
exchange of data between MCCs and to Responsible Agencies. It also describes the
message content and format used by MCCs to send data for ELT(DT)s to the LADR.
•
C/S A.005 – Cospas-Sarsat Mission Control Centre Performance Specification and
Design Guidelines
This document provides the specific performance requirements for a Cospas-Sarsat
Mission Control Centre (MCC).

1–7

•
C/S G.003 – Introduction to the Cospas-Sarsat System.
This document provides detailed information of the System history, Programme
Management, concept of operation and a description of the various components. It is the
ideal document to read to obtain a general understanding of the Cospas-Sarsat System.
•
C/S G.005 – Cospas-Sarsat Guidelines on 406 MHz Beacon Coding, Registration and
Type Approval.
This document was developed as an aide to help in understanding the beacon coding and
the processes of registration and type approval. It also complements and assists in the
understanding of some of the more complex details in the beacon technical specification
document, C/S T.001.
•
C/S G.010 – MCC Handbook.
This document describes responsibilities and functions of an MCC and MCC operators.
•
C/S P.011 – Cospas-Sarsat Programme Management Policy.
This high-level document provides information on all aspects of the System and its
management. In the main, it is intended for senior Managers.
•
C/S S.007 – Handbook of Beacon Regulations
This document provides a summary of regulations issued by Cospas-Sarsat Participants
and other countries regarding the carriage of 406 MHz beacons, and includes
information on the coding and registration of 406 MHz beacons in each country.
•
C/S T.001 – Specifications for Cospas-Sarsat 406 MHz Distress Beacons
This document defines the specifications for the development and manufacture of
406 MHz distress First-Generation Beacons (FGBs) and the beacon message content.
•
C/S T.018 – Specifications for Second-Generation Cospas-Sarsat 406 MHz Distress
Beacons
This document defines the specifications for the development and manufacture of
406 MHz distress Second-Generation Beacons (SGBs) and the beacon message content.
Other materials, such as sets of videos, graphics, images, history book, Information Bulletin
and published articles are available free-of-charge from the Cospas-Sarsat website at
www.cospas-sarsat.int under the Media Gallery tab.
Documents listed below are available from the International Maritime Organization
(www.imo.org) or the International Civil Aviation Organization (www.icao.int) for a fee:
•
Doc 9731 – AN/958 – IAMSAR Manual (International Aeronautical and Maritime
Search and Rescue Manual),
•
Doc 8585 – “Designators for Aircraft Operating Agencies, Aeronautical Authorities and
Services”,
•
Doc 10054 – “Manual on Location of Aircraft in Distress and Flight Recorder Data
Recovery”,

1–8

•
[Doc 10165 – “Manual on Global Aeronautical Distress and Safety System (GADSS)”].
- END OF SECTION 1 -

2–1

COSPAS-SARSAT BEACONS
2.1
Beacon Types
The Cospas-Sarsat System provides alerting services for the following four types of beacons:
1.
Emergency Locator Transmitters (ELTs), including ELT(DT)s, are designed for aviation
use;
2.
Emergency Position-Indicating Radio Beacons (EPIRBs) are designed for maritime use;
3.
Personal Locator Beacons (PLBs) are intended for use by an individual person (i.e., not
necessarily linked to an aircraft or a ship); and
4.
Ship Security Alerting System (SSAS) beacons are designed for security situations for
SOLAS vessels.
Figure 2.1: Distress Beacon Types

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2–2

2.1.1
ELTs
ELTs are designed for use in aircraft.
Most ELTs are installed in aircraft so that they activate on impact. An automatic
activation is triggered by strong acceleration or deceleration on a “G” sensor device.
These ELTs can also be activated manually by the crew in the cockpit.
A distress tracking ELT, or ELT(DT), may be activated by the aircraft avionics system
when it detects an unusual in-flight situation, as defined by ICAO in Global Aeronautical
Distress and Safety System (GADSS) documents, that indicates that the aircraft is in
imminent danger of crashing. These ELTs can also be activated manually by the crew
in the cockpit. An ELT(DT) can only be deactivated by the same means used for
activation (i.e., by avionics or manually).
Other ELT models than ELT(DT) that are carried on an aircraft may have to be activated
manually.
Except for ELT(DT)s, all ELTs are required to have a minimum duration of continuous
operation (battery life) of 24 hours. ELT(DT)s are required to have a minimum duration
of continuous operation (battery life) of 370 minutes and may be powered by the aircraft.
2.1.2
EPIRBs
EPIRBs are designed for maritime use and float in water. An EPIRB is required to have
positive buoyancy in water to ensure that the antenna is vertically upright, providing the
best antenna performance for beacon transmission.
There are two activation mechanisms for EPIRBs. EPIRBs can have an automatic
activation switch that incorporates a water sensor. When the sensor comes in contact
with water for a few seconds, the EPIRB will self-activate. EPIRBs with an automatic
activation switch can also be manually activated.
Other EPIRB models can only be manually activated.
A float-free EPIRB is housed in an enclosure that deploys (using a pressure-sensitive
hydrostatic release unit) the EPIRB when the enclosure is submerged. The float-free
EPIRB has an automatic activation switch that activates when it comes in contact with
water.
A non-float-free EPIRB is either loose in the vessel or mounted on a manual release
bracket. Note that an EPIRB with an automatic activation switch is disabled while
mounted in a manual release bracket and will not activate, even if it comes in contact
with water while in the bracket.
All type-approved EPIRBs are required to have a minimum duration of continuous
operation (battery life) of 24 hours; however, GMDSS requires a minimum duration of
continuous operation (battery life) of 48 hours.

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2.1.3
PLBs
PLBs are designed to be worn or carried by individuals rather than attached to an aircraft
or vessel. PLBs are smaller and lighter than ELTs and EPIRBs.
In some countries, PLBs are permitted for use in aviation and maritime situations but
are not necessarily designed for those environments. For example, PLBs are not required
to float in water, and even if a PLB does float in water, it may not keep its antenna
upright affecting the performance of the PLB.
PLBs are manually activated only and are required to have a minimum battery life of 24
hours.
2.1.4
SSAS Beacons
Cospas-Sarsat provides alerting services for the Ship Security Alert System (SSAS). An
SSAS beacon is activated in case of attempted piracy or terrorism and appropriate law
enforcement or military forces can then be dispatched. SSAS beacons are carried under
the IMO’s Safety of Life at Sea (SOLAS) Convention and are usually fitted in the bridge
of a ship.
SSAS beacon transmissions are processed in the same manner as distress alerts by the
Cospas-Sarsat System except that all messages relating to SSAS beacons are sent to the
Competent Authority (per SOLAS Convention, Chapter XI-2, Regulation 6.2.1).
Messages relating to SSAS beacons are not sent to a SAR Service unless the SAR
Service is also the Competent Authority for the country of registration encoded in the
beacon.
SSAS beacons can only be activated manually.
The SSAS contact details for ship security competent authorities are made available by
IMO Member States in the IMO Global Integrated Shipping Information System
(GISIS) database at https://gisis.imo.org/Public/Default.aspx. The Maritime Security
button, after appropriate login, provides access to “Proper recipients of SSAS alerts”.
States that allow use of SSAS beacons have also identified their ship security competent
authority to their associated MCC.

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Figure 2.2: The GISIS Maritime Security Website Interface
Figure 2.3: A Ship Security Alert System (SSAS) Beacon
2.1.5
ELT(DT)
Cospas-Sarsat has developed specifications for distress tracking of aircraft in-flight.
These Emergency Locator Transmitter for Distress Tracking beacons (ELT(DT)s) are
compliant with ICAO GADSS requirements for Autonomous Distress Tracking (ADT)

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to transmit accurate position information at least every minute, which should allow an
aircraft crash site to be located within six nautical miles (6 NM).
These requirements are described in the ICAO document 10054, the Manual on Location
of Aircraft in Distress and Flight Recorder Data Recovery. An ADT capability will be
required in most new commercial aircraft from the beginning of 2025.
Although an ELT(DT) will share many characteristics with existing ELTs, an ELT(DT)
may have some key differences:
•
activation by an automatic triggering event including unusual attitude, altitude or
speed or total loss of propulsion or thrust,
•
a more rapid transmission schedule,
•
every ELT(DT) will have a GNSS receiver and will be able to provide an accurate
GNSS position with each burst,
•
an ELT(DT) may be capable of being activated remotely by request from a
responsible agency. The remote activation would use the Return Link Service
(RLS) mechanism currently in development,
•
a cancellation message which will indicate the activation event is no longer active
(for example, the events generating the automatic triggering have returned to
normal values).
LUTs and MCCs have different processing rules for an ELT(DT); for example, locations
are not merged as the ELT(DT) is assumed to be on a fast-moving aircraft.
2.2
Characteristics of a 406-MHz Beacon
Cospas-Sarsat type-approved 406-MHz-beacon models are compatible with Cospas-Sarsat
satellites and comply with requirements of the 406-MHz First-Generation Beacon (FGB)
specification standard described in Cospas-Sarsat document C/S T.001 or the requirements of
406 MHz Second Generation Beacon (SGB) specification standard described in Cospas-Sarsat
document C/S T.018. Beacons are verified by thorough testing at Cospas-Sarsat accepted test
facilities for characteristics including compatibility of RF-characteristics and signal
waveform, digital message structure, beacon performance at different temperature conditions,
and minimum duration of continuous operation.
The list of type-approved 406 MHz beacon models is maintained by the Cospas-Sarsat
Secretariat and may be seen on the Cospas-Sarsat website.
Except for ELT(DT)s, most FGB types transmit a 5-Watt radio frequency burst of
approximately 0.5-second duration every 50 seconds, where the first burst occurs
approximately 50 seconds after activation of the beacon. Exceptions include ELT (AF)s
activated by G-switch or deformation sensor (for which the first-burst delay is no more than
15 seconds) and SSAS beacons. SGBs transmit on a varying schedule where the transmission
occurs less frequently as the duration of the transmission continues, as a means to conserve
the beacon’s battery capacity.

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For FGB and SGB ELT(DT)s, bursts are transmitted every 5 seconds in the first 120 seconds
after activation, and less frequently afterwards. ELT(DT)s start transmitting no more than 5
seconds after activation. All ELT(DT)s have a cancellation function, whereby activation of an
ELT(DT) can be cancelled by the same means by which it was initiated.
FGBs transmit distress signals on a specified frequency channel within the 406 MHz frequency
band (i.e., between 406.0 and 406.1 MHz) based on the beacon model (e.g., 406.025 MHz or
406.040 MHz). SGBs transmit distress signals across the allocated 406 MHz frequency band
(using “spread-spectrum” modulation) which provides protection against interference
occurring in specific portions of the 406 MHz frequency band. All SGBs have a cancellation
function.
The burst transmitted includes a digital message that contains information that can be used to
determine the Hex ID of the beacon.
2.3
The Beacon Message
The transmission from a distress beacon contains a digital message, as further described in
sections 2.3.1 and 2.3.2 below.
More detailed information on beacon coding can be obtained from Cospas-Sarsat document
C/S T.001, “Specification for [FGB] Cospas-Sarsat 406 MHz Distress Beacons”, Cospas-
Sarsat document C/S T.018, “Specification for Second-Generation Cospas-Sarsat 406 MHz
Distress Beacons” and  document C/S G.005, “Cospas-Sarsat Guidelines on 406-MHz Beacon
Coding, Registration and Type Approval”. Each document is available from the Cospas-Sarsat
website at www.cospas-sarsat.int.
2.3.1 The First Generation Beacon Message
The FGB “message” transmitted by the beacon is either a short message of 112 bits or a long
message of 144 bits.
Every FGB “message” begins with 24 bits of synchronisation data. These bits allow the start
of a valid FGB message to be identified. The remaining bits in the FGB message contain data
that is organised depending on the beacon coding protocol used for the beacon. Every FGB
“message” has a unique 15 Hex ID that includes the country of beacon registration.
Cospas-Sarsat has developed two major categories of FGB message protocols, User protocols,
and Location protocols:
•
User protocols are short FGB messages that consist of 112 bits of data that include the
beacon identification and other important SAR information, but do not allow for
encoded GNSS position data,
•
Location protocols are long FGB messages that consist of 144 bits of data that include
encoded GNSS position data (if available) as well as beacon identification data.
Both the User and Location protocols have various subtypes that provide a coding suited to
the individual beacon. For example, the EPIRB-MMSI Location Protocol contains a field to

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store the last six (6) digits of the MMSI (the country code provides the first three (3) digits for
the MMSI). A beacon with an EPIRB-MMSI protocol must be programmed with the known
MMSI of the vessel that carries the EPIRB. In contrast, the Serial Location Protocols contain
a field to store a 24-bit serial identification number. A beacon with a Serial Protocol can be
programmed by the manufacturer using serial numbers provided by the national beacon
authority.
A portion of the FGB ELT(DT) beacon message includes a rotating field, where some
transmissions include the three-letter designator (3LD) of the aircraft operator, and other
transmissions include a more precise GNSS location.
2.3.2 The Second Generation Beacon Message
The SGB message consists of 250 bits, of which 48 bits are within a rotating field type. The
use of a rotating field expands the amount of information that can be provided in the beacon
message by including certain kinds of information in one rotating field type and other kinds
of information in another rotating field type. Every SGB has a fixed identification consisting
of Type Approval Certificate (TAC) number and serial number that is independent of the
encoding of vessel or aircraft identification information in the beacon message. Every SGB
message has a unique 23 Hex ID that includes the country of beacon registration.
Compared to the FGB message, the additional bits in the SGB message enable additional
information to be provided, including a more precise GNSS position and the time that the
GNSS position was updated.
2.4
Hexadecimal Identity of a 406-MHz Beacon
Every beacon has a Unique Identification Number (UIN, also known as the beacon Hex ID).
The Hex ID for an FGB consists of 15 hexadecimal characters. For example,
3EF42AF43F81FE0 is the Hex ID of an Australian EPIRB. The Hex ID is displayed on the
beacon (see Figure 2.4). While a SGB has a 15 Hex ID that is backwards compatible with the
15 Hex IDs assigned to FGBs, the complete Hex ID for a SGB consists of 23 hexadecimal
characters.
Some information from the FGB or SGB message sent to RCCs and SPOCs within the SIT 185
text message is not available in the 15 Hex ID and 23 Hex ID.

2–8

Figure 2.4: Beacon with Hex ID 3EF42AF43F81FE0
The Hex ID is used operationally as the identification in Cospas-Sarsat distress alert messages
sent to Responsible Agencies. The Hex ID can be decoded to provide a variety of information
about the beacon, depending on the protocol used to encode it. Beacon coding protocols are
described in documents C/S T.001 and C/S T.018 (available on the Cospas-Sarsat website).
All Hex IDs include a country of registration provided as a MID (Maritime Identification
Digit) code, a three-digit identity. A list of all MID codes used by Cospas-Sarsat is provided
in Annex B of this document.
Hex IDs can be decoded using a software tool, also available on the Cospas-Sarsat website.
Figure 2.5 shows the result of decoding the Hex ID of the beacon from Figure 2.4 using the
decode tool on the Cospas-Sarsat website.

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2–9

Figure 2.5: Decode of Beacon 3EF42AF43F81FE0
2.5
Direction Finding on 406-MHz Beacons
Most 406 MHz FGBs and some SGBs transmit a quasi-continuous secondary signal on
121.5 MHz to enable suitably equipped SAR forces to home on the distress beacon using radio
direction finding techniques (see ICAO-IMO document 9731 known as the “IAMSAR
Manual”).
Homing on the 406-MHz burst is also being undertaken by some SAR authorities. Direction
finding on 406 MHz allows specially equipped SAR aircraft to accurately track the course to
the 406-MHz beacon, even if the signal is not continuously transmitted (see section 5.5.1 for
406 MHz beacon channels).
2.6
Return Link Service (RLS)
The Return Link Service (RLS) provides notification to a 406 MHz beacon that an alert
transmitted by the beacon has been detected by a LUT and distributed via the Cospas-Sarsat
MCC network to the MCC whose service area covers the beacon confirmed position (see
section 4.1.3 for a description of the MCC reference position). This service is intended to
provide acknowledgement of the reception of the alert message to persons in distress and is
only available for 406 MHz beacons coded to provide a return link.
Once notified that an RLS-capable beacon has been located, the RLSP interfaces to the Ground
Segment for transmitting return link messages to appropriate satellites, which, in turn, transmit
return link messages (RLMs) to the transmitting beacon. After receipt of the return link
message by the beacon, subsequent beacon transmissions include the return link message
receipt status, and a notification that includes the receipt status is distributed via the Cospas-
Sarsat MCC network to the designated RLSP. Once notified that the beacon has received the
return link message, the RLSP interfaces to the relevant ground segment which will cease
transmitting return link messages to satellites. Illustration of RLS is provided at Figure 1.1.
Further information on the Return Link Service is provided in document C/S R.012.

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2.7
GNSS Positions
A distress beacon with GNSS capability is able to transmit a GNSS position as part of its
beacon message. There are two mechanisms used to derive the GNSS position: either the
distress beacon has an internal GNSS receiver, or the distress beacon receives the GNSS data
from an external device that connects to the beacon.
If the distress beacon with GNSS capability does not provide a GNSS position (for example,
as the internal receiver cannot derive a GNSS position as it cannot track sufficient GNSS
satellites), default values are transmitted in the beacon message that indicate that there is no
encoded GNSS position available.
Distress beacons that transmit GNSS position data are coded with a Location protocol;
however, for FGBs, the particular Location protocol used affects the precision of the GNSS
position data that can be sent in a beacon message. Table 2.1 lists the precision for the FGB
Location protocols.
Table 2.1: Maximum Precision of the FGB Location Protocols
Protocol
Maximum Difference
Equivalent Distance at Equator
User Location
2 minutes
3.7 kilometres
Standard Location
2 seconds
60 metres
National Location
2 seconds
60 metres
RLS
2 seconds
60 metres
ELT(DT)
2 seconds
60 metres
In some situations, a beacon message may have errors that result in the LUT not being able to
produce a fine GNSS position. Instead, a coarse GNSS position is produced. Table 2.2 shows
the coarse precision for the Location protocols that may have a coarse precision GNSS
position.
Additional information:
According to document C/S T.001 section “Internal Navigation Device Performance”, for
FGBs coded with the Standard, National, or RLS Location protocols, the GNSS receiver
accuracy must be below 500m.
For suspected moving beacons, RCC operators should take into account that the beacon may
have drifted between the time the GNSS position has first been encoded in the beacon message
and the time a new GNSS position information is sent to the RCC or SPOC within a SIT 185
message including this GNSS position.
Specifically, for FGBs other than ELT(DT)s in in-flight mode:
1.
a maximum 52.5-second period (up to 120-second period for ELT(DT) in post-crash
mode) may occur between the time the GNSS receiver processes the GNSS position and
the time this position is encoded in the beacon burst and sent to the satellite,
2.
the refresh rate of the internal GNSS receivers is defined such as:

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a)
new beacons type-approved after 2022 should update their GNSS location
between 4 minutes 25 seconds and 15 minutes (i.e., the GNSS position provided
in a new SIT 185 message can be up to 15-minute old),
b)
new beacons type-approved between 2014 and 2022 should update their GNSS
location at least once every 30 minutes (i.e., the GNSS position provided in a new
SIT 185 message can be up to 30-minute old),
c)
it is not specified for beacons type-approved before 2014 (i.e., the GNSS position
provided in a new SIT 185 message can be more than 30-minute old).
Consequently, RCCs and SPOCs may receive SIT 185 messages updating the beacon
position information for which only the independent position (i.e., the DOA or the
Doppler position) has been updated, and therefore, still containing GNSS position
information that has been refreshed several minutes prior to the timestamp indicated in
the SIT 185 message.
For most beacons, the refresh rate of their internal GNSS receiver is available on the
Cospas-Sarsat website at https://www.cospas-sarsat.int/en/beacons-pro/experts-beacon-
information/approved-beacon-models-tacs?view=tac\_beacons, selecting the TAC
number and searching for the field “Encoded Position Data Update Interval [Fix]”.
(See also sections 5.3.8 “Source of GNSS Position Data” and 5.4.7 “Summary Guidance for
the Use of Position Data”.)
Table 2.2: Precision of the FGB Location Protocols with only Coarse Position
Protocol
Maximum Difference\*
Equivalent Distance at Equator
Standard Location
7 minutes 30 seconds
13.9 kilometres
National Location
1 minute
1.9 kilometres
RLS
15 minutes
27.8 kilometres
ELT(DT)
15 minutes
27.8 kilometres
* Assumes all available bits are used to provide the coarse position; see section 5.8.1.
Note: For SGBs, the precision of the GNSS position provided to Distress authorities is
approximately 10 metres.
Note: All ELT(DT)s are required to have a GNSS capability, and the GNSS location is normally
considered the primary location data for an ELT(DT). A DOA location is only provided for an
ELT(DT) if the MEOLUT is commissioned to provide DOA location for fast-moving beacons.
LEOLUT Doppler location is not provided to SAR services for ELT(DT)s.
2.8
Beacon Registration
As each beacon has a unique Hex ID, it is possible for each country to maintain a beacon
database to store supplementary information about a beacon, such as contact details for its
owner, other emergency contacts and details of any associated vessel or aircraft.

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A country can either provide its own beacon database or use the Cospas-Sarsat International
Beacon Registration Database (IBRD). Details of beacon databases can be found under the
“406-MHz-Beacon Registers” section of the Contact Lists on the Cospas-Sarsat web site.
2.9
International Beacon Registration Database (IBRD)
Despite the clear advantage of registration, a significant number of beacons are not properly
registered due to a lack of registration facilities in a number of countries. Furthermore, a
number of beacon registers do not have 24-hour points of contact easily accessible by
Responsible Agencies. Therefore, Cospas-Sarsat provides the International Beacon
Registration Database (IBRD).
2.9.1
International Regulations and Purpose of the IBRD
IMO policy, as stated in IMO Assembly Resolution A.887(21), adopted on
25 November 1999, provides in paragraph 2 that “every State requiring or allowing the
use of these GMDSS systems should make suitable arrangements for ensuring
registrations of these identities are made, maintained and enforced.” These arrangements
are further clarified in paragraph 12 which provides that “Every State should maintain a
suitable national database or co-ordinate with other States of their geographical area to
maintain a joint database”.
ICAO policy on registration of ELTs is contained in Chapter 5 of the ICAO Convention,
which provides that “States shall make arrangements for a 406 MHz ELT register.
Register information regarding the ELT shall be immediately available to search and
rescue authorities. States shall ensure that the register is updated whenever necessary.”
It is, therefore, the sole responsibility of States to provide the appropriate regulatory
environment, facilities and resources that are required for an effective registration
process. The IBRD is a means designed by Cospas-Sarsat to assist with the registration
process when, due to a lack of resources, States have not implemented facilities for a
national register. States may choose to selectively allow registration of beacons in the
IBRD by beacon type. The IBRD is also meant to assist States in making their
registration data available to SAR authorities on a 24-hour basis, seven days per week.
However, it is not designed to become the unique central repository for all beacon
registration data.
In providing the IBRD and making the IBRD available to States and users under their
jurisdiction, Cospas-Sarsat does not accept or take over the specific responsibilities of
States as stated by IMO and ICAO and declines all responsibilities or liabilities that
might be associated with the registration of any data in the IBRD, or its availability or
unavailability to SAR authorities.
When States choose to allow the registration of data from users under their jurisdiction
in the IBRD, or upload national registration data into the IBRD, they retain full and
exclusive responsibility for the integrity of such data, its accuracy and its availability to
SAR. In this regard, Cospas-Sarsat does not provide any guaranty as to the continuous
operation of the IBRD.

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2.9.2
Using the IBRD
The IBRD is designed to be freely available to users with no access to national
registration facilities and to Administrations who wish to avail themselves of the facility
to make their national beacon registration data more available to SAR services.
However, direct registration of beacons in the IBRD is not allowed for the country codes
of Administrations that have informed Cospas-Sarsat of their decision to control the
registration of beacons under their jurisdiction, whether in the IBRD or in their own
national registration databases.
The IBRD provides various levels of access to:
a)
beacon owners who wish to register their beacons when no registration facility
exists in their country and the responsible Administration has agreed to allow
direct registration in the IBRD;
b)
Administrations who control the registration of beacons identified with their
country code, but wish to make registration data available to international
Responsible Agencies via the IBRD;
c)
Responsible Agencies that need to access beacon registration data to efficiently
process distress alerts; and
d)
other authorised government entities or agencies for the purpose of controlling the
proper coding or registration of beacons.
The functional requirements for the IBRD are provided in the document C/S D.001
“Functional Requirements for the Cospas-Sarsat International Beacon Registration
Database” and the IBRD operations policy is defined in the document C/S D.004,
“Operations Plan for the Cospas-Sarsat International Beacon Registration Database”.
Access to the IBRD (www.406registration.com) is controlled by user codes assigned by
the Cospas-Sarsat Secretariat (www.cospas-sarsat.int) in accordance with Council
guidelines. Administrations wishing to use the IBRD should designate a National Point
of Contact. Cospas-Sarsat will accept designations from the Cospas-Sarsat
Representative or, for non-participating countries, the IMO or the ICAO Representative
for that country.
The Secretariat will provide each National IBRD Point of Contact with user
identifications and passwords to be used by:
•
National Data Providers for registration of beacons with their country code(s),
•
Responsible Agencies for IBRD queries,
•
authorised shore-based service facilities and inspectors to verify proper coding and
actual registration of the beacon.
These IBRD user identifications and passwords should be distributed within each
country under the responsibility of the National IBRD Point of Contact.

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In case of forgotten password, Responsible Agencies are invited to urgently contact their
National IBRD Point of Contact to retrieve their account details. If this is not possible,
contact the Cospas-Sarsat Secretariat (www.cospas-sarsat.int), noting the Cospas-Sarsat
Secretariat, situated in Montreal, Quebec, Canada, is defined as an administrative body
which is consequently not reachable 24 hours a day, seven days a week.
Detailed rules for accessing the IBRD are provided in the document C/S D.004.
Annex D contains a guide to assist a Responsible Agency using the IBRD.
2.10 Beacon Regulation
International regulations applicable to 406 MHz beacons are contained in document
C/S S.007; they include performance standards for 406 MHz beacons and guidelines to avoid
false alerts, information on beacon maintenance and testing, as well as guidance on beacon
protocols permitted by the country of registration.
2.11 Beacon Testing
406 MHz beacons are designed with a self-test capability for evaluating key performance
characteristics.  Initiating the beacon self-test function will not generate a distress alert in the
Cospas-Sarsat System.  However, it will use some of the beacon's limited battery power and
should only be used in accordance with the beacon manufacturer's guidance.
On occasions, a Responsible Agency may wish to activate an operational 406 MHz beacon;
for example, for SAR training purposes. As the beacon activation may be detected and treated
as a live incident by the Cospas-Sarsat System, all activations for non-distress purposes must
be approved in advance.
Requests to conduct a live beacon activation should be directed to the MCC that services the
location in which the activation is planned and, if the location is not within the country of
registration, the MCC responsible for the country in which the beacon is registered. When
making a request the following information should be provided:
•
Objective of the activation,
•
Description of the event,
•
Location,
•
Date, time and duration,
•
Beacon Hex ID (15 hexadecimal characters for an FGB or an SGB, or 23 hexadecimal
characters for an SGB),
•
Point of contact.
The responsible MCC will advise other MCCs of the planned beacon activation.
If the homing signal on the beacon will be active, relevant aviation authorities must also be
advised of the planned beacon activation.

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2.12 Inadvertent Alert
Cospas-Sarsat provides guidance on its website in case of inadvertent alerts occur, as follows:
“If a beacon is inadvertently activated, the beacon immediately should be turned off if
possible. If the beacon does not have an “off” function, it should be shielded from the sky by
placing it in a metal container (a solid metal box or a refrigerator, for example).
Because an alert likely will be received by the satellites even if the beacon was on for only a
short time, you should immediately contact the agency in your region responsible for
managing Cospas-Sarsat distress alerts to prevent unnecessary assignment of search and
rescue resources that may be needed for a real emergency somewhere else.
If your region has a Cospas-Sarsat Mission Control Centre in the "Contact Lists" (select “MCC
– Mission Control Centre” from the drop-down choices), please notify the centre in your area.
Otherwise select “SPOC – SAR Point of Contact” from the "Contact Lists" and notify them
of your inadvertent alert.
The "Contact Lists" are available under our Professional website.
There is no penalty for inadvertent activation of a beacon if there was no malicious intent.”
When reported to an MCC, the source of the alert should be categorized as depicted in the
graphic below.
Figure 2.6: Information Graphic on Sources of False Alerts
- END OF SECTION 2 -

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3–1

COSPAS-SARSAT SATELLITE SYSTEMS
Cospas-Sarsat uses three satellite systems, MEOSAR, LEOSAR and GEOSAR. Further
information on each satellite system can be found on the Cospas-Sarsat web site (www.cospas-
sarsat.int).
All the satellite systems have equipment known as a SAR payload placed on satellites that
have been designed for and are primarily used for other purposes. The two general categories
of equipment are:
1.
SAR Repeater (SARR): A SAR repeater receives a beacon transmission on 406 MHz
and retransmits the transmission on a different frequency, 1544 MHz. A SAR repeater
is sometimes called a bent pipe as it simply redirects the signal from the beacon back to
the earth for reception by a LUT. SARR instruments are carried on all Cospas-Sarsat
satellites. The satellite must have mutual visibility to the beacon and the LUT for
detection to occur.
2.
SAR Processor (SARP): A SAR processor receives a beacon transmission on 406 MHz
and stores the time of arrival, the received frequency and the beacon message in a buffer.
The data in the buffer is re-transmitted until overwritten by a more recent detection. The
retransmitted signal uses the 1544 MHz frequency. SARP instruments are carried only
on the LEOSAR satellites.
The three satellite systems are described in more detail in the following sections with a
description of the beacon detection and location data that can be determined by a LUT
associated with the satellite system.
Every satellite has a footprint on the Earth’s surface. The footprint is the area that the satellite
can see at sea level on the Earth’s surface. A satellite can only detect signals from beacons
that are within its footprint. The footprints shown in the following sections (for example,
Figure 3.2) show the maximum footprint with a zero-degree elevation.
3.1
MEOSAR
The MEOSAR space segment consists of SAR repeaters placed on the satellites of the Global
Navigation Satellite Systems (GNSS):
•
GPS satellites operated by the United States,
•
Russian Federation Glonass navigation satellites,
•
European Galileo navigation satellites
•
Chinese BDS navigation satellites.
These MEOSAR satellites orbit the Earth at altitudes between 19,000 and 24,000 kilometres,
a range considered as a medium-altitude Earth orbit. The radius of a MEOSAR satellite
footprint is about 6,000 to 7,000 kilometres. MEOSAR is designed to provide continuous
global coverage of the Earth.

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Figure 3.1: A Schematic View of the Galileo Constellation
(which is one of the constellations of the MEOSAR System)
The footprint of a GPS MEOSAR satellite is shown in Figure 3.2.
Figure 3.2: Footprint of a GPS MEOSAR Satellite
A MEOLUT tracks multiple MEOSAR satellites in view at the same time. Typically, a
MEOLUT has a number of antennas, and each antenna tracks a separate MEOSAR satellite.
r = 7,000 km
z = 24,000 km

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Upon receiving a transmission (a beacon burst) from a 406 MHz distress beacon via a
MEOSAR satellite, a MEOLUT will generally measure two key values: the Time of Arrival
(TOA) and the Frequency of Arrival (FOA). Assuming reception of beacon transmissions
through at least three distinct MEOSAR satellites, MEOLUT processing can provide a two-
dimensional (longitude and latitude) beacon location using a combination of time difference
of arrival (TDOA) and frequency difference of arrival (FDOA) computations. The location
computed by a MEOLUT is known as a difference of arrival (DOA) location. Three-
dimensional locations (i.e., with the addition of a computed altitude) are possible when the
beacon burst is relayed to a MEOLUT via four or more MEOSAR satellites.
Figure 3.3: An Overview of the MEOSAR System
In Figure 3.3 above, distress beacons (EPIRB, PLB or ELT) transmit a 406 MHz signal that is
detected by MEOSAR satellites in the BDS, GPS, Glonass and Galileo constellations. The
beacon transmission is relayed on 1544 MHz and detected by a MEOLUT. Beacon and
location data is sent from the MEOLUT to an MCC and then to a Responsible Agency to
initiate a response. The diagram also shows the Return Link Service offered by MEOSAR. A
message can be sent to particular MEOSAR satellites that are capable of sending a return link
message to a beacon with return link functionality.
In addition to calculating beacon locations using a single burst relayed by different satellites,
subsequent bursts can then be used to refine the beacon location. A location generated using
more than a single burst is known as a multi-burst location.
A MEOLUT may produce any of four possible forms of data:
1.
A beacon detection without location: A beacon is detected but there is no location data
associated with the detection.
2.
A beacon detection with a GNSS position: A beacon is detected and there is a GNSS
position encoded in the beacon message.

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3–4

3.
A DOA (Difference of Arrival) location: A beacon is detected, and using DOA
techniques, the MEOLUT is able to generate an independent estimate of the location of
the beacon. Typically, three or more satellites must detect the beacon to generate a DOA
location. A DOA location may be generated from a single burst from a beacon.
4.
A DOA location and a GNSS position: A beacon is detected; the beacon message
contains a GNSS position and a DOA position is also generated.
All ELT(DT)s are required to be capable of transmitting a GNSS location in the beacon
message. A DOA location is only provided to Distress Authorities for an ELT(DT) if the
MEOLUT is commissioned to provide DOA locations for fast-moving beacons.
Expected Accuracy for DOA Location
For each DOA location, an Expected Accuracy (i.e., estimated error) value is computed.
Information on the Expected Accuracy, also known as the Expected Horizontal Error (EHE),
is provided in the SIT 185 message as described in Paragraph 4.
This value is the radius of the circle centered on the DOA location that should contain the true
beacon location with a 95% probability. In other words, there is a 95% probability that the
location error, which is defined as the distance between the DOA location and the actual
beacon location, is lower than the Expected-Accuracy value.
The Figure below illustrates the configuration for which the DOA location error is lower than
the associated Expected-Accuracy value, with the corresponding confidence percentage.
Figure 3.4: DOA Location Error Smaller than the Associated
Expected-Accuracy Value
Additional details on the Expected Accuracy for DOA Location:
The Expected-Accuracy specification is further refined to ensure that Expected-Accuracy
values associated with a DOA location provide a confident reflection of the location error, and
in particular that the Expected Accuracy does not overestimate the location error in any
significant way.
This situation should
happen for
95% of the
MEOSAR DOA
locations
MEOSAR
DOA location
Actual beacon
location
Expected
Accuracy
Location
error

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In addition to the 95% confidence, Expected-Accuracy values must meet the following
requirement (per section 5.10 of document C/S T.019 – EHE). Namely, to ensure that the
associated Expected-Accuracy value does not underestimate the MEOSAR location error, the
DOA location error must be smaller than two times the associated Expected-Accuracy value
at minimum 99% of the time. In other words, there is only a maximum 1% probability that the
DOA location error is greater than two times the Expected-Accuracy value.
The Figure below illustrates this additional Expected-Accuracy-related boundary:
Figure 3.5: Additional Expected-Accuracy-Related Boundary
Figure 3.6: Probability of the Actual Beacon Location Being Within the Expected
Accuracy-Radius and Two-Times Expected Accuracy-Radius Circles
95% probability
that the location error
be below the
Expected-Accuracy
value
Expected
Accuracy
>99% probability that the location
error be below 2 x Expected
Accuracy
<1% probability that the
location error be above
2 x Expected Accuracy
2 x Expected
Accuracy
Contains the actual location with a 95% probability
Contains the actual location with a >99% probability

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3.2
LEOSAR
The LEOSAR satellites are low-altitude (between 700 and 1000 kilometres above the Earth)
spacecraft in near-polar orbits. As the LEOSAR satellite’s revolution takes about 105 minutes,
two successive paths of the same satellite are separated, due to the Earth rotation, by
approximately 25 degrees.
Figure 3.7: Four Passes of a LEOSAR Satellite
In Figure 3.7 above, at 1200 UTC, the satellite passes over Australia in a near-polar orbit. The
orbit can be in either direction (i.e., north to south, or south to north). At 0145 UTC (i.e., 105
minutes later), the satellite has completed a full polar orbit but due to the rotation of the Earth,
at 0145 UTC, the satellite is now approximately 25 degrees further west. A LEOSAR satellite
covers the surface of the Earth approximately every 12 hours.
The LEOSAR constellation has a minimum of four satellites; in June 2022, there were four
operational LEOSAR satellites in the constellation.
Global, non-continuous coverage of the Earth is achieved. The coverage is not continuous
because polar orbiting satellites can only view a relatively small portion of the Earth at any
given time. The radius of the footprint is about 3,000 kilometres. Figure 3.8 shows the footprint
of a LEOSAR satellite.

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3–7

Figure 3.8: Footprint of LEOSAR Satellite (Sarsat-10)
The LEOSAR satellites cannot detect distress alerts until the satellite is in a position where it
can receive transmission bursts from the distress beacon, in other words, when the beacon is
in the footprint of the satellite. The LEOSAR satellites transmit a distress alert that the
LEOLUT receives when the LEOLUT is in the footprint of the satellite. Since the LEOSAR
satellites also have a SAR Processor, the satellites store distress beacon information and
rebroadcast it continuously, so that the stored data can be received by a LEOLUT when the
satellite comes within view of the LEOLUT, thereby providing global coverage (with inherent
time delays).
r = 3,000 km
z = 900 km

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Figure 3.9: Global coverage of a LEOSAR satellite
In Figure 3.9 above, the footprint of a LEOSAR satellite is shown at two times. The first
footprint (on the left) only contains a beacon. The LEOSAR satellite detects the beacon and
stores the detection data in its SAR Processor. The second footprint (on the right) shows the
satellite at a later time. The footprint contains another beacon and a LEOLUT. The LEOSAR
satellite is able to download the detection data from the first beacon using the global coverage
provided by the SAR Processor. The second beacon, as it is in the same footprint as the
LEOLUT, can be directly relayed to the LEOLUT using the SAR Repeater on the LEOSAR
satellite. Detections using the SAR Repeater are known as local detections.
The LEOSAR system calculates the location of distress events using Doppler processing
techniques. Doppler processing is based upon the principle that the frequency of the distress
beacon, as “heard” by the satellite instrument, is affected by the relative velocity of the satellite
with respect to the beacon. By monitoring the change of the frequency of the received beacon
signal from different beacon transmission bursts, and, knowing the exact position and velocity
of the satellite, a LEOLUT is able to calculate two possible locations for the beacon. The two
locations are equidistant from the satellite at the time when the satellite was closest to the
beacon (the time of closest approach, or TCA).

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Figure 3.10: A Doppler Curve for a Hypothetical FGB
In Figure 3.10 above, the plot has the time of detection on the x-axis and the frequency of the
detection by the LEOSAR satellite on the y-axis. Each FGB burst (shown with the inverted
triangle) occurs approximately every 50 seconds. Due to the Doppler Effect, the beacon
frequency is initially detected at a higher frequency than the actual transmitted frequency, and
it then decreases as the satellite passes closer to the beacon. When the satellite is at the closest
point to the beacon (known as the TCA, or Time of Closest Approach), the frequency matches
the actual frequency of the beacon. By analysing the shape of the Doppler curve, a LEOLUT
can calculate the distance of the beacon from the satellite at the TCA, this produces two
possible locations for the beacon known as the Doppler A-side and Doppler B-side.
The two Doppler locations are known as the A-side and the B-side of the Doppler solution;
they are also known as the A-position and the B-position. The LEOLUT generates a
probability for each of the two Doppler locations taking into account the Doppler effect of the
earth’s rotation.
Time of Closest Approach

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3–10

Figure 3.11: Two Doppler Locations from a LEOSAR Satellite Pass
In Figure 3.11 above, note that the two locations (Doppler A and Doppler B) are equidistant
from the satellite at the time of closest approach (TCA).
The process of determining which of the two Doppler locations is the location of the beacon
is known as position confirmation (or ambiguity resolution). The Doppler location that is not
the location of the beacon is known as the mirror or image location.

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3–11

Figure 3.12: Confirmation by Two LEOSAR Passes
In Figure 3.12 above, this example continues the previous Figure 3.11. A second LEOSAR
satellite pass has produced two new Doppler locations, Doppler A2 and Doppler B2. The
location of the beacon would be confirmed by the matching of Doppler B1 (from the first
satellite pass) and Doppler A2 (from the second satellite pass). Both Doppler A1 and Doppler
B2 can now be determined to be mirror (image) locations.
A LEOLUT may use data from a GEOLUT to help generate the Doppler location for a given
beacon. This is known as LEO-GEO processing.
A LEOLUT may produce any of four possible forms of data:
1.
A beacon detection without location: A beacon is detected but there is no location data
associated with the detection. Typically, this is due to the LEOLUT receiving
insufficient bursts in order to perform the Doppler processing to produce locations.
2.
A beacon detection with a GNSS position. A beacon is detected and there is a GNSS
position encoded in the beacon message.
3.
Two Doppler locations. A beacon is detected, and using Doppler techniques, the
LEOLUT generates two possible estimates of the location of the beacon. The two
locations are known as the A-position and the B-position. The LEOLUT will also
generate a probability for each of these positions.
4.
Two Doppler locations and an encoded GNSS position. A beacon is detected, the beacon
message contains a GNSS position, and two Doppler locations are also generated.

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3–12

Although a LEOLUT may be able to compute a Doppler location for a beacon that is fast-
moving, the accuracy of that location is not expected to meet the requirements of the GADSS
for an ELT(DT), and all Doppler locations are filtered for ELT(DT)s. All ELT(DT)s are
required to be capable of transmitting a GNSS location in the beacon message, and the GNSS
location is considered to be the primary location data for the ELT(DT).
3.3
GEOSAR
The GEOSAR satellites orbit the Earth at an altitude of approximately 36,000 kilometres, with
an orbit period of 24 hours, thus appearing fixed relative to the Earth at approximately 0-
degree latitude (i.e., over the equator). A single geostationary satellite has a footprint with a
radius of approximately 7,500 kilometres and provides GEOSAR coverage of about one third
of the globe. Due to their positions over the equator, the GEOSAR satellites are unable to
detect beacons north or south of about 70 degrees of latitude. Figure 3.13 shows the footprint
of the GEOSAR satellite MSG-2.
Figure 3.13: Footprint of GEOSAR Satellite (MSG-2)
A GEOLUT may produce either of two possible forms of data:
1.
A beacon detection: A beacon is detected but there is no GNSS position data associated
with the detection.
2.
A beacon detection with an encoded GNSS position. A beacon is detected, and the
beacon message contains a position generated by the GNSS equipment in the beacon.
A GEOLUT has no means to compute an independent location for a beacon.
– END OF SECTION 3 –
r = 7,500 km
z = 36,000 km

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4–1

MISSION CONTROL CENTRES
Each MCC has a service area and provides beacon alert data to Responsible Agencies within
that service area. For example, the Norwegian MCC (NMCC) provides beacon alert data to
the Responsible Agencies in the following countries/regions: Denmark, Estonia, Faroe
Islands, Finland, Greenland, Iceland, Latvia, Lithuania, Norway, Poland and Sweden. Similar
information for all MCCs and their supported Responsible Agencies can be found on the
Cospas-Sarsat website.
MCCs are organized in a nodal network that allows efficient distribution of beacon alert data
around the world. This nodal network is comprised of six Data Distribution Regions (DDRs),
in which each DDR has a nodal (or hub) MCC that distributes alerts between other MCCs that
are not nodes; see Figure 4.1. MCCs send beacon alert data to a Responsible Agency outside
their service area using the MCC nodal network. For example, the Norwegian MCC (NMCC)
distributes an alert for the Algerian RCC via the nodal French MCC (FMCC), which then
distributes the alert to nodal Spanish MCC (SPMCC), which then distributes the alert the
Algerian MCC (ALMCC) which delivers the alert to the Algerian RCC.
Figure 4.1: A Schematic View of the MCC Network

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In Figure 4.1 above, there are six Data Distribution Regions (DDRs): the Western DDR
(WDDR), the Central DDR (CDDR), the South Central DDR (SCDDR), the North-West
Pacific DDR (NWPDDR), the Eastern DDR (EDDR) and the South-West Pacific DDR
(SWPDDR). Data distribution between DDR regions is performed by the nodal MCCs. Within
the CDDR, all MCCs are able to distribute data directly with other CDDR MCCs; in all other
DDRs, data distribution between MCCs in the DDR is also performed via the nodal MCC.
An MCC therefore receives beacon alert data from its local LUTs and also from other MCCs.
An MCC processes the beacon alert data with the objective of providing timely, accurate and
reliable beacon alert data to the relevant Responsible Agencies. The MCC filters out redundant
data to ensure that a Responsible Agency is not distracted or confused by unnecessary data.
The MCC network and the data processing rules are described in document C/S A.001 known
as the Data Distribution Plan (DDP).
4.1
General Principles
An MCC follows three basic principles when processing and forwarding data as follows.
4.1.1
Timeliness
An MCC provides timely data. The MCC does not wait for additional data before
sending data.
For example, if an MCC receives a beacon detection with no location, the MCC does
not wait before sending to a Responsible Agency, just in case no more data is received.
Instead the MCC would forward the beacon detection data to the Responsible Agency
and, if more data is received, would send the additional data to the Responsible Agency
later.
For aircraft distress tracking, ICAO requires that location data be provided at least once
a minute while the aircraft is in a potential distress situation. For this reason, all
ELT(DT) location data is forwarded to the associated MCC for processing.
4.1.2
Redundancy
An MCC attempts to minimize redundant data sent.
For example, if an MCC receives a GNSS position for a beacon, it will forward that
location to the appropriate Responsible Agency. If the MCC receives another beacon
detection with no location data (e.g., from another satellite), it will normally not forward
that data to the Responsible Agency. If the MCC received another detection with the
same GNSS position, it would similarly not forward this redundant location data.
As another example, if an MCC receives Doppler position data from two LEOLUTs for
satellite S-13 with the same TCA for the same beacon, then the MCC will not send the
second Doppler solution unless it has reason to believe that the new data may be of better
quality.

4–3

An MCC will send updates that would otherwise be considered redundant to allow a
Responsible Agency to know that a beacon is still active. For example, MEOSAR
position data will be sent every 15 minutes after position confirmation for beacons other
than ELT(DT)s, even if the latest detection does not provide better quality data.
4.1.3
Confirmation:
Beacon position data is unconfirmed until it has been confirmed on the basis of
information provided by two independent sources. Position confirmation requires that
two positions for a beacon are from independent sources and match within 20 kilometres
of each other, as specified in document C/S A.001. An MCC reference position is an
approximation of the beacon position generated or selected by the MCC, based on a
match of positions from independent sources within 20 kilometres. The MCC reference
position is used as the reference position to determine if subsequent position data is
deemed a position update or a position conflict, based on the 20-kilometre distance
threshold match. The MCC reference position may be further updated based on new
position data that matches the current MCC reference position within 20 kilometres.
A reference to a “position confirmed” alert or “position confirmation” in this document
does not imply that any specific position provided in the associated alert message is the
actual beacon position. Further information on the use of position data included in the
alert message is provided in section 5.4.
Two locations are independent if they are two different types of location, or for two
Doppler locations or for two DOA locations, if they are derived from different beacon
events, as outlined in the following table.
Table 4.1: Determining if Two Locations for a Beacon are Independent
GNSS
Doppler
DOA
GNSS
No
Yes
Yes
Doppler
Yes
Different satellites or time
(TCA) difference of at
least 20 minutes\*
Yes
DOA
Yes
Yes
Each satellite set has a
unique satellite or a time
difference of at least 30
minutes
* Two pairs of Doppler locations are not independent if each Doppler location matches a Doppler
location in the other solution; see “Unresolved Doppler Match” Section 4.2.6.
Note that the independence of two encoded GNSS position cannot be determined as the two
positions come from the same source, i.e., the GNSS unit on (or attached to) the beacon.
Section 7.22 provides clarifying examples of independence.
Position is not confirmed for ELT(DT)s, which are assumed to be fast-moving.

4–4

4.2
MCC Messages
The following sections describe the message types sent to a Responsible Agency by an MCC.
The complete messages are described in section 5, and examples are provided in section 6.
4.2.1
Initial Alert (Unlocated) and Initial Location Alert
An initial alert indicates that a beacon has been detected.
An initial alert with no location information is known as an unlocated beacon alert and
its message type is “INITIAL ALERT (UNLOCATED)”.
An unlocated beacon alert is sent to the Responsible Agencies associated with the
country of registration contained in the beacon message.
Although an unlocated beacon alert has no location data, the beacon message provides
useful data to a Responsible Agency. The beacon message contains the Hex ID of the
beacon. If the beacon is registered in the country’s beacon registration database or the
IBRD, the owner and emergency contacts can be determined. As well, some beacon
messages contain the MMSI of a vessel or a call sign of an aircraft which allows the
Responsible Agency to contact the vessel or aircraft associated with the beacon.
The message type for the first alert with location is “INITIAL LOCATED ALERT”,
unless there is a “position conflict” as described in section 4.2.3. The first located alert
may contain an MCC reference position, if the alert contains a GNSS position that
matches a Doppler or DOA position, as discussed in section 4.2.2.
The Responsible Agency informed of alerts with location data depends on the type of
beacon. For ELTs, EPIRBs and PLBs the location data is used to determine the SAR
Service informed of the alert. For SSAS beacons the location data does not affect the
Competent Authority informed as only the Competent Authority associated with the
country of registration is informed of an SSAS beacon activation.
For an ELT, EPIRB or PLB, an MCC sends an initial located alert to any SAR Service
relevant to the unconfirmed location data contained in the alert. For example, if a
LEOLUT generates two Doppler locations for a New Zealand EPIRB, one in the Fiji
RCC service area and another in the New Zealand RCC service area, the Australian
MCC will send an initial alert to both the Fiji RCC and the New Zealand RCC.

4–5

Figure 4.2: Two Doppler Locations from a LEOSAR Satellite Pass for an EPIRB
In the Figure 4.2 above, (that also appeared as Figure 3.11), a LEOSAR satellite has
produced two Doppler locations (Doppler A and Doppler B) for a New Zealand EPIRB.
As the Doppler A position is in the Fiji service area, the Fiji RCC will be sent an initial
alert with both Doppler locations. As the Doppler B position is in the New Zealand
service area, the New Zealand RCC will be sent an initial alert with both Doppler
locations.
Prior to position confirmation, every located alert is sent to each Responsible Agency
that previously received an alert for the beacon activation, as well the Responsible
Agencies responsible for a location in the new alert. This enables all involved
Responsible Agencies to coordinate a response.
A Responsible Agency may be able to use the unconfirmed location data along with
other information in responding to the incident. For example, additional information
from a phone call to an emergency contact using the beacon registration details or a flare
sighting near an unconfirmed location may assist the tasking of resources.
4.2.2
Position Confirmed Alert
A position confirmed alert contains an MCC reference position, which is the result of
two matching independent locations, as described in section 4.1.3 above. When a
position is confirmed, the message type is “POSITION UPDATE ALERT” if an alert
with position information was previously sent, or “INITIAL LOCATED ALERT” if
no position information was previously sent. The presence of an MCC reference position
indicates that position is confirmed.

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A position confirmed alert is sent to all Responsible Agencies that have received alert
messages about the beacon activation.
For example, if an initial alert from an EPIRB is sent to the Fiji RCC and the New
Zealand RCC as the alert had two Doppler locations generated by a LEOLUT, when the
location is confirmed as in New Zealand, the alert will be sent to both the Fiji RCC and
the New Zealand RCC. The position confirmed alert informs the Fiji RCC that the
beacon position has now been confirmed to be outside the Fiji RCC service area.
Figure 4.3: Confirmation of LEOSAR Data by a MEOSAR Detection
In the Figure 4.3 above, DOA location data from the MEOSAR system has confirmed
the beacon location with the Doppler B1 location. As MCC reference position is in the
service area of New Zealand, the New Zealand RCC will be sent the alert. As an initial
alert had been sent to the Fiji RCC due to the earlier Doppler A1 location, the alert will
also be sent to the Fiji RCC.
The first alert sent from an MCC to a Responsible Agency provides an MCC reference
position when the first alert contains position data (DOA or Doppler) and a matching
GNSS position.
The method used by the MCC to generate the MCC reference position from the matching
independent locations is not defined by Cospas-Sarsat. Instead, the specifications state
that this position may be formed by a merge of matching locations which may be based
on a weighting factor assigned to each matching location. Each Responsible Agency

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4–7

should consult with its supporting MCC to obtain information on the method used to
generate the MCC reference position by that MCC.
Position is not confirmed for ELT(DT)s, which are assumed to be fast-moving. If an
ELT(DT) alert is sent with matching GNSS and DOA positions, then the message type
is “DOA POSITION MATCH”.
4.2.3
Position Conflict Alert
Except for ELT(DT)s, if an MCC receives new location data that does not match any of
the previous location data for that beacon within 20 kilometres, then the new location
data is labelled as “in conflict”. For ELT(DT)s, position data in previous alerts is not
referenced in the processing of new position data, thus a position conflict can only occur
for an ELT(DT) if the GNSS and DOA positions in the new alert are “in conflict”.
The MCC filters some conflict data (for example, if the new location data is of lesser
quality) but otherwise sends a position conflict alert to indicate that the new location
data does not match previously sent location data.
A fast-moving beacon (for example, on an aircraft) other than an ELT(DT) will typically
generate an initial alert followed by a series of conflict alerts, as all the alerts after the
initial alert will not match. The trail of conflicts may provide a path for the fast-moving
beacon.
It is possible for a Responsible Agency to receive a conflict alert as the first message.
For example, if an MCC receives a DOA location and a GNSS position as the first alert
for a beacon, and if the DOA location and the GNSS position do not match, the MCC
will send a conflict message to the relevant Responsible Agencies.
Prior to position confirmation, for ELTs, EPIRBs and PLBs, if non-matching locations
are in the area of responsibility of different SAR Services, all the SAR Services would
receive a conflict alert.
4.2.4
Position Update Alert
An MCC will send an update alert if it receives beacon detection data that is not
redundant. Cospas-Sarsat has a very detailed definition of when an update is sent, but
from the Responsible Agency perspective, an update will be sent when the MCC has
additional data or better-quality data, or to indicate that the beacon is still active and
transmitting.
An update can be sent before and after confirmation of the location.
Prior to position confirmation, a new alert with DOA position that is otherwise
redundant will be sent every five (5) minutes for all beacon types except ELT(DT)s.
To prevent too many MEOSAR alerts from being sent to a Responsible Agency after
position confirmation, a MEOSAR alert with DOA position matching the MCC

4–8

reference position that is not better quality will only be sent every 15 minutes. A
MEOSAR alert with DOA position that does not match the MCC reference position and
is not better quality will only be sent every ten (10) minutes. An alert with a better-
quality DOA position (based on the expected horizontal error) is always sent, as
specified in document C/S A.001. Position is not confirmed for ELT(DT)s, which are
assumed to be fast-moving.
For all beacon types except ELT(DT)s, an updated alert with GNSS position is sent if
the new GNSS position differs from previously sent GNSS position by three (3) to
twenty (20) kilometres or, for an FGB, if the new GNSS position is refined (i.e., more
precise) and no previous GNSS position was refined.
In general terms, a new alert for an ELT(DT) is sent to the Responsible Agency every
five (5) seconds within the first 30 seconds after beacon activation. More specifically, if
the “reference” detection time of the new ELT(DT) alert is within 30 seconds of the
earliest “reference” detection time received, then the alert is sent if:
a) no other alert has been sent with a reference time within three (3) seconds of the new
alert’s reference time; or
b) the new alert has GNSS position (and no other alert with GNSS position has been
sent with a reference time within three (3) seconds of the new alert’s reference time);
or
c) the new alert has DOA position (and no other alert with DOA position has been sent
with a reference time within three (3) seconds of the new alert’s reference time).
Note that ELT(DT)s transmit every five (5) seconds for the first 120 seconds after
activation, so the three (3)-second threshold noted above effectively results in alerts
being every five (5) seconds.
The new alert is also sent if, based on service area information available to the MCC, it
contains DOA or GNSS position located in a service area for which the Responsible
Agency has not previously been sent an alert.
In addition, if the current reference (detection) time is at least ten (10) minutes more
recent than the reference time for all previously sent alerts, then the MCC sends the
“best” solution with a reference time more recent than the reference time for all
previously sent alerts, where the priority is given to a GNSS position (SGB) or refined
GNSS position (FGB). Until MCCs have implemented distribution of the “best” new
solution, they send a new alert with GNSS or DOA position, if the new reference time
is at least ten (10) minutes after the reference time for all previously sent alerts.
4.2.5
Notification of Country of Beacon Registration Alert
A Notification of Country of Registration (NOCR) alert is sent to the SAR Service
associated with the country of registration in the beacon message. An NOCR is not sent
to the Competent Authority for an SSAS alert as all SSAS alert messages are sent to the

4–9

Competent Authority associated with the country of registration and hence there is no
need for an NOCR alert.
For example, if a PLB with a country of registration of New Zealand is detected outside
the New Zealand Search and Rescue Region (SRR), the RCC in New Zealand will be
sent an NOCR alert.
An MCC that processes an ELT, EPIRB or PLB location in its service area will generate
the NOCR and send the NOCR through the MCC network as required.
An NOCR alert is similar to an unlocated alert in that both alerts are sent based on the
country of registration. However, an NOCR alert is only sent when there is a location
associated with a beacon; an unlocated initial alert is sent when there is no location
associated with the beacon.
An NOCR alert permits a SAR Service to commence a search for beacon registration
details before a request is received from the SAR Service that is responding to the beacon
incident. It also enables the national SAR Service in the country of registration to offer
assistance, as appropriate, for the rescue of their fellow citizens.
4.2.6
Unresolved Doppler Position Match Alert
An Unresolved Doppler Position Match occurs when the two Doppler locations from
one beacon event match the two Doppler locations from another beacon event prior to
position confirmation. Since neither Doppler location can be ruled out as the actual
position, neither of the two Doppler locations is confirmed by the second pair of Doppler
locations.
Figure 4.4 shows an unresolved Doppler match that occurred in 2011. One LEOSAR
satellite, Sarsat S-08, tracked on the red path and produced two Doppler locations
(shown as purple dots). LEOSAR satellite Sarsat-11 tracked on the purple path at a later
time and produced two Doppler locations (shown as red dots). The unresolved Doppler
match does not confirm a location (as both of the two possible locations are still
potentially valid). Note that in 2011 the matching distance for position matches was 50
kilometres; but has since changed to 20 kilometres.

4–10

Figure 4.4: Example of an Unresolved Doppler Match
4.2.7
Interferer Alert
Some MCCs transmit 406 MHz interferer alerts to SAR Services using the SIT 185
message format.
The International Telecommunication Union (ITU) has allocated the 406 MHz band for
low power distress beacons. Nevertheless, there are unauthorised signal sources in
various areas of the world radiating in the 406.0 – 406.1 MHz range. Interferers degrade
the performance of the Cospas-Sarsat System and reduce the ability of the System to
detect and locate real beacon messages. Suitably equipped LUTs in the Cospas-Sarsat
System are used to detect and locate the source of some of these interferers. Unlike the
processing of 406 MHz digital beacon signals, no identification code is available from
an interferer. An interfering source can only be identified by determining its location.
Persistent interferers are reported by MCCs to ITU through their national spectrum
management agencies.
4.2.8
User Cancellation Alert
A user cancellation message is sent when three separate cancellation messages have been
received from the beacon with detect times within 110 seconds, with no intervening non-
cancellation messages. The FGB and SGB specifications require that the user cancellation
function only be activated by the same source that originally activated the beacon.

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4–11

4.3
Alerts with Invalid or Suspect Data
In some cases, the beacon detection data or location data is invalid or may be inaccurate for
various reasons. The SIT 185 message sent to a Responsible Agency by an MCC will indicate
these situations.
4.3.1
Transmissions with an Invalid Beacon Message
The data transmitted in the message from a distress beacon includes error-correcting
codes that allow a LUT to detect and to fix some errors in the data. If there are too many
errors in the beacon message, the LUT cannot correct the errors and the message is
treated as invalid. As well, for all beacon messages that the LUT receives correctly, the
MCC performs additional validation of the beacon message and if data has invalid values
(e.g., an invalid country code), the whole beacon message is also treated as invalid.
An MCC will send the Hex ID associated with an invalid beacon message, but the
Responsible Agency should note that the Hex ID is unreliable and should be treated with
caution. Other data, including GNSS position data, from the beacon message is not sent
to the Responsible Agency as the data may be invalid.
A beacon alert with an invalid beacon message does include the DOA or Doppler
position data. Even if the beacon message is invalid, the DOA and Doppler location data
are still reliable.
4.3.2
Suspect Doppler Locations
Doppler locations may be suspect for a number of reasons. An MCC will note any such
Doppler locations when sent to a Responsible Agency.
If the LEOSAR satellite that detected the beacon has recently completed a satellite
manoeuvre, the location of the satellite in space may be different from the location used
by the LEOLUT to calculate the Doppler locations. Doppler locations with a detect time
(TCA) within 24 hours after a satellite manoeuvre are noted as suspect when sent, if the
expected location error resulting from the manoeuvre may exceed ten (10) kilometres.
The LEOLUT calculates the Doppler locations using time and frequency data from the
satellite. Factors that contribute to the quality of the locations produced include the
number of beacon bursts, the angle of the satellite to the beacon and the relationship of
the TCA to the timing of the bursts. Any Doppler locations generated by poor quality
data are noted as suspect and should be treated with caution by a Responsible Agency.
An MCC performs a satellite footprint check on all locations. The footprint check
ensures that any location associated with an alert was visible to the satellite(s) that
reported the beacon. The footprint check uses a minus five (5) degree elevation in its
calculation to provide some assurance that the location is indeed outside of the footprint.
If the MCC determines that one of the Doppler locations in a LEOSAR detection is
outside the footprint of the LEOSAR satellite that detected the beacon, the message sent
will note that the location data is suspect.

4–12

4.3.3
Uncorroborated MEOSAR Alerts
A MEOSAR alert detected by only a single satellite and only a single beacon burst with
no previous alert for the beacon activation that contains data from a different beacon
burst or satellite is deemed uncorroborated and is treated as suspect. Normally these
uncorroborated detections are only sent to a Responsible Agency if:
a)
the beacon is a Distress Tracking ELT (ELT(DT));
b)
the reporting MEOLUT meets relevant requirements for generating processing
anomalies; or
c)
it is known that the beacon ID associated with the MEOSAR alert is registered.
If such a detection is sent to a Responsible Agency, the message will note that this is a
single uncorroborated detection and note if the associated beacon ID is registered. Such
alerts should be treated with caution since they may not correspond to actual beacon
transmissions.
The validity of an uncorroborated MEOSAR alert (i.e., the validity of the associated
beacon ID and/or encoded position) can be substantiated by the presence of
corroborating information, such as:
a)
another alert for the same beacon ID;
b)
beacon registration data for the specific beacon ID (and information provided
about the use of the beacon by the point of contact identified in the beacon
registration);
c)
a vessel or aircraft ID in the alert message (and related registration information for
this ID); or
d)
correlation between the beacon type indicated on the alert message and the beacon
type(s) designated for the associated Type Approval Certificate (TAC) number (if
a TAC number is provided on the alert message).
Relevant information for “Type Approval Certificate Numbers” is located on the
Cospas-Sarsat
website
https://www.cospas-sarsat.int/en/beacons-pro/experts-
beaconinformation/approvedbeacon-models-tacs?view=tac\_beacons.
4.3.4
Suspect DOA Locations
DOA locations provided include an estimate of accuracy. For example, a DOA location
with an accuracy estimate of 20 nautical miles should be within 20 nautical miles of the
beacon, 95% of the time.
Any DOA location with a large accuracy estimate should be treated with caution.
If a satellite footprint check indicates that the DOA location is outside the footprint of
any of the MEOSAR satellites that detected the beacon, the message sent will note that
the location is suspect.

4–13

4.3.5
Suspect GNSS Positions
A GNSS position that fails the satellite footprint check is suppressed and is not
transmitted.
- END OF SECTION 4 -

5–1

COSPAS-SARSAT DISTRESS MESSAGES
An MCC sends beacon alerts to Responsible Agencies in SIT 185 format. A SIT (Subject
Indicator Type) 185 is a plain text message with information regarding the beacon activation.
Examples of SIT 185 messages are presented and analysed in section 6. Figure 5.1 contains
an example SIT 185 message for an FGB.
080401Z JAN 2017
FROM AUMCC
TO RCC WELLINGTON
BT
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 12590  AUMCC REF C00F429578002C1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER – PLB
SERIAL NO 0042334
HEX ID C00F429578002C1
COUNTRY OF BEACON REGISTRATION 512/NEWZEALAND
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 08 JAN 17 0354 UTC BY SARSAT 10
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A - 41 14 S  172 31 E  PROB 79 PERCENT
DOPPLER B - 48 20 S  135 51 E  PROB 21 PERCENT
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0282 MHZ
TAC NO 0176
BEACON MODEL – STANDARD COMMS, AUSTRALIA MT410, MT410G
6.  REMARKS NIL
END OF MESSAGE
Figure 5.1: A Sample SIT 185 Message
SIT 185 messages may include a preamble. The format of the preamble is determined by the
sending MCC. In Figure 5.1, the four-line preamble includes the day and time of transmission
in UTC and the identification of the originating MCC (AUMCC) and recipient (the RCC
Wellington). The characters BT (for Begin Transmission) indicate the end of the preamble in
the sample message above. As the format of the preamble is dependent on the MCC and is not
part of the formal specification for SIT 185 messages, no preamble will be shown in following
examples of SIT 185 messages.

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5–2

When information with respect to a message field is not available, or is unknown or irrelevant,
dependent upon the message type and beacon protocol, the distress message will indicate
“NIL”  for that message field, or, for certain message fields, the message field may be omitted.
A Cospas-Sarsat SIT 185 message consists of six (6) paragraphs. Table 5.1 lists the paragraphs
of a SIT 185 message.
Table 5.1: Message Content for SIT 185 Messages
PARAGRAPH\#
TITLE
1.
MESSAGE TYPE
M
2.
CURRENT MESSAGE NUMBER
M
MCC BEACON REFERENCE
M
3.
BEACON MESSAGE INFORMATION
M
TYPE OF BEACON
O
IDENTIFICATION
O
BEACON HEX ID
M
COUNTRY OF BEACON REGISTRATION
O
BEACON NUMBER
O
HOMING SIGNAL
O
ACTIVATION TYPE
O
SOURCE OF GNSS POSITION DATA
O
EMERGENCY CODE
O
4.
ALERT POSITION INFORMATION
M
DETECTION TIME & SPACECRAFT
M
GNSS
POSITION,
TIME
OF
UPDATE
AND
ALTITUDE
O
MCC REFERENCE POSITION
O
DOA POSITION AND ALTITUDE
O
A POSITION & PROBABILITY
O
B POSITION & PROBABILITY
O
5.
OTHER INFORMATION
M
DETECTION FREQUENCY
M
OTHER ENCODED INFORMATION
O
6.
REMARKS
M
END OF MESSAGE
M
Notes:
1. "M" means that the field is mandatory
2. "O" means that the field may be omitted if the value is NIL.
5.1
Paragraph 1: Message Type
For an alert from a ship security (SSAS) beacon, the message type begins with “SHIP
SECURITY COSPAS-SARSAT”.
For an alert from a Distress Tracking ELT (ELT(DT)), the message type begins with
“DISTRESS TRACKING COSPAS-SARSAT”.

5–3

For all other beacon types, the beacon alert message type begins with “DISTRESS COSPAS-
SARSAT”.
The message types are described in section 4.2 and are listed here:
•
“INITIAL ALERT (UNLOCATED)”
•
“INITIAL LOCATED ALERT”
•
“POSITION CONFLICT ALERT”
•
“DOA POSITION MATCH ALERT”
•
“POSITION UPDATE ALERT”
•
“NOTIFICATION OF COUNTRY OF BEACON REGISTRATION ALERT”
•
“USER CANCELLATION ALERT”
•
“UNRESOLVED DOPPLER POSITION MATCH ALERT”
•
“ROTATING FIELD UPDATE ALERT”
•
“UPDATED ALERT UNLOCATED”
5.2
Paragraph 2: Current Message Number and MCC Beacon Reference
The current message number is a sequential message number assigned by the transmitting
MCC to each message sent to a specific Responsible Agency. Responsible Agencies should
ensure that they do not miss any message numbers.
The MCC beacon reference is a unique designator supplied by the MCC to identify all
messages sent for that beacon. Some MCCs use an integer and other MCCs use the beacon 15
Hex ID for this message field.
Responsible Agencies wishing to discuss a particular alert with an MCC can assist the MCC
by quoting the message number and the MCC reference designator of the alert.
5.3
Paragraph 3: Beacon Message Information
This paragraph provides key information about the beacon derived from the 406 MHz beacon
message. Any message field in this paragraph with a value “NIL” may be omitted. If the
beacon message is invalid, then the only message field provided without a “NIL” value in this
section is the Hex ID and the following note is included:
“DATA DECODED FROM THE BEACON MESSAGE IS NOT RELIABLE”
5.3.1
Type of Beacon
The beacon type is the general category of the beacon protocol used to code the beacon.
The protocol is provided as well as any identification fields. For example, the last six
digits of the MMSI are shown for beacons coded with an EPIRB-MMSI protocol.

5–4

It should be noted that some beacons are coded inappropriately for the environment in
which they are used. For example, there have been real world examples of EPIRBs being
used as PLBs in the Himalayan Mountains. Some countries allow PLBs to be coded with
an ELT protocol for use on an aircraft.
Examples of the different identification fields are shown in the following sections.
5.3.1.1
Serial Number
A serial number is assigned by the country of registration. The serial number does
not provide any further identification by itself; the relevant beacon database of the
country of registration must be searched for further details.
BEACON TYPE USER LOCATION – EPIRB (NON FLOAT FREE)
SERIAL NO 0106717
5.3.1.2
Aircraft Operator Designator and Serial Number
Aircraft operator designators are provided by ICAO in the airline designators
document, published as ICAO document 8585 – “Designators for Aircraft
Operating Agencies, Aeronautical Authorities and Services”. These designators
are 3-letter codes like BAW for British Airways or QFA for QANTAS.
Each operator designator can have a serial number from 1 to 4095.
BEACON TYPE STANDARD LOCATION – ELT
AIRCRAFT OPERATOR DESIGNATOR AND SERIAL NO QFA 0543
5.3.1.3
Aircraft 24-Bit Address
The ICAO 24-bit aircraft address is allocated to States to uniquely identify aircraft
worldwide. The Appendix to Chapter 9 of the ICAO Annex 10, Aeronautical
Communications document provides the worldwide scheme for the allocation,
assignment and application of aircraft addresses. The 24-bit address is presented
as six hexadecimal characters in the Cospas-Sarsat distress alert message.
BEACON TYPE STANDARD LOCATION – ELT
AIRCRAFT 24-BIT ADDRESS 7C5E8A ASSIGNED TO AUSTRALIA
5.3.1.4
Radio Callsign
The Radio callsign allocations can be obtained from the ITU website: www.itu.int.
BEACON TYPE USER LOCATION - EPIRB
RADIO CALLSIGN VHN-259

5–5

5.3.1.5
MMSI
The “all” nine-digit MMSI is formed by adding the country code provided in the
country of registration field to the six trailing digits provided in the “MMSI” vessel
identification field.
BEACON TYPE STANDARD LOCATION - EPIRB
MMSI ALL 9 DIGITS 563004940
HEX ID 4664026980FFBFF
COUNTRY OF BEACON REGISTRATION 563/SINGAPORE
In the above example, the “all” nine-digit MMSI is 563004940 composed of the
country code 563 and the six trailing digits 004940.
5.3.1.6
MMSI with AIS ID
The SGB message may contain a MMSI and an automatic identification system
(AIS) ID. The AIS is an automatic tracking system that uses transceivers on ships
to improve maritime safety. The AIS ID always has a prefix of “974”, which is
not encoded in the SGB message. A sample is provided below.
BEACON TYPE - EPIRB
MMSI 366123456
EPIRB-AIS ID 974 0123
TAC 12260 SERIAL NO 13750
HEX ID ADD4BF935B61 574A670007B
COUNTRY OF BEACON REGISTRATION 366/USA
5.3.2
Identification
Other information may be decoded from the 406 MHz message and may be used by the
servicing MCC to provide information with respect to an aircraft 24-bit address country
assignment and its registration marking.
AIRCRAFT 24-BIT ADDRESS 7C5E8A ASSIGNED TO AUSTRALIA
5.3.3
Beacon Hex ID
The Hex ID is the 15 character hexadecimal representation of a beacon identification
code as described in section 2.4.
5.3.4
Country of Beacon Registration
The three-digit country code, based on the list provided by the International
Telecommunication Union (ITU) is provided, followed by the name of the country of
beacon registration.
A list of the three-digit country codes is given at Annex B of this document and is also
provided on the Cospas-Sarsat web site (www.cospas-sarsat.int).

5–6

5.3.5
Beacon Number
For the first beacon on board the vessel or aircraft, the message field will be identified
as zero (0). Other beacons on board the vessel or aircraft will be identified as 1 to 63 and
A to Z. All the other programmed information will remain the same (e.g., MMSI, Radio
Callsign, Aircraft Identifier, etc.).
Different protocols will allow different numbers of beacons to be recorded.
5.3.6
Homing Signal
Homing Signal Interpretation:
•
“NIL”, means no homing transmitter,
•
“121.5”, means a 121.5 MHz homing signal in addition to the 406 MHz satellite
signal,
•
“MARITIME”, means Maritime 9 GHz Search and Rescue Radar Transponder
(SART) in addition to 406 MHz,
•
“NIL OR NOT 121.5”, means no homing transmitter or homing transmitter
other than 121.5 MHz
•
“OTHER”, means a nationally assigned homing signal has been included in the
beacon.
5.3.7
Activation Type
A beacon can be activated either manually or automatically.
The activation type provides information with respect to the switching mechanism built
into the beacon; i.e., some beacons can only be activated manually, and others can be
activated automatically or manually. For example, a float-free EPIRB will indicate
“automatic or manual” activation in the distress alert message, an ELT (including an
ELT(DT)) can be either activated automatically because of a strong acceleration or
deceleration on the “G” sensor, or manually by the crew in the cockpit. An ELT(DT)
can also be activated due to the aircraft avionics detecting an anomalous condition, in
which case the activation type indicates “AUTOMATIC BY EXTERNAL MEANS
(AVIONICS)”.
Ship security alert messages always indicate “MANUAL” activation as SSAS beacons can
only be activated manually.
The type of beacon activation is not available in all beacon coding protocols.
For FGB User Protocol beacons, this information is not protected, i.e., is not subject to
automated error detection and correction, and thus should be treated with caution.

5–7

5.3.8
Source of GNSS Position Data
This message field indicates whether the GNSS location data was provided to the beacon
by an internal or external GNSS device.
The update rate for a beacon with an internal GNSS device depends on the model of
beacon. (See also sections 2.7 “GNSS Positions” and 5.4.7 “Summary Guidance for the
Use of Position Data”).
Regardless of a beacon model’s designed GNSS position update period, its GNSS
position may not be updated if the beacon’s visibility to GNSS satellites is significantly
obstructed.
An FGB designed to accept position data from an external device prior to beacon
activation should be provided with position data by the external device at intervals not
longer than 20 minutes for EPIRBs and PLBs and 1 minute for ELTs. If the navigation
input fails or is not available, the FGB will retain the last valid position for four (4) hours
after which the GNSS position will be set to default values.
SGB ELT(DT)s retain the last valid GNSS for 24 hours after which the GNSS position
will be set to default values.
Note: If the beacon receives its encoded location from an external navigation system, it
is possible that this location may have been derived from a source that is not a satellite
(GNSS) navigation system.
5.3.9
Emergency Code
A provision exists in some beacon coding protocols to indicate the nature of distress in
accordance with the International Maritime Organisation (IMO) maritime emergency
codes. These codes can indicate “Fire/Explosion”, “Flooding”, “Collision”,
“Grounding”, “Listing”, “in Danger of Capsizing”, “Sinking”, “Disabled and Adrift” or
“Unspecified Distress”.
A provision also exists in the beacon coding to indicate non-maritime emergencies, and
these include an indication of a fire, if medical assistance is required, or if disabled.
This message field is not protected; i.e., it is not subject to automated error detection and
correction. As a consequence, the information provided for this message field should be
treated with caution.
Currently there are no beacons type-approved with this capability and in most cases no
emergency code is available. However, there are some beacons that have been coded by
default to indicate “unspecified distress”.

5–8

5.4
Paragraph 4: Alert Position Information
Detection information (including detection time and satellite) and position information
associated with the beacon alert is provided in Paragraph 4.
5.4.1
Detection Time and Spacecraft ID
For MEOSAR alerts, the detection time provided with the prefix “DETECTED AT” is
the time of the first burst. As a MEOSAR detection may be detected by many satellites,
the Spacecraft ID is shown as “MEOSAR”. As the alert may be a multi-burst detection,
the time of the last MEOSAR burst in this alert is on the following line.
For LEOSAR alerts with Doppler location, the detection time is the time of closest
approach (TCA) of the satellite to the beacon. Note that the actual time that the LEOSAR
satellite first detected the beacon can be either slightly before or after the TCA, but the
TCA provides a common point in time for processing. The time is followed on the same
line by “LEOSAR” and the identity of the satellite which provided the alert data. The
LEOSAR satellites are identified as Sarsat or Cospas. For a combined LEOSAR-
GEOSAR solution, the identity of the LEOSAR satellite is given.
For LEOSAR alerts without Doppler location, the detection time is the time of the last
beacon burst.
For GEOSAR alerts, the detection time is the time of the first beacon burst. The time is
followed on the same line by “GEOSAR” and the identity of the satellite which provided
the alert data. The GEOSAR satellites are identified as GOES (Geostationary
Operational Environmental Satellite; USA), MSG/MTG (Meteosat Second/Third
Generation; EUMETSAT), Electro-L and Louch-5 (Russia), and INSAT and GSAT
(India).
Except for a MEOSAR alert with matching first and last detection times on the alert
message, an alert may include multiple bursts, in which case it cannot be assumed that
the GNSS position for an ELT(DT) was computed at the reported detection time.
5.4.2
Position Information (General)
An example of position information is shown below:
4.  ALERT POSITION INFORMATION
GNSS - NIL
MCC REFERENCE - NIL
DOA - 05 10.1 S  178 01.4 E  ESTIMATED ERROR 002 NMS
ALTITUDE NIL
DOPPLER A - NIL
DOPPLER B - NIL

5–9

There may be multiple locations shown in this field. A position confirmed alert will have
an MCC reference position and will also show the locations from the most recently
processed detection used to confirm the location. Similarly, a position update alert sent
after the position confirmation will have the current MCC reference position and will
also show the locations from the most recently processed detection.
Noting that the uncertainty of a refined GNSS position is two (2) seconds of latitude and
longitude (about 60 metres at the equator), a refined GNSS position is generally the most
accurate position for a beacon, provided that the GNSS position has been updated
recently or the beacon is not moving. Further information about GNSS position updates
is provided in section 5.3.8. In accordance with document C/S A.001, a refined GNSS
position is not confirmed (i.e., not confirmed as representing the actual beacon position)
until it matches a Doppler or DOA position within twenty (20) kilometres; this
requirement for a match with position data from an independent source addresses the
possibility that the initial GNSS position after beacon activation may be inaccurate (e.g.,
provide a previously computed GNSS position) due to a beacon malfunction.
Summary guidance for the Use of Position Data is provided in section 5.4.7.
Section 6 provides examples of real distress alerts and illustrates how the position data
is shown in this field. If the value for a specific position field is “NIL”, then the
associated data line may be omitted from the alert message.
5.4.3
GNSS Position, Time of Update and Altitude
The GNSS field is the latitude and longitude of the GNSS position. The GNSS update
time for an FGB is always shown as “within 4 hours of detection time” as the system
does not record the time that the GNSS position was generated. If a GNSS position of
the FGB has not updated within four hours on a beacon, the beacon stops transmitting
the GNSS position (and would be shown as “NIL” in the GNSS field). As discussed in
section 2.7, the precision of the GNSS position is dependent on the FGB protocol used
and whether a fine or coarse GNSS position is received by the LUT.
For SGBs, information about time of the GNSS location is provided, if available:
•
for ELT(DT)s, “TIME OF GNSS POSITION UPDATE:” followed by the
update time,
•
otherwise, “TIME SINCE GNSS LOCATION GENERATED: [nn]
MINUTES”.
For SGBs and FGB ELT(DT)s, if the altitude is available, it has the title “ALTITUDE
OF GNSS LOCATION” and is provided in both metres and feet.
If GNSS position currency information is available for an FGB ELT(DT), then the
following text is included:
“UPDATE TIME WITHIN [AAAA] OF DETECTION TIME” where “[AAAA]” is:
•
- “0 - 2 SECONDS”,

5–10

•
- “2 - 60 SECONDS”, or
•
- “1 MINUTE TO 4 HOURS”
5.4.4
MCC Reference Position
If there is an MCC reference position, the latitude and longitude are provided. This
position may be formed by a merge of matching locations, which may be based on a
weighting factor assigned by the MCC to each matching location.
5.4.5
DOA Position and Altitude
The DOA field provides the latitude and longitude of the DOA location, the estimated
error (i.e., expected accuracy) of the DOA location in nautical miles, and the altitude of
the DOA location from the mean sea level in metres. If the estimated error value is
greater than 277.8 kilometres (150 nautical miles), the error is shown as “OVER 150
NMS”. If the estimated error is not available or the reporting MEOLUT is not
commissioned to meet MEOSAR IOC requirements for DOA position accuracy and the
reliability of the expected horizontal error (EHE) as specified in document C/S T.020,
then the estimated error is shown as “UNKNOWN”. Further information about the DOA
position expected accuracy is provided in section 3.1 above.
The DOA altitude is not verified as part of MEOLUT commissioning and is indicated
by “NIL” or omitted.
5.4.6
Doppler A and B Positions and Probability
The “DOPPLER A” and the “DOPPLER B” fields provide any Doppler locations and
their probabilities. Further information about the reliability and expected accuracy of
Doppler location data is provided in Paragraph 5.
5.4.7
Summary Guidance for the Use of Position Data
GNSS Position
The GNSS position is transmitted by the beacon and determined by a navigation source
in, or connected to, the beacon (such as aircraft/vessel navigation consoles).
The GNSS position uncertainty that is provided in the “OTHER INFORMATION”
section of the alert message may vary, as per section 2.7 above.
The GNSS position transmitted in a beacon distress message might be a stale/old
position if the beacon subsequently becomes detached from an external navigation
source providing the position to the beacon.
Note: The GNSS position is primarily derived from global navigation satellite systems
(such as GALILEO, GPS, GLONASS, BDS, etc.) but could, on some occasions, include

5–11

positions from other external, non-GNSS based systems, which may be subject to
degradation of accuracy over time.
MCC Reference Position
An approximation of the beacon position estimated or selected by the MCC, based on a
match of positions from independent sources within 20 kilometres. The MCC Reference
position is used to determine if subsequent position data is deemed a position update or
a position conflict, based on the 20-kilometre distance threshold match. The MCC
reference position may be further updated based on new position data that matches the
current MCC reference position within 20 kilometres. There is no standard algorithm
for computing the MCC Reference position; contact the associated MCC for further
information about its algorithm
DOA Position
A position computed by a MEOLUT, based on signals received from multiple MEOSAR
satellites relaying the same beacon transmissions.
A MEOLUT can normally provide a position from a single beacon transmission.
MEOLUTs typically calculate an estimated error for each position, which is the radius
of the circle that is centered on the estimated location and contains the true location with
a probability of about 95%.
When the estimated error is not available, then in the case of a stationary beacon, the
positions shall meet the following accuracy requirements:
a)
at least 90% should be within five (5) kilometres, from a single beacon
transmission; and
b)
at least 95% should be within five (5) kilometres, after ten (10) minutes of beacon
transmissions.
When a DOA location is computed from a single beacon transmission, then the two
detection times provided in Paragraph 4 of the alert message are the same.
Finally, the beacon altitude may also be provided by the MEOLUT. The DOA altitude
is not verified as part of MEOLUT commissioning and is set to “NIL” or omitted until
further notice.
Doppler Position
A Doppler position is computed by a LEOLUT based on signals received from a
LEOSAR satellite. If a Doppler position is provided without the “SUSPECT” reliability
warning (in the “OTHER INFORMATION” section of the alert message), the Doppler
position should be accurate within five (5) kilometres 95% of the time. The SIT 185
message provides the probability that each of two provided Doppler positions (i.e., an
“A” position and a “B” position) correspond to the real position.

5–12

The “OTHER INFORMATION” section of the SIT 185 message provides further
information about position data that is “SUSPECT” (e.g., due to a satellite footprint
check or a satellite manoeuvre).
Note: More detailed information on SIT 185 message content can be obtained by
contacting your supporting MCC, or by reviewing document C/S A.002 on the Cospas-
Sarsat website (www.cospas-sarsat.int).
5.5
Paragraph 5: Other Information
Other information obtained by the MCC that may be valuable to SAR authorities. This
information includes:
a)
Doppler position reliability if suspect due to less than ideal satellite pass geometry
processing parameters;
b)
Doppler position reliability if suspect due to a satellite manoeuvre (when an error greater
than ten (10) kilometres is suspected);
c)
Doppler or DOA position reliability if suspect due to failure of satellite footprint check;
d)
determination of an image (incorrect) position using a footprint check prior to Doppler
location ambiguity resolution; and
e)
if the beacon message is invalid then the warning is given that the data decoded from
the beacon message is not reliable.
If Doppler position is provided without a warning that its reliability is suspect, then it is
expected that the Doppler position is accurate within five (5) kilometres. Note that a nominal
Doppler solution (i.e., one generated when satellite pass geometry is ideal, as specified in
document C/S T.005), is required to be accurate within five (5) kilometres in 95% of cases.
The MCC may also provide additional information in this section; for example, the identity of
the LUT that processed the beacon message or beacon database registry information.
5.5.1
Detection Frequency
The frequency is the actual frequency of the beacon transmission as determined by the
LUT. As of 2025, Cospas-Sarsat distress FGBs were using 406.025 MHz,
406.028 MHz, 406.031 MHz, 406.037 MHz, 406.040 MHz and 406.076 MHz channels
(an updated list of frequencies in use can be found at Annex H of document C/S T.012).
If the actual frequency is not available for an FGB, then the value “406 MHZ” is
provided. The center frequency value “406.05 MHZ” is reported for SGB alerts
without DOA position.
Knowledge of the individual frequencies may assist Responsible Agencies when tasking
aircraft with a 406 MHz direction finding capability.

5–13

5.5.2
Other Encoded Information
Other information may be decoded and provided from the 406 MHz message, including:
•
Cospas-Sarsat beacon type approval certificate (“TAC”) number from which the
beacon model and manufacturer can be ascertained,
•
the precision of the GNSS position.
When GNSS position data is present, its uncertainty, which is the maximum possible
difference between the GNSS position processed by the beacon and the GNSS position
transmitted in the SIT 185 Message, is provided in the following format in Paragraph 5,
where the degree of uncertainty is provided in Table 5.2.
“GNSS POSITION UNCERTAINTY PLUS-MINUS [X MINUTES/SECONDS] OF
LATITUDE AND LONGITUDE.”
Table 5.2: GNSS Position Uncertainty
Uncertainty
Comments
2 MINUTES
FGB User location protocol
2 SECONDS
ELT(DT), RLS, standard and national location protocol,
maximum resolution (FGB only)
15 MINUTES ELT(DT), RLS protocol, minimum resolution (FGB only)
30 MINUTES FGB Standard location protocol, minimum resolution\*
4 MINUTES
FGB National location protocol, minimum resolution\*
10 METRES
SGBs
* For standard and national location protocols, the reported degree of uncertainty assumes that
the associated FGB is coded with an older methodology, in which the last bit available to report
a coarse GNSS position may not be used. The actual uncertainty is one fourth the reported
uncertainty (i.e., 7 minutes 30 seconds for standard location protocol and one (1) minute for
national location protocol, as noted in section 2.6), if it is known that the associated beacon is
coded with a newer methodology in which all bits available to report a coarse GNSS position
are used. Based on the Type Approval Certificate (TAC) number associated with the beacon
model, as provided in Paragraph 5, further information about the uncertainty of a coarse GNSS
position may be available on the Cospas-Sarsat website link for “Type Approval Certificate
Numbers”.
If an SGB has no GNSS position capability, “BEACON DOES NOT HAVE GNSS
POSITION CAPABILITY” is indicated in the alert message.
For SGBs, other information is provided from the beacon message, if available:
•
“ELAPSED TIME SINCE ACTIVATION: [nn] HOURS”, where the time since
activation is truncated, and

5–14

•
“REMAINING BATTERY CAPACITY: BETWEEN [nn] AND [nnn]
PERCENT”.
If information on beacon characteristics is available for the TAC number encoded in the
beacon message, then this statement is provided: “BEACON CHARACTERISTICS
PER TAC DATABASE PROVIDED IN A SEPARATE MESSAGE”. The
corresponding information on beacon characteristics is provided in a SIT 985 message.
5.6
Paragraph 6: Remarks
Additional information may be provided at the discretion of the originating MCC in this
paragraph and may include value-added information from the MCC operator.
For ship security alerts, advice is included that the alert will need to be processed in accordance
with relevant security procedures.
In alert messages for an ELT(DT), the following is included in the alert: “THIS DISTRESS
TRACKING MESSAGE IS BEING SENT TO APPROPRIATE SAR AUTHORITIES”
and “PROCESS THIS ALERT ACCORDING TO RELEVANT REQUIREMENTS”.
Administrations should follow defined national SAR procedures for responding to the
activation of an ELT(DT). As the alert is likely emanating from an aircraft still in flight,
“DISTRESS TRACKING” alert messages should be sent to an Aeronautical RCC (ARCC)
which should rapidly liaise with relevant ATSU(s) and airline operator(s) as specified in
dedicated annexes to the ICAO Convention, IAMSAR Manual (ICAO document DOC 9731),
and GADSS documentation.
The following is included in the alert message for Return Link Service (RLS) beacons:
•
“THIS BEACON HAS [RLS-ID] RETURN LINK CAPABILITY
where RLS-ID identifies the RLS provider (e.g., GALILEO or GLONASS) when available.
The alert message for a RLS beacon also indicates:
•
RLM
TYPE-[X]
[RECEIVED/CAPABLE]
([AUTO/MANUAL]
ACKNOWLEDGEMENT)
where:
-
[X] is replaced with “1” or “2”. TYPE-1 provides “AUTOMATIC”
acknowledgement and TYPE-2 provides “MANUAL” acknowledgment; only
TYPE-1 beacons are currently authorized.
-
“[RECEIVED/CAPABLE]” is replaced with “RECEIVED” or “CAPABLE”,
-
“[AUTO/MANUAL]” is replaced with “AUTOMATIC” or “MANUAL”.

5–15

5.7
End of Message
This text is added to the message to give an unambiguous indication to the message recipient
that there is no further information.
- END OF SECTION 5 -

6–1

EXAMPLES OF BEACON INCIDENTS
This section contains examples of beacon incidents and the distress alerts sent to Distress
authorities. Some examples are based on real-world incidents; others have been modified or
created to demonstrate specific aspects of beacon processing. All examples are for FGBs,
except when it is explicitly noted that an example is for an SGB.
Space and Ground Segment situations described in these examples do not reflect the current
status and should be used for training purpose only.
6.1
An Unlocated Detection to a Position Confirmed Update
This incident shows how information relating to an EPIRB with the Hex ID:
BEEE4634B00028D is presented to a SAR Service as four consecutive SIT 185 messages.
The four SIT 185 messages demonstrate a common sequence of messages received by a SAR
Service. Figure 6.1 provides a graphical depiction of the message sequence.
Figure 6.1: Sequence of Four SIT 185 Messages Sent to a SAR Service
in Example 6.1

![Image 1 from page 70](/images/cospas-sarsat/G-series/G007/G007_page_70_img_1.png)

6–2

6.1.1
An Initial (Unlocated) Alert
1.  DISTRESS COSPAS-SARSAT INITIAL ALERT (UNLOCATED)
2.  MSG NO 00189  AUMCC REF BEEE4634B00028D
3.  BEACON MESSAGE INFORMATION
BEACON TYPE  SERIAL USER - EPIRB (NON FLOAT-FREE)
SERIAL NO 101676
HEX ID BEEE4634B00028D
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE NIL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 15 MAR 23 1230 UTC BY MEOSAR
ALERT LAST DETECTED AT 15 MAR 23 1230 UTC
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A – NIL
DOPPLER B - NIL
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0280 MHZ
6. REMARKS NIL
END OF MESSAGE
Notes:
1.
The type of alert is listed in Paragraph 1. This example is an initial alert. An initial alert
that does not have a position is often called an “unlocated” alert.
2.
Paragraph 2 lists the message number of 00189 and an MCC beacon reference. The
message number allows all messages between an MCC and a SAR Service to be
uniquely identified. A SAR Service can use the message number to check that there are
no missing messages. The MCC beacon reference is used to identify the beacon incident;
all alerts for this beacon incident will use the same beacon reference. The Australian
MCC uses the Hex ID of the beacon as the reference, other MCCs may use a different
reference system.
3.
The initial alert contains the beacon Hex ID in Paragraph 3. In the example, the Hex ID
also appears in Paragraph 2 as the AUMCC reference.
4.
Paragraph 4 contains the detection time of the first MEOSAR burst of “15 MAR 23
1230 UTC”. The next data line contains the detection time of the last MEOSAR burst
used in this alert. In this example, the times of the first and last burst are the same,
indicating that this is a single burst solution.

6–3

5.
Paragraph 3 lists the country of registration. For this example, the country of registration
is Australia.
6.
This alert was an unlocated detection, and Paragraph 4 lists no positions. The positions
are all shown as “NIL” to indicate that no position information is available. If the value
for a specific position is “NIL”, then the associated data line may be omitted from the
alert message.
As this is an unlocated detection, the alert is sent to the SAR Service associated with
country of registration for the beacon. In this example, the alert is sent to the Australian
JRCC as the beacon has Australia as the country of registration.
7.
Paragraph 3 contains information about the beacon. In this case, the serial number of the
EPIRB is “101676”. The serial number of the EPIRB can be used to look up the beacon
in the Australian beacon registry. If the beacon is registered, the contact details may
allow the Australian JRCC to commence responding to this initial detection.

6–4

6.1.2
An Initial Alert with a MEOSAR Location
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 00190  AUMCC REF BEEE4634B00028D
3.  BEACON INFORMATION
BEACON TYPE SERIAL USER - EPIRB (NON FLOAT-FREE)
SERIAL NO 101676
HEX ID BEEE4634B00028D
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 15 MAR 23 1230 UTC BY MEOSAR
ALERT LAST DETECTED AT 15 MAR 16 1237 UTC
DOA - 17 47.2 S  146 04.5 E  ESTIMATED ERROR 005 NMS
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0280 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
This is an initial alert with a location. The location shown in Paragraph 4 is a DOA
(Difference of Arrival) or MEOSAR location. The location is shown with an estimated
error, and, in this example, the beacon will be located within five (5) nautical miles of
the location, 95% of the time.
2.
The DOA Altitude value is not provided until further notice and is omitted in this sample
message.
3.
The DOA Position Conflict Alert message below is sent because the distance between
the DOA position which was independently processed by the Cospas-Sarsat System, and
the GNSS position which was processed by the GNSS receiver associated with the FGB
ELT(DT), is at least 20 km.
4.
Fields in paragraphs 3 and 4 with a “NIL” value have been omitted.
5.
The reference in Paragraph 2 (the Hex ID of the beacon) is used by the SAR Service to
associate this alert to the same beacon incident as the alert shown in section 6.1.1.
6.
Paragraph 4 contains the detection time of the first burst, “15 MAR 23 1230 UTC”
and the detection time of the last burst, “15 MAR 23 1237 UTC”. As the two times
are different, this a multi-burst solution.

6–5

6.1.3
A Position Confirmed Alert
1.  DISTRESS COSPAS-SARSAT POSITION UPDATE ALERT
2.  MSG NO 00191  AUMCC REF BEEE4634B00028D
3.  BEACON MESSAGE INFORMATION
BEACON TYPE  SERIAL USER - EPIRB (NON FLOAT-FREE)
SERIAL NO 101676
HEX ID BEEE4634B00028D
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 15 MAR 23 1248 UTC BY MEOSAR
ALERT LAST DETECTED AT 15 MAR 23 1248 UTC
MCC REFERENCE - 17 47.5 S  146 06.2 E
DOA - 17 47.6 S  146 07.4 E  ESTIMATED ERROR 005 NMS
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0280 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
A position confirmed alert (in this case, with title “Position Update Alert”) is sent when
two independent locations match, as described in section 4.1.3. In this example, the DOA
(MEOSAR) location shown in Paragraph 4 has matched the location in the previous alert
in section 6.1.2. See the description of “Confirmation” in section 4.1.3.
2.
The MCC reference position shown in Paragraph 4 is determined based on a weighting
factor assigned to each previous DOA location. The AUMCC merges DOA locations to
produce an MCC reference position. Other MCCs may use other methods to determine
the MCC reference position.

6–6

6.1.4
A Position Confirmed Update Alert
1.  DISTRESS COSPAS-SARSAT POSITION UPDATE ALERT
2.  MSG NO 00194  AUMCC REF BEEE4634B00028D
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER - EPIRB (NON FLOAT-FREE)
SERIAL NO 101676
HEX ID BEEE4634B00028D
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 15 MAR 23 1301 UTC BY MEOSAR
ALERT LAST DETECTED AT 15 MAR 23 1301 UTC
MCC REFERENCE - 17 47.6 S  146 05.3 E
DOA - 17 47.9 S  146 04.5 E  ESTIMATED ERROR 002 NMS
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0280 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
If the SAR service is configured to receive ongoing updates after position confirmation,
the MCC will send an update to the MCC reference position in a number of conditions;
e.g., if a solution with matching DOA position is processed with a data time at least 15
minutes after the most recent data time of previous message with DOA position, or if a
Doppler solution is processed for a new beacon event.
2.
In this example, the updated MCC reference position was computed based on a
weighting factor assigned to each previous DOA position.

6–7

6.2
From Unlocated Alert to Position Confirmation
The following incident has similar SIT 185 messages to those in section 6.1 but demonstrates
detections from the GEOSAR and LEOSAR systems. The incident shows the SIT 185
messages sent to a SAR Service for an EPIRB with Hex ID BEEE43FCF8001AD. The three
SIT 185 messages for this incident are depicted in Figure 6.2.
6.2.1
A GEOSAR Unlocated Alert
1.  DISTRESS COSPAS-SARSAT INITIAL ALERT (UNLOCATED)
2.  MSG NO 12301  AUMCC REF BEEE43FCF8001AD
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER - EPIRB (NON FLOAT FREE)
SERIAL NO 0065342
HEX ID BEEE43FCF8001AD
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 27 APR 24 1557 UTC BY GEOSAR INSAT-3D
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A - NIL
DOPPLER B - NIL
5.  OTHER INFORMATION
LUT ID 4191 BANGALORE GEOLUT, INDIA
DETECTION FREQUENCY 406.0286 MHZ
TAC 0107
BEACON MODEL - ACR, USA RLB-32
6.  REMARKS NIL
END OF MESSAGE
Figure 6.2: Sequence of Three Beacon Messages Sent in Example 6.2

![Image 1 from page 76](/images/cospas-sarsat/G-series/G007/G007_page_76_img_1.png)

6–8

Notes:
1.
Paragraph 4 states that the detection was by satellite INSAT-3D, a geostationary
satellite. The beacon is expected to be located within the footprint of the INSAT-3D
satellite which is centred at (0° N, 082° E). See Figure 6.3 below.
2.
No position information is shown in Paragraph 4, since this is an unlocated initial
detection of the beacon.
Figure 6.3: Footprint of the GEOSAR INSAT-3D Satellite
In the Figure 6.3 above, the outline of the footprint is shown by the yellow line. The
position of the INSAT-3D satellite is shown by the yellow diamond in the centre of
the footprint.

![Image 1 from page 77](/images/cospas-sarsat/G-series/G007/G007_page_77_img_1.png)

6–9

6.2.2
A LEOSAR Initial Alert
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 12307  AUMCC REF BEEE43FCF8001AD
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER LOCATION - EPIRB (NON FLOAT FREE)
SERIAL NO 0065342
HEX ID BEEE43FCF8001AD
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 27 APR 23 1653 UTC BY LEOSAR SARSAT 12
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A - 43 04.04 S  147 15.75 E  PROB 83 PERCENT
DOPPLER B - 51 45.19 S  167 48.58 W  PROB 17 PERCENT
5.  OTHER INFORMATION
THE B POSITION IS LIKELY TO BE AN IMAGE POSITION
DETECTION FREQUENCY 406.0277 MHZ
TAC 0107
BEACON MODEL - ACR, USA RLB-32
LUT ID 6011
6. REMARKS NIL
END OF MESSAGE
Notes:
1.
Paragraph 4 indicates that the detection was made by LEOSAR satellite Sarsat-12, a
when it passed by the beacon. Paragraph 5 reports that the detection was further received
by the LEOLUT 6011 in Cape Town, South Africa when Sarsat-12 and this LEOLUT
were in mutual visibility.
2.
Paragraph 5 indicates that the B position is the likely image position. Figure 6.4 shows
the Doppler locations on a map. The B position is outside the footprint of INSAT-3D,
the geostationary satellite that provided the first detection. Although image
determination provides a strong indicator that the A position is the “real” position, image
determination is not used by Cospas-Sarsat to provide confirmation of a position.

6–10

Figure 6.4: LEOSAR Initial Alert
The yellow line is the track (path) of the LEOSAR satellite Sarsat-12. The orange
outline is the footprint of Sarsat-12 at the TCA (Time of Closest Approach) of the
beacon. The two Doppler locations generated by this pass are shown. The location
of the LEOLUT 6011 in Cape Town, South Africa is also shown.

![Image 1 from page 79](/images/cospas-sarsat/G-series/G007/G007_page_79_img_1.png)

6–11

6.2.3
A LEOSAR Position Confirmed Alert
1.  DISTRESS COSPAS-SARSAT POSITION UPDATE ALERT
2.  MSG NO 63523  AUMCC REF BEEE43FCF8001AD
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER LOCATION - EPIRB (NON FLOAT FREE)
SERIAL NO 0065342
HEX ID BEEE43FCF8001AD
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
HOMING SIGNAL 121.5
ACTIVATION TYPE MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 27 APR 23 1716 UTC BY LEOSAR SARSAT 10
MCC REFERENCE - 43 03.25 S  147 15.96 E
DOPPLER A - 43 02.89 S  147 15.91 E
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0276 MHZ
TAC 0107
BEACON MODEL - ACR, USA RLB-32
LEOLUT 6011
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
The position has been confirmed using data from a second LEOSAR detection (satellite
Sarsat-10 shown in Paragraph 4) that matches a Doppler position from the previous
initial alert. See the description of “Confirmation” in section 4.1.3.
2.
The matching Doppler A position is provided along with the MCC reference position in
Paragraph 4. In this example, the MCC reference position computed by the MCC from
the initial and subsequent alerts is biased to the location that is more likely to be accurate
(as the magnitude of the error ellipse is less). The Doppler A position information
provides for a means to ensure that the MCC processing is normal and enables the SAR
Service to reference the individual (un-merged) position in planning its SAR response.
3.
The A position of the Sarsat-10 pass matches the A position of the initial alert from
Sarsat-12 which results in an MCC reference position being computed (see Figure 6.5).

6–12

Figure 6.5: Confirmation of Position Using a LEOSAR Alert
In the Figure 6.5 above, the yellow line is the track of LEOSAR satellite Sarsat-10.
The orange outline is the footprint of Sarsat-10 at the TCA for this beacon. The two
Doppler locations generated by this pass are shown. The Doppler A position for this
detection matches the Doppler A position from the previous detection (see Figure 6.4)
and confirms the location.

![Image 1 from page 81](/images/cospas-sarsat/G-series/G007/G007_page_81_img_1.png)

6–13

6.3
A Position Confirmed Alert as the First Alert
In this example, the first alert received by the SAR Service is a position confirmed alert. The
presence of a position in the field titled “MCC REFERENCE” indicates that position is
confirmed, based on the matching of two independent locations, as described in section 4.1.3
above.
6.3.1
A Position Confirmed Alert
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 00463  AUMCC REF 3EEC7B9076FFBFF
3.  BEACON MESSAGE INFORMATION
BEACON TYPE STANDARD LOCATION – EPIRB
SERIAL NO 2107
HEX ID 3EEC7B9076FFBFF
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
HOMING SIGNAL 121.5
GNSS POSITION PROVIDED BY INTERNAL DEVICE
4.  ALERT POSITION INFORMATION
DETECTED AT 03 APR 23 1124 UTC BY MEOSAR
ALERT LAST DETECTED AT 03 APR 23 1124 UTC
GNSS - 25 40.07S  113 39.00E
UPDATE TIME WITHIN 4 HOURS OF DETECTION TIME
MCC REFERENCE - 25 39.5 S  113 37.3 E
DOA - 25 39.5 S  113 37.3 E  ESTIMATED ERROR 004 NMS
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0402 MHZ
GNSS POSITION UNCERTAINTY PLUS-MINUS 2 SECONDS OF
LATITUDE AND LONGITUDE
6. REMARKS NIL
END OF MESSAGE
Notes:
1.
Paragraph 4 shows that this alert has a DOA position and a GNSS position.
2.
As the DOA position and GNSS position match (the two positions are approximately
three (3) kilometres apart and so are within the twenty-kilometre matching criterion) and
are independent, the position is confirmed.
3.
The AUMCC does not merge a DOA position and a GNSS position to produce an MCC
reference position. Instead, the AUMCC uses the DOA position as the MCC reference
position. Other MCCs may merge the DOA and GNSS position to produce the MCC
reference position.
4.
Paragraph 5 provides the uncertainty of the GNSS position as two (2) seconds of latitude
and longitude, about 60 metres at the equator. A GNSS position with two (2) seconds of
uncertainty is generally the most accurate position for a beacon, provided that the GNSS
position has been updated recently or the beacon is not moving.

6–14

6.4
A MEOSAR Alert Confirmed by a LEOSAR Alert
The beacon with the Hex ID: C809C70A34D34D1 is first detected with a MEOSAR location
that is later confirmed with LEOSAR location data. Figure 6.6 depicts the two messages.
Figure 6.6: The Two SIT 185 Messages in Example 6.4
6.4.1
An Initial Alert from the MEOSAR System
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 05714 AUMCC REF C809C70A34D34D1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE USER - EPIRB USER
MMSI ALL 9 DIGITS 576774000
HEX ID C809C70A34D34D1
COUNTRY OF BEACON REGISTRATION 576/VANUATU
BEACON NUMBER ON AIRCRAFT OR VESSEL 0
HOMING SIGNAL 121.5
ACTIVATION TYPE AUTOMATIC OR MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 17 OCT 23 0637 UTC BY MEOSAR
ALERT LAST DETECTED AT 17 OCT 23 0637 UTC
DOA – 22 53.34 S  170 15.06 E  ESTIMATED ERROR UNKNOWN
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.035 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
Paragraph 4 indicates that this is a MEOSAR alert and provides the initial position. The
estimated error is shown as “UNKNOWN” because the reporting MEOLUT is not
commissioned to meet MEOSAR IOC requirements for DOA position accuracy and the
reliability of the estimated error.
2.
The MMSI for the vessel is formed by using the country code (576) and the beacon
information of 774000. The MMSI is therefore 576774000.

![Image 1 from page 83](/images/cospas-sarsat/G-series/G007/G007_page_83_img_1.png)

6–15

6.4.2
A Position Confirmed Alert using LEOSAR Data
A later LEOSAR detection provides further position information that is used to
confirm the position for the beacon with Hex ID: C809C70A34D34D1, as shown
below. See the description of “Confirmation” in section 4.1.3.
1.  DISTRESS COSPAS-SARSAT POSITION UPDATE ALERT
2.  MSG NO 05717 AUMCC REF C809C70A34D34D1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE USER - EPIRB USER
MMSI ALL 9 DIGITS 576774000
HEX ID C809C70A34D34D1
COUNTRY OF BEACON REGISTRATION 576/VANUATU
BEACON NUMBER ON AIRCRAFT OR VESSEL 0
HOMING SIGNAL 121.5
ACTIVATION TYPE AUTOMATIC OR MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 17 OCT 23 0647 UTC BY LEOSAR SARSAT 10
MCC REFERENCE - 22 53.34 S  170 15.06 E
DOPPLER A - 22 50.15 S  170 13.76 E
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0370 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
The MCC reference position is identical to the previously received DOA position as the
Doppler location matches the DOA position.
2.
The AUMCC has used the previous DOA location as the MCC reference position and
has not merged the DOA location with the matching Doppler location. Other MCCs may
merge the matching DOA and Doppler location to produce the MCC reference position
or use the Doppler location as the MCC reference position.

6–16

6.5
A Position Conflict Alert
The following example with an ELT with Hex ID 2DC753D464FFBFF shows an incident
where two positions generated do not match and a conflict alert is sent to the SAR Service.
The example is based on a real-world incident but amended for presentation. (The actual
format of SIT 185 messages sent by the USMCC differs somewhat from those shown in
these examples. Note that the USMCC sends national formatted messages to its national
SAR Services rather than SIT 185 messages.)
6.5.1
A GEOSAR GNSS Position Alert
The initial GEOSAR detection provides GNSS position information for the beacon
with Hex ID 2DC753D464FFBFF:
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 72554  USMCC REF 42321
3.  BEACON MESSAGE INFORMATION
BEACON TYPE STANDARD LOCATION PROTOCOL - ELT
AIRCRAFT 24-BIT ADDRESS A9EA32 ASSIGNED TO USA
HEX ID 2DC753D464FFBFF
COUNTRY OF BEACON REGISTRATION 366/USA
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5
ACTIVATION TYPE NIL
GNSS POSITION PROVIDED BY EXTERNAL DEVICE
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 28 APR 23 1702 UTC BY GEOSAR GOES 17
GNSS - 33 31.27 N  083 56.93 W
UPDATE TIME WITHIN 4 HOURS OF DETECTION TIME
5.  OTHER INFORMATION
LUT ID 5123
DETECTION FREQUENCY 406.0248 MHZ
GNSS POSITION UNCERTAINTY PLUS-MINUS 2 SECONDS OF
LATITUDE AND LONGITUDE
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
Paragraph 4 shows the detection was made by the GOES-17 geostationary satellite.
2.
Paragraph 4 provides the GNSS position detected by the GOES-17 satellite. The GNSS
position is within the USMCC service area.
3.
Paragraph 3 indicates that the GNSS position was provided by an external device and
no further updates to the GNSS position will be possible under normal activation.
4.
Paragraph 5 provides the uncertainty of the GNSS position.

6–17

5.
Some message fields are “NIL” in Paragraph 3.  Message fields containing “NIL” in
Paragraph 4 have been omitted.
6.
The "AIRCRAFT 24-BIT ADDRESS A9EA32" (in paragraph 3 of the message) is
equivalent to the bit sequence “101010011110101000110010”.  As noted in Figure 6.7
below, the ICAO 24-bit allocation for the USA is “1010”.  Since the first four bits of the
address match that value, paragraph 3 indicates that this address is assigned to the USA.
The remaining 20 bits are used to code the individual US aircraft
7.
SIT 185 messages sent by the USMCC contain a 5-digit alert site number associated
with the beacon activation (e.g., 42321) as the “USMCC REF” in Paragraph 2. This
number is unique to a beacon activation and if the same beacon is activated again at a
different time, the 5-digit alert site number will be different.
Figure 6.7: ICAO 24-bit Addressing

![Image 1 from page 86](/images/cospas-sarsat/G-series/G007/G007_page_86_img_1.png)

6–18

Figure 6.7 above, contains an extract from the ICAO document [Annex 10
Vol III] concerning 24-bit addressing.  The table shows that the allocation of
addresses uses the four-bit sequence 1010 to indicate a US aircraft.
Figure 6.8: GEOSAR GNSS Position Alert
In the Figure 6.8 above, the footprint of the GEOSAR satellite GOES-17 is shown
in yellow and the location of the GOES-17 is shown by the yellow diamond. The
location of the GNSS position provided in the beacon message is shown by the green
triangle in the USA.

![Image 1 from page 87](/images/cospas-sarsat/G-series/G007/G007_page_87_img_1.png)

6–19

6.5.2
A Position Conflict Alert from a LEOSAR Position
The alert in this example is a LEOSAR detection that has two Doppler locations and
a GNSS position. Since neither Doppler location matches the GNSS position, a
position conflict alert is generated.
1.  DISTRESS COSPAS-SARSAT POSITION CONFLICT ALERT
2.  MSG NO 72555  USMCC REF 42321
3.  BEACON MESSAGE INFORMATION
BEACON TYPE STANDARD LOCATION PROTOCOL – ELT
AIRCRAFT 24-BIT ADDRESS A9EA32 ASSIGNED TO USA
HEX ID 2DC753D464FFBFF
COUNTRY OF BEACON REGISTRATION 366/USA
HOMING SIGNAL 121.5
GNSS POSITION PROVIDED BY EXTERNAL DEVICE
4.  ALERT POSITION INFORMATION
DETECTED AT 28 APR 23 1702 UTC BY LEOSAR SARSAT 10
GNSS - 33 31.27 N  083 56.93 W
UPDATE TIME WITHIN 4 HOURS OF DETECTION TIME
DOPPLER A - 33 09.82 N  085 19.92 W PROB 56 PERCENT
DOPPLER B - 44 41.41 N  144 00.65 W PROB 44 PERCENT
5.  OTHER INFORMATION
RELIABILITY OF DOPPLER POSITION DATA - SUSPECT DUE TO TECHNICAL
PARAMETERS
POSITION CONFLICT BASED ON DISTANCE SEPARATION AT LEAST 20 KM
DETECTION FREQUENCY 406.0247 MHZ
GNSS POSITION UNCERTAINTY PLUS-MINUS 2 SECONDS OF LATITUDE AND
LONGITUDE
6. REMARKS NIL
END OF MESSAGE
Notes:
1.
The two Doppler positions shown in Paragraph 4 do not match the GNSS position. The
closer Doppler, the A position (33° 10’ N, 085° 19’ W) is some 285 kilometres from the
GNSS position (33° 31’ N, 083° 57’ W). As the positions do not match, a position
conflict alert is sent to the RCC.
2.
In Paragraph 5, the Doppler position has been assessed as suspect due to technical
parameters. The satellite pass geometry (Cross Track Angle 23.7 degrees) is such that
the Doppler locations were near the edge of the satellite footprint and were assessed as
suspect. See Figure 6.9. As the Doppler positions are suspect, the GNSS position is more
likely to be the real beacon position than the Doppler positions, but the matching of
position data from independent sources is required to determine the real position of the
beacon.

6–20

Figure 6.9: LEOSAR Position Conflict Alert
In the Figure 6.9 above, the footprint of LEOSAR satellite Sarsat-10 at the TCA is
shown in orange, the yellow line is the track (path) of the satellite. The two Doppler
locations generated for this beacon detection are shown on the map. A position
conflict alert is generated as neither Doppler location is within the matching distance
of 20 kilometres of the GNSS position.

![Image 1 from page 89](/images/cospas-sarsat/G-series/G007/G007_page_89_img_1.png)

6–21

6.6
A Notification of Country of Registration Alert
6.6.1
An NOCR Alert
An NOCR alert is sent by an MCC to the country of registration for a beacon located
inside the service area of the MCC. In this example, the beacon with the Hex ID
C809C70A34D34D1 which is a Vanuatu EPIRB has locations in the Brazilian
MCC’s service area. The Brazilian MCC would send the NOCR to the Vanuatu SAR
Service via the MCC Network.
1.  DISTRESS COSPAS-SARSAT NOTIFICATION OF COUNTRY OF BEACON
REGISTRATION ALERT
2.  MSG NO 05714 AUMCC REF C809C70A34D34D1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE USER - EPIRB USER
MMSI ALL 9 DIGITS 576774000
HEX ID C809C70A34D34D1
COUNTRY OF BEACON REGISTRATION 576/VANUATU
BEACON NUMBER ON AIRCRAFT OR VESSEL 0
HOMING SIGNAL 121.5
ACTIVATION TYPE AUTOMATIC OR MANUAL
4.  ALERT POSITION INFORMATION
DETECTED AT 17 MAY 23 0637 UTC BY LEOSAR SARSAT 10
DOPPLER A - 18 33.54 S  062 15.06 W PROB 60 PERCENT
DOPPLER B - 22 53.34 S  043 21.60 W PROB 40 PERCENT
5.  OTHER INFORMATION
LUT ID 7101 BRAZILIA, BRAZIL
DETECTION FREQUENCY 406.0370 MHZ
6. REMARKS NIL
END OF MESSAGE
Notes:
1.
A Notification of Country of Registration (NOCR) alert message is sent to the country
of beacon registration by an MCC that has an alert with a position inside its service area
when the MCC has no other location within the SAR region of the country of beacon
registration. The NOCR alert message is intended to alert the SAR Service responsible
for the country code when the SAR Service would not otherwise be sent a located alert
for the beacon.
2.
In the alert message above the Brazilian MCC (BRMCC), in whose service area the
beacon was located, transmitted a NOCR alert message to the Australian MCC
(AUMCC) via the USA MCC (USMCC) for forwarding to the Vanuatu authorities. As
Vanuatu is serviced by the Noumea RCC in New Caledonia, the AUMCC has forwarded
the NOCR alert to Noumea RCC for delivery to the Vanuatu SAR Service.
3.
A graphical representation of the NOCR alert message is provided in Figure 6.10.

6–22

Figure 6.10: Graphical Representation of the NOCR Alert Message
In the Figure 6.10 above, the yellow line is the track of LEOSAR satellite Sarsat-
10. The footprint of Sarsat-10 at the TCA is shown in orange. As the beacon has a
country of registration of Vanuatu and has location data in the Brazilian MCC
service area, the Brazilian MCC sends a NOCR via the MCC network. In this case,
the NOCR would be sent via the United Status MCC, the Australian MCC and the
New Caledonian SPOC to the Vanuatu SPOC.

![Image 1 from page 91](/images/cospas-sarsat/G-series/G007/G007_page_91_img_1.png)

6–23

6.7
An Unresolved Doppler Position Match Alert
6.7.1
A LEOSAR Unresolved Doppler Position Match Alert
An unresolved Doppler position match alert is sent when two independent LEOSAR
detections match both possible Doppler locations prior to position confirmation. In
this example, the first detection is not shown. The second detection generated the
unresolved Doppler position match alert.
1.  DISTRESS COSPAS-SARSAT UNRESOLVED DOPPLER POSITION MATCH ALERT
2.  MSG NO 55408  AUMCC REF CDC9D64D41934D1
3.  BEACON MESSAGE INFORMATION
BEACON TYPE USER LOCATION - EPIRB USER
MMSI ALL 9 DIGITS 622120320
HEX ID CDC9D64D41934D1
COUNTRY OF BEACON REGISTRATION 622/EGYPT
BEACON NUMBER ON AIRCRAFT OR VESSEL 0
HOMING SIGNAL 121.5
ACTIVATION TYPE AUTOMATIC OR MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 17 MAY 23 0900 UTC BY LEOSAR SARSAT 11
GNSS - NIL
MCC REFERENCE - NIL
DOA - NIL
DOPPLER A - 36 34.74 N  000 22.26 W  PROB 99 PERCENT
DOPPLER B - 31 03.12 N  026 24.30 E  PROB 01 PERCENT
5.  OTHER INFORMATION
WARNING: AMBIGUITY IS NOT RESOLVED
LUT ID 6011 CAPE TOWN, SOUTH AFRICA
DETECTION FREQUENCY 406.0368 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
When both pairs of Doppler positions meet the match criterion prior to ambiguity
resolution for different satellite passes on similar orbital paths as shown in Figure 6.11,
an unresolved Doppler position match alert will be generated. (Note that in previous
example from 2011, the match criterion was 50 kilometres. The match criterion has since
been changed to 20 kilometres, also, the figure below is not to scale.)
2.
For the example above the following two pairs of Doppler locations were received:
Satellite Sarsat-10
TCA 0704 UTC, 17 May 2023,
A.  36° 18.1’ N - 000° 01.4’ E
B.  31° 05.0’ N - 025° 55.1’ E
Satellite Sarsat-11
TCA 0900 UTC, 17 May 2023,
A.  36° 34.7’ N - 000° 22.3’ W
B. 31° 03.1’ N - 026° 24.3’ E

6–24

3.
Both the A pair and B pair locations from the two satellites were within 20 kilometres
and this is depicted in Figure 6.8. As a consequence, ambiguity in position cannot be
resolved and an unresolved Doppler position match alert is transmitted.
4.
As a consequence, a warning will be inserted in the alert message in Paragraph 5
indicating that ambiguity has not been resolved.
5.
Although ambiguity is unresolved (i.e., position is unconfirmed), the new “A” position
is likely the true position based on its probability (99 percent).
Figure 6.11: Unresolved Doppler Position Match
In the Figure 6.11 above, the red line is the track of LEOSAR satellite Sarsat-10. The purple line is
the track of LEOSAR satellite Sarsat-11. The two Doppler locations generated by the Sarsat-10 pass
are shown as the two red triangles. The two Doppler locations generated by the Sarsat-11 pass are
shown as the two purple triangles. As both sets of Doppler positions match, neither location is
confirmed.

![Image 1 from page 93](/images/cospas-sarsat/G-series/G007/G007_page_93_img_1.png)

6–25

6.8
ELT(DT) Alerts
An ELT(DT) alert is sent after an ELT(DT) has been activated: manually by the crew,
automatically by the beacon when a probable crash has been detected (G-switch), or
automatically by the avionics when an aeroplane is in a distress condition.
6.8.1
An FGB ELT(DT) Alert
The DOA Position Conflict Alert message below is sent because the distance between
the DOA position which was independently processed by the Cospas-Sarsat System
and the GNSS position which was processed by the GNSS receiver associated with
the FGB ELT(DT), is at least 20 km away.
1.  DISTRESS TRACKING COSPAS-SARSAT DOA POSITION CONFLICT ALERT
2.  MSG NO 21013 CMCC REF 1D1200F03BBFDFF
3.  BEACON MESSAGE INFORMATION
BEACON TYPE ELT DISTRESS TRACKING
AIRCRAFT 24 BIT ADDRESS 01E077 ASSIGNED TO G BRITAIN
AIRCRAFT OPERATOR DESIGNATOR MMB
HEX ID 1D1200F03BBFDFF
COUNTRY OF BEACON REGISTRATION 232/G BRITAIN
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY EXTERNAL DEVICE
4.  ALERT POSITION INFORMATION
DETECTED AT 04 AUG 23 101501 UTC BY MEOSAR
ALERT LAST DETECTED AT 04 AUG 23 101501 UTC
GNSS - 61 54.40 N 045 37.53 W
UPDATE TIME WITHIN 2 – 60 SECONDS OF DETECTION TIME
ALTITUDE OF GNSS LOCATION BETWEEN 1600 AND 2200 METRES
(BETWEEN 5200 AND 7200 FEET)
DOA - 62 00.1 N 046 06.2 W
5.  OTHER INFORMATION
GNSS POSITION UNCERTAINTY PLUS-MINUS 2 SECONDS OF LATITUDE
AND LONGITUDE
DETECTION FREQUENCY 406.0400 MHZ
POSITION CONFLICT BASED ON DISTANCE SEPARATION OF AT LEAST
20 KM
ELT(DT) POSITION DOES NOT REFERENCE ANY PREVIOUS POSITION
6.  REMARKS
THIS DISTRESS TRACKING MESSAGE IS BEING SENT TO APPROPRIATE
SAR AUTHORITIES
PROCESS THIS ALERT ACCORDING TO RELEVANT REQUIREMENTS
END OF MESSAGE

6–26

Notes:
1.
Paragraph 1: The beacon message type is “DISTRESS TRACKING”.
2.
Paragraph 2: The beacon type is “ELT”, and the beacon subtype is “DISTRESS
TRACKING” for ELT(DT). The beacon is an FGB, since the beacon type does not
indicate “SGB”.
3.
Paragraph 3 provides the ICAO 24-bit address and the aircraft flag decoded from this
ICAO 24-bit address,
4.
Paragraph 3 also provides the 3-Letter Designator (3LD) of the airline operator (as
encoded in the FGB ELT(DT) rotating field) from which the airline can be identified per
ICAO document DOC 8585,
5.
Paragraph 4: For an FGB ELT(DT), the altitude of the GNSS position is provided within
a predetermined range of altitude values, in metres (and feet),
6.
Paragraph 6: See section 5.6 above for more information about “relevant requirements”.

6–27

6.8.2
An SGB ELT(DT) Alert
The DOA Position Match Alert message below is sent because the distance between the DOA
position that was independently processed by the Cospas-Sarsat System computed by the
MEOLUT and the GNSS position that was processed by the GNSS receiver associated with
the SGB ELT(DT) is less than 20 km.
1.  DISTRESS TRACKING COSPAS-SARSAT DOA POSITION MATCH ALERT
2.  MSG NO 00192  AUMCC REF B274FA041FD4710
3.  BEACON MESSAGE INFORMATION
BEACON TYPE  SGB – ELT DISTRESS TRACKING
AIRCRAFT 24 BIT ADDRESS 7100CE ASSIGNED TO SAUDI ARABIA
AIRCRAFT OPERATOR DESIGNATOR SVA
TAC 16001 SERIAL NO 509
HEX ID B274FA041FD4 7100CEA3F00
COUNTRY OF BEACON REGISTRATION 403/SAUDI
ACTIVATION TYPE AUTOMATIC BY BEACON (G-SWITCH/PROBABLE CRASH)
4.  ALERT POSITION INFORMATION
DETECTED AT 03 MAY 23 085310 UTC BY MEOSAR
ALERT LAST DETECTED AT 03 MAY 23 085310 UTC
GNSS - 02 24.40 N  046 04.11 E
TIME OF GNSS POSITION UPDATE: 03 MAY 23 085308 UTC
TIME SINCE GNSS LOCATION GENERATED: 0 MINUTES
ALTITUDE OF GNSS LOCATION: 125 METRES (410 FEET)
DOA - 02 25.1 N  046 06.2 E  ESTIMATED ERROR 001NMS
5.  OTHER INFORMATION
BEACON CHARACTERISTICS PER TAC DATABASE PROVIDED IN A SEPARATE
MESSAGE
GNSS POSITION UNCERTAINTY PLUS-MINUS 10 METRES
ELAPSED TIME SINCE ACTIVATION: 0 HOURS
REMAINING BATTERY CAPACITY BETWEEN 75 AND 100 PERCENT
DETECTION FREQUENCY 406.05 MHZ
ELT(DT) POSITION DOES NOT REFERENCE ANY PREVIOUS POSITION
6.  REMARKS
THIS DISTRESS TRACKING MESSAGE IS BEING SENT TO APPROPRIATE
SAR AUTHORITIES.
PROCESS THIS ALERT ACCORDING TO RELEVANT REQUIREMENTS.
END OF MESSAGE

6–28

Notes:
1.
Paragraph 3: The beacon type is “SGB ELT”, and the beacon subtype is “DISTRESS
TRACKING”,
2.
Paragraph 3: The beacon has been activated by the G-switch, indicating a likely crash
of the airplane.
3.
Paragraph 4: Time since GNSS location is provided by the SGB.
4.
Paragraph 4: The altitude of the GNSS location is an accurate value provided in metres
(and feet).
5.
Paragraph 5: For all SGBs, uncertainty of GNSS position provided in the alert message
is approximately 10 metres.
6.
Paragraph 5: SGBs may provide their remaining battery capacity within a range of
percentage values.
7.
Paragraph 6: Because of the large frequency spectrum that characterize an SGB, the
value is set to “406.05 MHZ” for any SGB if no DOA position is provided, otherwise
it is set to the actual detected value.

6–29

6.9
Cancellation Alerts
A cancellation is sent to indicate that the activation event is no longer active (for example,
hereafter, the events generating the ELT(DT) automatic triggering have returned to normal
values). An activation can only be cancelled using the same means that triggered the activation
(i.e., by avionics or manually). This cancellation message is for an SGB ELT(DT);
cancellation messages may also be sent for FGB ELT(DT)s and for other types of SGBs.
Notes:
1. Paragraph 1: The beacon message type is “USER CANCELLATION ALERT”.
2. Paragraph 3: The beacon was previously activated by the avionics, and the condition that
prompted the activation has returned to normal. The beacon type indicates “SGB”, and a
corresponding 23 Hexadecimal ID is provided in “HEX ID” line.
3. Paragraph 5: The System has received at least three (3) cancellation messages from the
beacon within 110 seconds, with no intervening “non-cancellation message”, and the
message indicates “CANCELLATION CONFIRMED”.
1.  DISTRESS TRACKING COSPAS-SARSAT USER CANCELLATION ALERT
2.  MSG NO 00192 AUMCC REF B274FA041FD4710
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SGB – ELT DISTRESS TRACKING
AIRCRAFT 24 BIT ADDRESS 7100CE ASSIGNED TO SAUDI ARABIA
AIRCRAFT OPERATOR DESIGNATOR SVA
TAC 16001 SERIAL NO 509
HEX ID B274FA041FD4 7100CEA3F00
COUNTRY OF BEACON REGISTRATION 403/SAUDI
ACTIVATION TYPE AUTOMATIC BY EXTERNAL MEANS (AVIONICS)
4.  ALERT POSITION INFORMATION
DETECTED AT 03 MAY 24 085810 UTC BY MEOSAR
ALERT LAST DETECTED AT 03 MAY 24 085310 UTC
DOA – 02 25.1 N  046 06.2 E  ESTIMATED ERROR UNKNOWN
5.  OTHER INFORMATION
ELT(DT) POSITION DOES NOT REFERENCE ANY PREVIOUS POSITION
CANCELLATION CONFIRMED
BEACON CHARACTERISTICS PER TAC DATABASE PROVIDED
IN A SEPARATE MESSAGE
REMAINING BATTERY CAPACITY BETWEEN 75 AND 100 PERCENT
DETECTION FREQUENCY 406.0510 MHZ
6.  REMARKS
THIS DISTRESS TRACKING MESSAGE IS BEING SENT TO APPROPRIATE
SAR AUTHORITIES
PROCESS THIS ALERT ACCORDING TO RELEVANT REQUIREMENTS
END OF MESSAGE

6–30

6.10 Sample SIT 985 Message with SGB Characteristics Based on TAC Number
In the following sample, the reference (REF) is provided as a 15 HEX ID and a 5-digit alert
site number.  The associated MCC sends a single SIT 985 message to a Distress authority to
accompany the first SIT 185 alert message sent to the Distress authority for the SGB
activation, as available, based on the TAC number encoded in the beacon message.
1.  BEACON OPERATIONAL CHARACTERISTICS
2.  MSG NO 00192 AUMCC REF ADD481135B60000 - 21348
3.  HEX ID ADD481135B60 00000000000
4.  CHARACTERISTICS FOR TAC 12345
– MANUFACTURER: APPLIED TECHNOLOGY CORP.
- BEACON MODEL: XXXYYY-01234
- BEACON TYPE: PLB
- BEACON SUBTYPE: FLOAT-FREE
- TEMPERATURE RANGE: -40C +55C
- HOMING: 121.5=5 MW - 406=25 MW - AIS=20 MW
- NAV DEVICE: GALILEO, GLONASS
- STROBE: BRIGHTNESS=0.75 CANDELA, DUTY-CYCLE=15 FLASH/MINUTE
END OF MESSAGE

6–31

6.11
A Ship Security Alert
SSAS (Ship Security Alert System) beacons are processed in the same manner as EPIRBs,
ELTs and PLBs, except that the SIT 185 message is not sent to the SAR Service associated
with the beacon location; instead, the SIT 185 message is sent to the Competent Authority in
the country of registration. Typically, the Competent Authority has a security focus rather than
the rescue focus of a SAR Service.
In the following example of a ship security alert, the beacon is first detected as an unlocated
initial alert and then as an initial located alert with two Doppler locations.
6.11.1 An Unlocated Ship Security Alert
1.  SHIP SECURITY COSPAS-SARSAT INITIAL ALERT(UNLOCATED)
2.  MSG NO 00285  AUMCC REF 401917C900FFBFF
3.  BEACON MESSAGE INFORMATION
BEACON TYPE STANDARD LOCATION - SHIP SECURITY
MMSI ALL 9 DIGITS 512573000
HEX ID 401917C900FFBFF
COUNTRY OF BEACON REGISTRATION 512/NEWZEALAND
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY EXTERNAL DEVICE
4.  ALERT POSITION INFORMATION
DETECTED AT 07 JAN 23 2020 UTC BY GEOSAR GOES 17
5.  OTHER INFORMATION
LUT ID 5123
DETECTION FREQUENCY 406.0278 MHZ
6.  REMARKS
THIS IS A SHIP SECURITY ALERT.
PROCESS THIS ALERT ACCORDING TO RELEVANT SECURITY REQUIREMENTS.
END OF MESSAGE
Notes:
1.
This is an example of a ship security alert transmitted to a competent authority. MCCs
would transmit this alert to the AUMCC for forwarding to the New Zealand relevant
authority irrespective of the location of the alert.
2.
The activation type provided in Paragraph 3 will always indicate “MANUAL” for an
SSAS beacon, which can only be activated manually.
3.
The graphics depiction of this alert is provided in Figure 6.12.

6–32

6.11.2 A Ship Security Initial Alert with Positions
An initial located alert is generated for the same beacon with two Doppler locations.
1.  SHIP SECURITY COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 00286  AUMCC REF 401917C900FFBFF
3.  BEACON MESSAGE INFORMATION
BEACON TYPE STANDARD LOCATION - SHIP SECURITY
MMSI ALL 9 DIGITS 512573000
HEX ID 401917C900FFBFF
COUNTRY OF BEACON REGISTRATION 512/NEWZEALAND
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY EXTERNAL DEVICE
4.  ALERT POSITION INFORMATION
DETECTED AT 07 JAN 23 2023 UTC BY LEOSAR SARSAT 13
DOPPLER A - 29 05 N  090 18 W  PROB 76 PERCENT
DOPPLER B - 40 13 N  039 02 W  PROB 24 PERCENT
5.  OTHER INFORMATION
THE B POSITION IS LIKELY TO BE AN IMAGE POSITION
DETECTION FREQUENCY 406.0278 MHZ
6.  REMARKS THIS IS A SHIP SECURITY ALERT.
PROCESS THIS ALERT ACCORDING TO RELEVANT SECURITY REQUIREMENTS.
END OF MESSAGE
Notes:
1.
A second alert was received for this beacon incident. A ship security alert is processed
like any other beacon incident except that the SIT 185 message is sent to the Competent
Authority for the country of registration.
2.
This ship security beacon has the capability to provide a GNSS position (as it is coded
with a Location protocol) but in this case, no GNSS position was transmitted in the
beacon message received by the LEOLUT.
3.
Doppler position B with 24% probability has been further identified as being the likely
image position given the initial GEOSAR detection. See the graphics in Figure 6.12.

6–33

Figure 6.12: Ship Security Unlocated and Initial Alert
In the Figure 6.12 above, the orange line indicates the track of LEOSAR satellite
Sarsat-13. The orange area is the footprint of Sarsat-13 at the TCA for the beacon.
The GOES-17 footprint is indicated by the yellow line. The section of the Sarsat-13
footprint that overlaps with the GOES-17 footprint is shaded in light grey. The
Doppler B location generated by the Sarsat-13 pass is outside the GOES-17
footprint, and hence, is reported as likely to be the image position.

![Image 1 from page 102](/images/cospas-sarsat/G-series/G007/G007_page_102_img_1.png)

6–34

6.12
An Alert with an Invalid Beacon Message
A beacon message is invalid when a LUT is unable to correct errors in the beacon message or
the MCC detects an invalid value associated with the beacon message. All the fields in an
invalid beacon message are omitted or reported as “NIL” in the SIT 185 message, except for
the Hex ID which (even though it is reported) may also be invalid. Any DOA or Doppler
location data is valid and is reported in the SIT 185 message.
6.12.1
An Alert with an Invalid Beacon Message
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 79416  AUMCC REF 7722B4600017491
3.  BEACON MESSAGE INFORMATION
DATA DECODED FROM THE BEACON MESSAGE IS NOT RELIABLE
HEX ID 7722B4600017491
4.  ALERT POSITION INFORMATION
DETECTED AT 09 JUN 23 0701 UTC BY LEOSAR COSPAS 14
DOPPLER A - 18 36.66 S  146 11.05 E  PROB 66 PERCENT
DOPPLER B - 13 02.22 S  171 15.38 E  PROB 34 PERCENT
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0367 MHZ
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
Despite the error detection and correction capability of the system, the LUT was not able
to correct all errors in the beacon message received for this particular detection. As a
consequence, Paragraph 3 indicates that the decoded data is not reliable and the various
beacon message fields are omitted because they are not reliable.
2.
Note that the Hex ID of the beacon “7722B4600017491” decodes as an orbitography
beacon with an invalid country code which suggests the Hex ID is invalid and should be
treated with caution by an RCC. The Hex ID for every invalid beacon message should
be treated with caution, since the invalid information may not be evident from the
decoded Hex ID.
3.
The invalid beacon message does not imply that the Doppler location is invalid as the
Doppler location is generated from the beacon transmission, not the contents of the
beacon message. The Doppler location in alerts with an invalid beacon message has been
used to rescue persons in distress.
6.13
An Alert with a Satellite Manoeuvre Warning
The Cospas-Sarsat LEOSAR satellites sometimes have to undergo a manoeuvre to adjust the
orbit of the satellite. After the satellite orbit has changed, LEOLUTs may have inaccurate orbit
information for the satellite and may generate a position that is outside normal accuracy. A
warning is included in SIT 185 messages for 24 hours after a satellite manoeuvre when the
expected error for Doppler positions computed with data from a manoeuvred satellite may
exceed ten (10) kilometres.

6–35

6.13.1 An Initial Alert (with a Satellite Manoeuvre Warning)
An
initial
alert
has
been
generated
for
the
beacon
with
Hex
ID
“BEEE43A58C0022D” but the satellite used to determine the position has recently
undergone a manoeuvre for which the maximum expected impact in Doppler location
accuracy has exceeded ten (10) kilometres within 24 hours of this manoeuvre.
1.  DISTRESS COSPAS-SARSAT INITIAL LOCATED ALERT
2.  MSG NO 76380  AUMCC REF BEEE43A58C0022D
3.  BEACON MESSAGE INFORMATION
BEACON TYPE SERIAL USER LOCATION - EPIRB (NON FLOAT FREE)
SERIAL NO 0059747
HEX ID BEEE43A58C0022D
COUNTRY OF BEACON REGISTRATION 503/AUSTRALIA
BEACON NUMBER ON AIRCRAFT OR VESSEL NIL
HOMING SIGNAL 121.5 MHZ
ACTIVATION TYPE MANUAL
GNSS POSITION PROVIDED BY NIL
EMERGENCY CODE NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 14 JAN 23 2310 UTC BY LEOSAR SARSAT 11
GNSS - NIL
MCC REFERENCE – NIL
DOPPLER A - 39 15.04 S  151 15.77 E  PROB 54 PERCENT
DOPPLER B - 37 56.05 S  144 36.48 E  PROB 46 PERCENT
5.  OTHER INFORMATION
RELIABILITY OF DOPPLER POSITION DATA SUSPECT DUE TO
SATELLITE MANOEUVRE
DETECTION FREQUENCY 406.0280 MHZ
TAC 0139
BEACON MODEL - STANDARD COMMS, AUSTRALIA MT400
6.  REMARKS NIL
END OF MESSAGE
Notes:
1.
This alert was generated within 24 hours of a manoeuvre of the Sarsat-11
satellite and contains a related warning in Paragraph 5.

6–36

6.14
An Interferer Alert
An interferer is a signal transmitting between 406.0 to 406.1 MHz that does not have the
correct signal structure for a Cospas-Sarsat distress beacon. Interferers with a location are
reported to the appropriate spectrum authority. While there is no defined SIT 185 message
format for reporting interferer alerts, the sample message below is provided per national
procedure.
6.14.1 An Initial Interferer Alert
1.  DISTRESS COSPAS-SARSAT 406 MHZ INTERFERER ALERT
2.  MSG NO 37533 THMCC REF 88047/88048
3.  BEACON MESSAGE INFORMATION
HEX ID NIL
4.  ALERT POSITION INFORMATION
DETECTED AT 16 MAY 23 0311 UTC BY LEOSAR SARSAT 13
DOPPLER A - 17 40 N  096 11 E PROB 50 PERCENT
DOPPLER B - 16 59 N  099 34 E PROB 50 PERCENT
5.  OTHER INFORMATION
DETECTION FREQUENCY 406.0170 MHZ
6.  REMARKS
PLEASE ADVISE YOUR SPECTRUM AGENCY OF ANY PERSISTENT INTERFERER
END OF MESSAGE
Note:
1.
An interferer does not have a Hex ID, so no Hex ID is provided in Paragraph 3.
An interferer reference number is provided in Paragraph 2.
2.
The comments in Paragraph 6 request that the spectrum agency be advised of
persistent interferers.

6–37

Figure 6.13: 406-MHz Interferer Alert
In the Figure 6.13 above, the yellow line marks the track of LEOSAR satellite Sarsat-
13. The footprint for Sarsat-13 at the TCA for the interferer detection is shown by the
orange outline. The two Doppler locations for the interferer are shown.
- END OF SECTION 6 –

![Image 1 from page 106](/images/cospas-sarsat/G-series/G007/G007_page_106_img_1.png)

7–1

FREQUENTLY ASKED QUESTIONS
7.1
What is the difference between an RCC and a SPOC?
Answer: An RCC is a Rescue Coordination Centre and provides a SAR response
within a declared SAR region designated by IMO and ICAO. Cospas-Sarsat uses the
term SPOC (SAR Point of Contact) as a generic term to refer to the SAR agencies
sent SIT 185 alerts by an MCC. Many but not all SPOCs are RCCs. The list of SPOCs
with their contact details is available on the Cospas-Sarsat website.
7.2
What Cospas-Sarsat training is available for Distress authority personnel?
Answer: Cospas-Sarsat document C/S P.015 includes a description of a model
Cospas-Sarsat training course for SAR Service personnel.
7.3
My Distress authority needs to discuss the contents of a Cospas-Sarsat distress
alert with an MCC. Where can it find contact information for the MCC?
Answer: The contact information for MCCs is provided on the Cospas-Sarsat website
(www.cospas-sarsat.int).
7.4
My Distress authority has a question on a particular aspect of the Cospas-Sarsat
system and is unable to find the answer in the Handbook. Who should the
Distress authority contact to discuss the matter?
Answer: The Distress authority should contact its supporting MCC in the first
instance for assistance. To establish your supporting MCC check Annex C and then
the Cospas-Sarsat website (www.cospas-sarsat.int) for the MCC contact details.
7.5
What is the Hex ID? Why does a Distress authority need to know this Hex ID
when the serial identity of the beacon is provided in Paragraph 3 in a manner
that can be clearly understood by Distress authority personnel?
Answer: See section 2.4 for an explanation of Hex ID. MCCs worldwide use this Hex
ID in the main to refer to a beacon and to undertake searches for specific beacon
activations in their system. It should be noted that the Hex ID is unique and no two
identical Hex IDs should exist on two different beacons. Furthermore, most 406 MHz
beacon registration databases use the Hex ID as the primary field. Distress authority
personnel will facilitate discussions with MCCs on distress alerts if reference is made
to the Hex ID. The serial identity provided for some beacon protocols in Paragraph 3
of the alert message received by the Distress authority is decoded from the Hex ID
and provides information in respect of the beacon coding protocol used, the beacon
type and the specific identity of the source or carrier, such as the Callsign.
7.6
How can I decode the 15 character Hex ID?
Answer: There are several stand-alone programs available for this purpose. The
Cospas-Sarsat website provides an online capability.

7–2

7.7
Why has the Distress authority received a MEOSAR alert but not a LEOSAR
alert for a beacon? Why does the LEOSAR system sometimes detect a beacon
but not the MEOSAR system?
Answer: The system may provide a MEOSAR detection but not a LEOSAR detection
if there is no LEOSAR satellite that has passed over the beacon. The LEOSAR
satellites do not continuously cover the surface of the earth, but each LEOSAR
satellite covers the earth in approximately 12 hours. Alternatively, a LEOSAR
satellite may have passed over the beacon, but the beacon transmission may have
been shielded from the LEOSAR satellite, such as when the beacon is in a
mountainous region, a canyon or gorge.
The LEOSAR satellites have a lower altitude orbit (between 700 and 1000
kilometres) so are able to detect weaker signals than the MEOSAR satellites which
have an altitude of 19,000 to 24,000 kilometres. The weaker signal may be due to a
damaged beacon or shielding if the beacon is activated indoors for example.
7.8
The Distress authority has received multiple CONFLICT alerts for the same
LEOSAR beacon event, i.e., same satellite, same beacon Hex ID and same TCA
(± 20 minutes). Why is this?
Answer: In all probability, the alerts are from different LEOLUTs, albeit the same
beacon event. Different LEOLUTs may generate different Doppler locations because
different beacon bursts were available from the satellite due to the different LEOLUT
locations, detection capability or time of acquisition. Different processing algorithms
or orbital configuration data could result in different Doppler locations, even when
two LEOLUTs use the same beacon bursts. A subsequent Doppler position conflict
alert for the same beacon event is transmitted unless the new alert is determined to be
of poorer quality.
7.9
The TCA in the LEOSAR distress alert just received is some four (4) hours old.
Why is this?
Answer: This happens when a LEOLUT tracks a particular satellite which it had not
tracked for many hours and receives the recorded detection from an earlier orbit. It is
assumed that the beacon had not been detected on subsequent passes by that particular
satellite.
7.10
Position update alerts are being received multiple times after position
confirmation, but the MCC reference position provided is changing. Why is
this? Furthermore, why is the GNSS position remaining constant during this
exchange?
Answer: In some MCCs, an MCC reference position is calculated based on the most
current location data and the historical locations that meet the distance matching
criterion. The MCC reference position may be biased to the location with the smaller
likely error. No two locations will be identical even when the same data from a
satellite is used for processing. The GNSS position will remain constant if it was
received from an external source that is not providing updates, if the beacon is not

7–3

designed to provide updates (likely an older beacon model), or if a Location Protocol
FGB’s location has not changed by at least four (4) seconds of latitude and longitude.
(Since its component longitude and latitude are each rounded to the nearest four (4)
seconds, a Location Protocol FGB’s position could change by nearly six (6) seconds
without a change in the GNSS position; i.e., Square Root of (4\*4 + 4\*4) = 5.66.)
7.11
Paragraph 5 of a Cospas-Sarsat distress alert reports that the Doppler A
position is probably the image location, and it has a probability of 79%. Does
this mean that B position is confirmed? Furthermore, why is the A position with
a higher probability considered the image position? Is there a problem with the
location processing?
Answer: The determination that one position is probably an image does not indicate
that the other position is confirmed; confirmation of a Doppler location only occurs
by matching it with independent locations. On occasion, the Doppler location with
the lesser probability is in fact the real position of the distress, so this should not be
construed as an anomaly. The reference to “image position” is made when one
position in a Doppler solution is within the footprint of another satellite that detected
the beacon, and the other Doppler position is not within the satellite footprint.
7.12
The SAR Service has received a 406 MHz interferer alert. What should the RCC
do with this information?
Answer: Persistent 406 MHz interferer transmissions negatively impact the
Cospas-Sarsat system and should be turned off. They should be reported to the
national spectrum agency, who may deal with them directly (for internal sources) or
report them to the ITU (for foreign sources). More information on 406 MHz
interference is provided in the Cospas-Sarsat document C/S A.003, “Cospas-Sarsat
System Monitoring and Reporting”.
7.13
What does it mean when the alert states that the GNSS position update time is
within four (4) hours of detection time? Why isn’t a precise time provided?
Answer: Unfortunately, the time associated with the GNSS position is not part of the
beacon transmission as there are not enough data bits available to transmit the time.
The alert states that the location was updated within four (4) hours of the detection
time because the 406 MHz Beacon Specification (C/S T.001) requires that GNSS
position not be transmitted if it has not been updated within four (4) hours.
An alert indicating an “internal” source for the GNSS position is likely within a few
minutes of the detection time (although the beacon is not required to update its GNSS
position). In addition, when the GNSS position changes on a subsequent alert, the
update time of the GNSS position is between the two reported detection times.

7–4

7.14
The alert provides 6 Hex characters for an ELT 24-bit address. What is the 24-
bit address and how is it useful to a SAR Service? Is there a database that lists
all these six (6) Hex characters?
Answer: The aircraft 24-bit address is used in applications which require the routing
of information to or from individual, suitably equipped aircraft. Examples of this are
the aeronautical fixed telecommunication network (AFTN), SSR Mode S, and the
airborne collision avoidance system (ACAS). The 24-bit address transmitted by an
ELT is expressed as six hexadecimal characters in the distress alert and can be used
to identify the precise aircraft provided an appropriate database is maintained. The
24-bit address can also identify the country that assigned it, and thus assist an RCC
in its fact-finding efforts. The allocation of 24-bit aircraft addresses, formerly known
as Mode S addresses, is described in the ICAO convention, Chapter 9 of Annex 10,
Volume III. Alternatively, contact your State-aircraft-registration authority.
7.15
How is it useful for the Distress authority to be notified that the GNSS position
was provided by an external device? Is it useful for the Distress authority to
know that the activation type is “NIL”?
Answer: The advice that the GNSS position is provided by an external device
indicates that the beacon does not have an integral GNSS which can provide updated
positions as long as the beacon remains active. An external input from a ship’s or
aircraft’s GNSS (or other navigation system) will indicate that the GNSS position is
unlikely to be updated after initial activation (as the beacon is usually separated from
the external input).
The activation type is only available with the user protocol and not supported in any
of the location protocols. A manual activation type indicates that the beacon was
activated by a survivor. A manual or automatic activation type indicator is probably
not useful.
7.16
Paragraph 3 of the Cospas-Sarsat distress alert provides information on
“beacon number on aircraft or vessel”. What is the significance of this
information? Why does this Paragraph often indicate “NIL” or “0” (zero)?
Answer: Certain beacon coding protocols, e.g., Maritime User and Radio Callsign
User protocols, allow multiple beacons to be coded with the same callsign or MMSI.
In order to differentiate between these beacons on board the same vessel and to
provide a unique Hex ID, the beacon is coded with a specific beacon number, 0 to 9
and A to Z. If the vessel carries only one such coded beacon, then the specific number
will be zero. Receiving a distress alert with the specific beacon number given as, say
1, indicates that there are additional beacons on board the vessel.
7.17
The Distress authority has received an alert for the first time for a beacon
indicating a position conflict alert. How is this possible when the Distress
authority did not receive a prior alert?
Answer: For non-SSAS alerts, the initial alert might have been transmitted to another
SAR Service because the initial location or locations were in that SAR Service’s

7–5

SRR. The subsequent alert, which is in conflict, contains positions in the subject SAR
Service’s SRR.
Alternatively, the position conflict alert sent to the Distress authority may contain a
GNSS position that does not match either the DOA or Doppler location in the alert.
7.18
The Distress authority has reported that it has received message number 00533
from its support MCC as per Paragraph 2 of the distress alert message.
However, the previous message number received was 00530. The Distress
authority wishes to account for all messages and requests an explanation.
Answer: A communication problem could cause messages to be missed. The Distress
authority should request the support MCC to retransmit any missing messages.
7.19
Why does the MCC send regular communication checks to my SAR Service?
Should I respond to the communication check?
Answer: The IMO and ICAO have noted that there are known and documented
problems in regard to SAR Services initiating SAR action in response to Cospas-
Sarsat distress alerts. It was further noted that there were cases where the Cospas-
Sarsat System successfully delivered distress alerts but the SAR Service did not
respond. It was recognised that the fault lay in the SAR response system and not with
the delivery of alerts by Cospas-Sarsat MCCs.
For this reason, IMO and ICAO have requested that Cospas-Sarsat MCCs undertake
regular communication checks with the SAR Services they support.
SAR Services should respond promptly to the MCC when they receive a
communication check.
7.20
Are there examples of how independence is determined when matching
locations?
Answer: Here are some examples of how an MCC determines if two locations can be
used to determine a matching location:
A GNSS position from a MEOLUT and a GNSS position from a LEOLUT can not
confirm location, even if the two GNSS positions are the same, as the two GNSS
positions come from the same source (the beacon) and can never be assumed to be
independent.
A Doppler location and a GNSS position confirm a location if the two locations match
(i.e., are within 20 kilometres of each other) as a Doppler location and a GNSS
position are independent of each other.
Data from LEOSAR satellite Sarsat-10 gives two Doppler locations (L1 and L2) and
DOA data from a MEOLUT gives location L3. If L1 and L3 match, then the MCC
will provide an MCC reference position derived from L1 and L3.
A Doppler location generated by satellite Sarsat-12 from one LEOLUT and a Doppler
location generated by satellite Sarsat-12 with the same TCA from a different

7–6

LEOLUT would not confirm the location as the Doppler locations are from the same
beacon event.
Data from LEOSAR satellite Sarsat-12 gives two Doppler locations (L1 and L2) and
data from LEOSAR satellite Sarsat-12 gives two Doppler locations (L3 and L4). If
the second pair of locations have a different TCA (i.e., are from a different satellite
pass) and only L1 and L3 match, then the location is confirmed. The MCC will
provide an MCC reference position derived from L1 and L3.
Data from LEOSAR satellite Sarsat-10 gives two Doppler locations (L1 and L2) and
data from LEOSAR satellite Sarsat-12 gives two Doppler locations (L3 and L4), and
there are two matches, both L1 and L3, as well as L2 and L4. This situation is known
as an Unresolved Doppler Match and the second pair of Doppler locations does not
confirm a location.
A DOA location with three satellites (X1, X2, X3) with time T1 and a DOA location
with four satellites (X2, X3, X6, X7) with time T2. If the two locations match, then
if the times are not within two (2) seconds and as each satellite set has a unique
satellite combination (X1 is not in the second set and X6 is not in the first set), the
location is confirmed.
A DOA location with three satellites (X1, X2, X3) with time T1 and a DOA location
with four satellites (X1, X2, X3, X4) with time T2. If the times are within 30 minutes,
then as the satellite sets are not different (the first set of satellites is contained in the
second set) the location is not confirmed, even if the two locations match. If two DOA
locations match and the data times for the two alerts differ by at least 30 minutes,
then the location is confirmed, regardless of the sets of satellites.
Data from a LEOLUT gives two Doppler locations: the A-position has a probability
of 97% and the B-location has a probability of 3%. Despite the strong indication that
the A-position is the real location of the beacon, the location is not confirmed as in
some cases the location of the beacon will be the B-position.
An MCC may be able to use footprint information to indicate which of two Doppler
locations is likely to be the image location (i.e., the location that is not the location of
the beacon). For example, if a beacon is detected by a GEOSAR satellite and there
are two Doppler locations from a LEOSAR detection, and if one location is outside
the footprint of the GEOSAR satellite, then it is likely that this is the image location.
Despite this information, footprint determination is not used to confirm a location.
See section 6.2 for an example of this processing.
7.21
How is the nine-digit MMSI formed using the six digits provided in a SIT 185?
Answer: For beacons coded with an MMSI protocol, Paragraph 3 of the SIT 185
provides the last six digits of the Maritime Mobile Service Identity (MMSI). The
nine-digit MMSI is formed by adding the six digits to the country code provided in
the country of registration field.
Note that some countries have more than one country code (known as the Maritime
Identification Digits (MID)). For example, Panama has seven country codes, so there
could be seven nine-digit MMSIs with the same last six digits provided in Paragraph

7–7

3. If the beacon has not been correctly coded with correct MID, then the resulting
nine-digit MMSI will not be correct.
Similarly, it is possible that a beacon with a particular MMSI is transferred to a
different vessel without the beacon being re-programmed with the MMSI of the new
vessel. Incidents have occurred where a beacon with an MMSI has been activated
that does not match the MMSI of the vessel in distress.
7.22
Why does a beacon take 50 seconds to transmit its first burst once activated?
Answer: Except for ELT(DT)s, Cospas-Sarsat FGBs are designed to have a 50-
second warm-up time to allow the oscillator frequency to stabilize before the beacon
begins transmitting. For the LEOSAR system, an unstable oscillator frequency would
probably generate an inaccurate location estimate.
Cospas-Sarsat FGB ELT(DT)s and SGBs require transmission of the first burst
shortly after beacon activation.
7.23
What is the difference between a coarse GNSS position and a refined GNSS
position?
Answer: The data transmitted in the message from a distress beacon includes error-
correcting codes that allow a LUT to fix some errors in the data. The data from an
FGB has two components known as PDF-1 (Protected Data Field 1) and PDF-2
(Protected Data Field 2). An FGB message may have a valid PDF-1 but an invalid
PDF-2 that cannot be corrected by the error-correcting codes.
An FGB message with a valid PDF-1 that contains GNSS position, and an invalid
PDF-2 will provide a coarse GNSS position. The coarse GNSS position is less
accurate than the refined GNSS position that is provided when both data fields are
valid.
For example, consider an FGB with a National Location protocol with the GNSS
position (33 23.73 S, 150 19.60 E). The GNSS position is contained in the beacon
message as a coarse GNSS position (33 24.00 S, 150 18.00 E) with an adjustment of
-0.27 minute latitude and +1.6 minute longitude. The coarse location is contained in
the PDF-1 field and the fine adjustment is contained in the PDF-2 field. If the PDF-1
field is valid but the PDF-2 field is invalid (as it has too many errors), the GNSS
position will be reported in the SIT 185 message as (33 24.00 S, 150 18.00 E). If the
LUT detects a later transmission that has valid PDF-1 and PDF-2 fields, then the
refined GNSS position of (33 23.73 S, 150 19.60 E) will be sent to the MCC.
SGB messages only contain a single error-correcting code and the precision of a
GNSS position is always the same for an SGB (i.e., approximately 10 metres).
The alert message sent from an MCC to a Distress authority indicates the precision
for a GNSS position.
7.24
Could the following confusing incident be explained? The New Zealand RCC
received an initial alert for beacon 400E70784B59A9F with two Doppler
locations and no GNSS position and later received a position confirmed alert for

7–8

beacon 400E70784AFFBFF containing a Doppler location and a GNSS position
that matched, and an MCC reference position. The MCC reference position was
near one of the Doppler locations in the initial alert. Were two beacons active?
If it was the same beacon, why were the Hex IDs different (but similar) and why
did the first detection not have a GNSS position?
Answer: There was only one beacon in this incident. The initial alert contained a
warning in Paragraph 3 that the data decoded from the beacon message was not
reliable. For this reason, the GNSS position, which is part of the beacon message,
was suppressed and not included in the first SIT 185 message sent to the New Zealand
RCC.
When a LUT receives a beacon message, it performs processing on the data to
produce the Hex ID. As the first beacon message was invalid, the LEOLUT did not
perform the processing on the Hex ID and this is why it is different (but similar) to
the Hex ID in the position confirmed alert. Any Hex ID associated with a SIT 185
with a warning that the data is not reliable should be treated with caution by a Distress
authority. Although the data in a beacon message may be invalid, the Doppler or
DOA locations in such a message are valid, as demonstrated in this incident, as one
of the Doppler locations in the initial alert was very near the actual location of the
beacon.
7.25
Where can a SAR Service get more information about the Return Link Service
function in the MEOSAR system?
Answer: The Return Link Service (RLS) is described in a video available at
https://www.cospas-sarsat.int/en/search-and-rescue/programme-videos-en. A SAR
Service should contact its supporting MCC to obtain more information about the
RLS.
7.26
What is the difference between an LG MCC and an LGM MCC?
Answer: An LG MCC is an MCC that is only capable of processing LEOSAR and
GEOSAR data. An LGM MCC is an MCC that is capable of processing LEOSAR,
GEOSAR and MEOSAR data.
MEOSAR is the most recent satellite system added to the Cospas-Sarsat system.
Before the introduction of MEOSAR, all MCCs were LG MCCs. An LG MCC must
be upgraded and commissioned in order to become an LGM MCC.
7.27
Why does my Distress authority receive multiple DOA position update alerts
with the same detection time (as reported in Paragraph 3 of the SIT 185
message)?
Answer: This could occur for two reasons:
1)  The new alert contains a DOA position with better expected accuracy, as indicated
in Paragraph 4.

7–9

2) While the new alert contains the same first detection time (per Paragraph 4), the
new alert contains new detection data, as indicated by the last detection time reported
in the subsequent data line. Except for ELT(DT)s, an updated DOA position alert is
sent if the new alert contains data that is newer than data in all previous alerts, by at
least five (5) minutes before position confirmation and at least 15 minutes after
position confirmation.
7.28
What is an ELT(DT)?
Answer: An ELT(DT) is a distress tracking ELT, which is Cospas-Sarsat’s version
of an Autonomous Distress Tracking device to comply with the requirements of
ICAO Annex 6.  It is used to provide information about the location of an aircraft that
is in a potential distress situation. An ELT(DT) may be activated when an aircraft’s
avionics instrumentation has determined that the flight characteristics are sufficiently
abnormal that the aircraft is in imminent danger of an accident. An ELT(DT) may
also be activated manually by the crew or automatically due to the G-switch (probable
crash), like other ELTs.
7.29
Is an ELT(DT) like other ELTs?
Answer: Conceptually, an ELT(DT) is only required to meet ICAO Annex 6
requirements for Autonomous Distress Tracking devices.  However, the Cospas-
Sarsat Beacon Performance Specifications (documents C/S T.001 and C/S T.018)
include provisions to ensure that an ELT(DT) will be designed to meet the same
standard requirements as an ELT(AF), ELT(AP) or ELT(AD), for capabilities such
as:
•
automatic G-switch activation,
•
beacon transmit frequency,
•
beacon message structure,
However, ELT(DT)s transmit very frequently soon after activation (i.e., every 5
seconds within the first 120 seconds), to help ensure that an accurate location is
provided in the event of an imminent crash. Unlike other ELT(s), ELT(DT)s may be
activated automatically while in flight due to the aircraft avionics detecting abnormal
flight characteristics. While other ELTs are required to have a 24-hour battery
capacity, an ELT(DT) is only required to have a 370-minute battery capacity, unless
it is crash-survivable.
7.30
If the aircraft is still in flight, why is this ELT(DT) alert message sent to the
Distress authority?
Answer: ELT(DT)s transmit automatically when the aircraft’s avionics detects
anomalous conditions indicating that the aircraft is in imminent danger of crashing.
In the first 120 seconds after activation, an ELT(DT) transmits every five (5) seconds
so that its location can be accurately determined in the event of a crash. Once an
aircraft crashes, its ELT(DT) (or other emergency equipment) may be unable to
transmit properly.  In short, ELT(DT) alerts are sent to Distress authorities so that

7–10

these authorities can respond properly to an aircraft that is in imminent danger of
crashing.
In addition, nodal MCCs automatically send ELT(DT) incident alert data to the
Location of Aircraft in Distress Repository (LADR), which is operated for ICAO as
a part of the Global Aeronautical Distress and Safety System.
- END OF SECTION 7 –

A-1

ANNEX A
ACRONYMS AND TERMINOLOGY
ACRONYM
TERMINOLOGY
ACAS
Airborne Collision Avoidance System
ADT
Autonomous Distress Tracking
AFTN
Aeronautical Fixed Telecommunication Network
ALMCC
Algeria Mission Control Centre
ARCC
Aeronautical Rescue Coordination Centre
ARMCC
Argentina Mission Control Centre
ASMCC
South Africa Mission Control Centre
ATSU
Air Traffic Service Unit
AUMCC
Australia Mission Control Centre
BDS
BeiDou Navigation Satellite System of China (People’s Republic of)
BRMCC
Brazil Mission Control Centre
BT
Begin Transmission
C/S
Cospas-Sarsat
CDDR
Central Data Distribution Region
CHMCC
Chile MCC
CMC
Cospas Mission Centre (Russian Federation)
CMCC
Canada Mission Control Centre
CNMCC
China Mission Control Centre
COSPAS
Cosmicheskaya Sistema Poiska Avariynich Sudov (Russian for Space
System for the Search of Vessels in Distress)
CSTA
Cospas-Sarsat Type Approval
CYMCC
Cyprus Mission Control Centre
DDP
Data Distribution Plan
DDR
Data Distribution Region
DOA
Difference of Arrival
EDDR
Eastern Data Distribution Region
EHE
Expected Horizontal Error
ELT
Emergency Locator Transmitter
ELT(DT)
Emergency Locator Transmitter for Distress Tracking
EPIRB
Emergency Position-Indicating Radio Beacon
FGB
First Generation Beacon (per document C/S T.001)
FMCC
France Mission Control Centre
FOA
Frequency of Arrival
GADSS
Global Aeronautical Distress and Safety System
Galileo
European global navigation satellite system
GEOLUT
Local User Terminal for GEOSAR
GEOSAR
Geostationary Earth Orbit Search and Rescue
GHz
Giga Hertz
GLONASS
Russian global navigation satellite system
GMDSS
Global Maritime Distress and Safety System

A-2

ACRONYM
TERMINOLOGY
GNSS
Global Navigation Satellite System
GOES
Geostationary Operational Environmental Satellite
GPS
Global Positioning System (USA)
GRMCC
Greece Mission Control Centre
Hex ID
Hexadecimal identifier
HKMCC
Hong Kong Mission Control Centre
IAMSAR
International Aeronautical and Maritime Search and Rescue
IBRD
International Beacon Registration Database
ICAO
International Civilian Aviation Organization
IDMCC
Indonesia Mission Control Centre
IMO
International Maritime Organization
INMCC
India Mission Control Centre
INSAT
Indian Satellite
ITMCC
Italy Mission Control Centre
ITU
International Telecommunication Union
JAMCC
Japan Mission Control Centre
JRCC
Joint Rescue Coordination Centre
KOMCC
Korea Mission Control Centre
LADR
Location of an Aircraft in Distress Repository
LEOLUT
Local User Terminal for LEOSAR
LEOSAR
Low-altitude Earth Orbit Search and Rescue
LP-STD
Location Protocol - Standard
LUT
Local User Terminal
LUT ID
Local User Terminal Identifier
MCC
Mission Control Centre
MEOLUT
Local User Terminal for MEOSAR
MEOSAR
Medium-altitude Earth Orbit Search and Rescue
MHz
Mega Hertz
MID
Maritime Identification Digits
MMSI
Maritime Mobile Service Identity
MSG
Message
MSG
Meteosat Second Generation (EUMETSAT Satellite)
MTG
Meteosat Third Generation (EUTMETSAT Satellite)
MYMCC
Malaysia Mission Control Center
NM
Nautical Mile
NMCC
Norway Mission Control Centre
NOCR
Notification of Country of Registration
NIMCC
Nigeria Mission Control Centre
NWPDDR
North-West Pacific Data Distribution Region
PAMCC
Pakistan Mission Control Centre
PDF
Protected Data Field
PEMCC
Peru Mission Control Centre
PLB
Personal Locator Beacon

A-3

ACRONYM
TERMINOLOGY
QAMCC
Qatar Mission Control Center
RCC
Rescue Coordination Centre
REF
Reference
RLM
Return Link Message
RLS
Return Link Service
RLSP
Return Link Service Provider
SAMCC
Saudi Arabia Mission Control Center
SAR
Search and Rescue
SARP
Search and Rescue Processor
SARR
Search and Rescue Repeater
SARSAT
Search and Rescue Satellite-Aided Tracking
SCDDR
South Central Data Distribution Region
SGB
Second Generation Beacon (per document C/S T.018)
SID
Standard Interface Description
SIMCC
Singapore Mission Control Centre
SIT
Subject Indicator Type
SOLAS
Safety of Life at Sea
SPMCC
Spain Mission Control Centre
SPOC
Search and Rescue Point of Contact
SRR
Search and Rescue Region
SSAS
Ship Security Alert System
SSR
Secondary Surveillance Radar
SWPDDR
South-West Pacific Data Distribution Region
TAC
Type-Approval Certificate (number)
TAMCC
ITDC Mission Control Centre (Chinese Taipei)
TCA
Time of Closest Approach
TDOA
Time Difference of Arrival
TGMCC
Togo Mission Control Center
THMCC
Thailand Mission Control Centre
TOA
Time of Arrival
TRMCC
Türkiye Mission Control Centre
UKMCC
United Kingdom of Great Britain and Northern Ireland Mission
Control Centre
USMCC
USA Mission Control Centre
UTC
Universal Coordinated Time
VNMCC
Vietnam Mission Control Centre
WDDR
Western Data Distribution Region
Abbreviations and acronyms used in this document are also defined in document
C/S S.011 “Cospas-Sarsat Glossary”, available on the Cospas-Sarsat website at
https://www.cospas-sarsat.int/en/documents-pro/system-documents
- END OF ANNEX A –

B-1

ANNEX B
LIST OF MID (COUNTRY CODES)
This table is a copy of the list of MID (Maritime Identification Digits) on the Cospas-Sarsat
website (as of 1 December 2021) (see also ITU website at https://www.itu.int/en/ITU-
R/terrestrial/fmd/Pages/mid.aspx).
Name
MID
Abrv 3 Abrv 10
Adelie Land

ADE
ADELIELAND
Afghanistan

AFG
AFGHAN
Alaska (State of) (USA)

ALA
ALASKA
Albania

ALB
ALBANIA
Algeria

ALG
ALGERIA
American Samoa

ASA
SAMOA USA
Andorra

AND
ANDORRA
Angola

ANG
ANGOLA
Anguilla

ANA
ANGUILLA
Antigua and Barbuda

ANT
ANTIGUA
Antigua and Barbuda

ANT
ANTIGUA
Argentina

ARG
ARGENTINA
Armenia

ARM
ARMENIA
Aruba

ARU
ARUBA
Ascension Island

ASC
ASCENSION
Australia

AUS
AUSTRALIA
Austria

AUT
AUSTRIA
Azerbaijan

AZR
AZERBAIJAN
Azores

AZC
AZORES
Bahamas

BAA
BAHAMAS
Bahamas

BAA
BAHAMAS
Bahamas

BAA
BAHAMAS
Bahrain

BAH
BAHRAIN
Bangladesh

BAN
BANGLADESH
Barbados

BAR
BARBADOS
Belarus

BLR
BELARUS
Belgium

BEL
BELGIUM
Belize

BEZ
BELIZE
Benin

BEN
BENIN
Bermuda

BER
BERMUDA
Bhutan

BHU
BHUTAN
Bolivia

BOL
BOLIVIA
Bosnia and Herzegovina

BOS
BOSNIAHERZ
Botswana

BOT
BOTSWANA
Brazil

BRA
BRAZIL

B-2

Name
MID
Abrv 3 Abrv 10
British Virgin Islands

BVI
VIRGIN GB
Brunei Darussalam

BRU
BRUNEI
Bulgaria

BUL
BULGARIA
Burkina Faso

BUF
BURKINA FS
Burundi

BUI
BURUNDI
Cambodia

CMB
CAMBODIA
Cambodia

CMB
CAMBODIA
Cameroon

CAM
CAMEROON
Canada

CAN
CANADA
Cape Verde

CAP
CAPE VERDE
Cayman Islands

CAY
CAYMAN IS
Central African Republic

CAR
CENAFR REP
Chad

CHA
CHAD
Chile

CHI
CHILE
China

CHN
CHINA
China

CHN
CHINA
China

CHN
CHINA
Chinese Taipei

TAI
TAIPEI
Christmas Island

CHR
CHRISTMAS
Cocos (Keeling) Islands

COC
COCOS ISLE
Colombia

COL
COLOMBIA
Comoros

COM
COMOROS
Comoros

COM
COMOROS
Congo

CON
CONGO
Cook Islands

COO
COOK ISLES
Costa Rica

COS
COSTA RICA
Côte d'Ivoire (Ivory Coast)

IVO
IVORY COAST
Croatia

CRT
CROATIA
Crozet Archipelago

CRP
CROZET
Cuba

CUB
CUBA
Cyprus

CYP
CYPRUS
Cyprus

CYP
CYPRUS
Cyprus

CYP
CYPRUS
Czech Republic

CZH
CZECH REP
Democratic People's Republic of Korea

KDR
KOREA NOR
Democratic Republic of the Congo

ZAI
ZAIRE
Denmark

DEN
DENMARK
Denmark

DEN
DENMARK
Djibouti

DJI
DJIBOUTI
Dominica

DOM
DOMINICA
Dominican Republic

DOR
DOMINICAN
Ecuador

ECU
ECUADOR

B-3

Name
MID
Abrv 3 Abrv 10
Egypt

EGY
EGYPT
El Salvador

ELS
ELSALVADOR
Equatorial Guinea

EQG
EQ GUINEA
Eritrea

ERT
ERITREA
Estonia

EST
ESTONIA
Eswatini

SWA
ESWATINI
Ethiopia

ETH
ETHIOPIA
Falkland Islands (Malvinas)1

FAL
FALKLAND I
Faroe Islands

FAR
FARO ISLE
Fiji

FIJ
FIJI
Finland

FIN
FINLAND
France

FRA
FRANCE
France

FRA
FRANCE
France

FRA
FRANCE
French Polynesia

PLY
POLYNESIA
Gabon

GAB
GABON REP
Gambia

GAM
GAMBIA
Georgia

GOG
GEORGIA
Germany

GER
GERMANY
Germany

GER
GERMANY
Ghana

GHA
GHANA
Gibraltar

GIB
GIBRALTAR
Greece

GRE
GREECE
Greece

GRE
GREECE
Greece

GRE
GREECE
Greece

GRE
GREECE
Greenland

GRN
GREENLAND
Grenada

GRA
GRENADA
Guadeloupe (French Dept. of)

GUA
GUADELOUPE
Guatemala

GUT
GUATEMALA
Guiana (French Dept. of)

GUI
GUIANA
Guinea

GUN
GUINEA REP
Guinea-Bissau

GUB
GUINEA BIS
Guyana

GUY
GUYANA
Haiti

HAI
HAITI
Honduras

HON
HONDURAS
Hong Kong, China

HKG
HONG KONG
Hungary

HUN
HUNGARY
Iceland

ICE
ICELAND
1 A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and the
Northern Island concerning the sovereignty over the Falkland Islands (Malvinas).

B-4

Name
MID
Abrv 3 Abrv 10
India

IND
INDIA
Indonesia

INO
INDONESIA
Iran

IRN
IRAN
Iraq

IRQ
IRAQ
Ireland

IRE
IRELAND
Israel

ISR
ISRAEL
Italy

ITA
ITALY
Jamaica

JAM
JAMAICA
Japan

JPN
JAPAN
Japan

JPN
JAPAN
Jordan

JOR
JORDAN
Kazakhstan

KAZ
KAZAKHSTAN
Kenya

KEN
KENYA
Kerguelen Islands

KER
KERGUELEN
Kiribati

KIR
KIRIBATI
Korea (Republic of)

KOR
KOREA SOU
Korea (Republic of)

KOR
KOREA SOU
Kuwait

KUW
KUWAIT
Kyrgyz Republic

KYR
KYRGYZIA
Laos

LAO
LAO
Latvia

LAT
LATVIA
Lebanon

LEB
LEBANON
Lesotho

LES
LESOTHO
Liberia

LIB
LIBERIA
Liberia

LIB
LIBERIA
Libya

LBY
LIBYA
Liechtenstein

LIE
LIECHTEN
Lithuania

LIT
LITHUANIA
Luxembourg

LUX
LUXEMBOURG
Macao, China

MAC
MACAO
Madagascar

MAD
MADAGASCAR
Madeira

MAE
MADEIRA
Malawi

MAW
MALAWI
Malaysia

MLY
MALAYSIA
Maldives

MAV
MALDIVES
Mali

MLI
MALI
Malta

MAL
MALTA
Malta

MAL
MALTA
Malta

MAL
MALTA
Malta

MAL
MALTA
Malta

MAL
MALTA
Marshall Islands

MAR
MARSHALL I

B-5

Name
MID
Abrv 3 Abrv 10
Martinique (French Dept. of)

MTQ
MARTINIQUE
Mauritania

MAA
MAURITANIA
Mauritius

MAU
MAURITIUS
Mexico

MEX
MEXICO
Micronesia

MIC
MICRONESIA
Moldova

MOL
MOLDOVA
Monaco

MON
MONACO
Mongolia

MNG
MONGOLIA
Montenegro

MNT
MONTENEGRO
Montserrat

MOT
MONTSERRAT
Morocco

MOR
MOROCCO
Mozambique

MOZ
MOZAMBIQUE
Myanmar

BUR
BURMA
Namibia

NAM
NAMIBIA
Nauru

NAU
NAURU
Nepal

NEP
NEPAL
Netherlands (The)

NET
NETHERLAND
Netherlands (The)

NET
NETHERLAND
Netherlands (The)

NET
NETHERLAND
Netherlands Antilles (formerly-).
Sint Maarten (Dutch part); Bonaire,
Sint Eustatius and Saba; and Curacao

NEA
N ANTILLES
New Caledonia

NCA
CALEDONIA
New Zealand

NZL
NEWZEALAND
Nicaragua

NIC
NICARAGUA
Niger

NIG
NIGER
Nigeria

NIA
NIGERIA
Niue

NIU
NIUE ISLE
North Macedonia (Republic of)

MKD
NORTH MAC
Northern Mariana Islands

MAI
MARIANA IS
Norway

NOR
NORWAY
Norway

NOR
NORWAY
Norway

NOR
NORWAY
Oman

OMN
OMAN
Pakistan

PAK
PAKISTAN
Palau

PAL
PALAU
Palestine

PAA
PALESTINE
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA

B-6

Name
MID
Abrv 3 Abrv 10
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Panama

PAN
PANAMA
Papua New Guinea

PAP
PAPUA NG
Paraguay

PAR
PARAGUAY
Peru

PER
PERU
Philippines

PHI
PHILIPPINE
Pitcairn

PIT
PITCAIRN I
Poland

POL
POLAND
Portugal

POR
PORTUGAL
Puerto Rico

PUE
PUERTORICO
Qatar

QAT
QATAR
Réunion (La) (same country code for
Mayotte)

REU
REUNION
Romania

ROM
ROMANIA
Russian Federation

RUS
RUSSIA
Rwanda

RWA
RWANDA
Saint Kitts and Nevis

SKN
ST KITTS
Saint Lucia

SLU
ST LUCIA
Saint Paul and Amsterdam Islands

SPL
ST PAUL
Saint Vincent and the Grenadines

SVG
ST VINCENT
Saint Vincent and the Grenadines

SVG
ST VINCENT
Saint Vincent and the Grenadines

SVG
ST VINCENT
Samoa

WSA
WEST SAMOA
San Marino

SAN
SAN MARINO
Sao Tome and Principe

SAO
SAO TOME
Saudi Arabia

SAU
SAUDI
Senegal

SEN
SENEGAL
Serbia

SER
SERBIA
Seychelles

SEY
SEYCHELLES
Sierra Leone

SIL
SIERRA LEO
Singapore

SIN
SINGAPORE
Singapore

SIN
SINGAPORE
Singapore

SIN
SINGAPORE
Singapore

SIN
SINGAPORE
Slovak Republic

SLV
SLOVAKIA
Slovenia

SVN
SLOVENIA

B-7

Name
MID
Abrv 3 Abrv 10
Solomon Islands

SOL
SOLOMON IS
Somalia

SOM
SOMALI
South Africa

SAF
SO AFRICA
South Sudan

SSD
SOUTHSUDAN
Spain

SPA
SPAIN
Spain

SPA
SPAIN
Sri Lanka

SRI
SRI LANKA
St. Helena

SHE
ST HELENA
St. Pierre and Miquelon (French Dept. of)

SPI
ST PIERRE
Sudan

SUD
SUDAN
Suriname

SUR
SURINAME
Sweden

SWE
SWEDEN
Sweden

SWE
SWEDEN
Switzerland

SWT
SWISS
Syria

SYR
SYRIA
Tajikistan

TJK
TAJIKISTAN
Tanzania

TAN
TANZANIA
Tanzania

TAN
TANZANIA
Thailand

THA
THAILAND
Timor-Leste

TIM
TIMORLESTE
Togo

TOG
TOGO
Tonga

TON
TONGA
Trinidad and Tobago

TAT
TRINIDAD
Tunisia

TUN
TUNISIA
Türkiye

TUR
TURKIYE
Turkmenistan

TKM
TURKMENIST
Turks and Caicos Islands

TUK
CAICOS IS
Tuvalu

TUV
TUVALU IS
Uganda

UGA
UGANDA
Ukraine

UKR
UKRAINE
United Arab Emirates

UAE
UAE
United Arab Emirates

UAE
UAE
United Kingdom of Great Britain and
Northern Ireland

UKM
G BRITAIN
United Kingdom of Great Britain and
Northern Ireland

UKM
G BRITAIN
United Kingdom of Great Britain and
Northern Ireland

UKM
G BRITAIN
United Kingdom of Great Britain and
Northern Ireland

UKM
G BRITAIN
United States of America

USA
USA
United States of America

USA
USA

B-8

Name
MID
Abrv 3 Abrv 10
United States of America

USA
USA
United States of America

USA
USA
United States of America

USA
USA
United States Virgin Islands

USV
VIRGIN US
Uruguay

URU
URUGUAY
Uzbekistan

UZB
UZBEKISTAN
Vanuatu

VAN
VANUATU
Vanuatu

VAN
VANUATU
Vatican City State

VAT
VATICAN
Venezuela

VEN
VENEZUELA
Vietnam

VIE
VIETNAM
Wallis and Futuna Islands

WAL
WALLIS IS
Yemen

YEM
YEMEN
Yemen

YEM
YEMEN
Zambia

ZAM
ZAMBIA
Zimbabwe

ZIM
ZIMBABWE

B-9

This table listing the MID codes in order uses data from the Cospas-Sarsat website
downloaded (as of 1 November 2019) (see also ITU website at https://www.itu.int/en/ITU-
R/terrestrial/fmd/Pages/mid.aspx).
MID
Name
Abrv 3
Abrv 10

Albania
ALB
ALBANIA

Andorra
AND
ANDORRA

Austria
AUT
AUSTRIA

Azores
AZC
AZORES

Belgium
BEL
BELGIUM

Belarus
BLR
BELARUS

Bulgaria
BUL
BULGARIA

Vatican City State
VAT
VATICAN

Cyprus
CYP
CYPRUS

Cyprus
CYP
CYPRUS

Germany
GER
GERMANY

Cyprus
CYP
CYPRUS

Georgia
GOG
GEORGIA

Moldova
MOL
MOLDOVA

Malta
MAL
MALTA

Armenia
ARM
ARMENIA

Germany
GER
GERMANY

Denmark
DEN
DENMARK

Denmark
DEN
DENMARK

Spain
SPA
SPAIN

Spain
SPA
SPAIN

France
FRA
FRANCE

France
FRA
FRANCE

France
FRA
FRANCE

Malta
MAL
MALTA

Finland
FIN
FINLAND

Faroe Islands
FAR
FARO ISLE

United Kingdom of Great Britain and
Northern Ireland
UKM
G BRITAIN

United Kingdom of Great Britain and
Northern Ireland
UKM
G BRITAIN

United Kingdom of Great Britain and
Northern Ireland
UKM
G BRITAIN

United Kingdom of Great Britain and
Northern Ireland
UKM
G BRITAIN

Gibraltar
GIB
GIBRALTAR

Greece
GRE
GREECE

Croatia
CRT
CROATIA

Greece
GRE
GREECE

B-10

MID
Name
Abrv 3
Abrv 10

Greece
GRE
GREECE

Greece
GRE
GREECE

Morocco
MOR
MOROCCO

Hungary
HUN
HUNGARY

Netherlands (The)
NET
NETHERLAND

Netherlands (The)
NET
NETHERLAND

Netherlands (The)
NET
NETHERLAND

Italy
ITA
ITALY

Malta
MAL
MALTA

Malta
MAL
MALTA

Ireland
IRE
IRELAND

Iceland
ICE
ICELAND

Liechtenstein
LIE
LIECHTEN

Luxembourg
LUX
LUXEMBOURG

Monaco
MON
MONACO

Madeira
MAE
MADEIRA

Malta
MAL
MALTA

Norway
NOR
NORWAY

Norway
NOR
NORWAY

Norway
NOR
NORWAY

Poland
POL
POLAND

Montenegro
MNT
MONTENEGRO

Portugal
POR
PORTUGAL

Romania
ROM
ROMANIA

Sweden
SWE
SWEDEN

Sweden
SWE
SWEDEN

Slovak Republic
SLV
SLOVAKIA

San Marino
SAN
SAN MARINO

Switzerland
SWT
SWISS

Czech Republic
CZH
CZECH REP

Türkiye
TUR
TURKIYE

Ukraine
UKR
UKRAINE

Russian Federation
RUS
RUSSIA

North Macedonia (Republic of)
MKD
NORTH MAC

Latvia
LAT
LATVIA

Estonia
EST
ESTONIA

Lithuania
LIT
LITHUANIA

Slovenia
SVN
SLOVENIA

Serbia
SER
SERBIA

Anguilla
ANA
ANGUILLA

Alaska (State of) (USA)
ALA
ALASKA

Antigua and Barbuda
ANT
ANTIGUA

B-11

MID
Name
Abrv 3
Abrv 10

Antigua and Barbuda
ANT
ANTIGUA

Netherlands Antilles (formerly-).
Sint Maarten (Dutch part); Bonaire,
Sint Eustatius and Saba; and Curacao
NEA
N ANTILLES

Aruba
ARU
ARUBA

Bahamas
BAA
BAHAMAS

Bahamas
BAA
BAHAMAS

Bermuda
BER
BERMUDA

Bahamas
BAA
BAHAMAS

Belize
BEZ
BELIZE

Barbados
BAR
BARBADOS

Canada
CAN
CANADA

Cayman Islands
CAY
CAYMAN IS

Costa Rica
COS
COSTA RICA

Cuba
CUB
CUBA

Dominica
DOM
DOMINICA

Dominican Republic
DOR
DOMINICAN

Guadeloupe (French Dept. of)
GUA
GUADELOUPE

Grenada
GRA
GRENADA

Greenland
GRN
GREENLAND

Guatemala
GUT
GUATEMALA

Honduras
HON
HONDURAS

Haiti
HAI
HAITI

United States of America
USA
USA

Jamaica
JAM
JAMAICA

Saint Kitts and Nevis
SKN
ST KITTS

Saint Lucia
SLU
ST LUCIA

Mexico
MEX
MEXICO

Martinique
MTQ
MARTINIQUE

Montserrat
MOT
MONTSERRAT

Nicaragua
NIC
NICARAGUA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Puerto Rico
PUE
PUERTORICO

El Salvador
ELS
ELSALVADOR

St. Pierre and Miquelon
SPI
ST PIERRE

Trinidad and Tobago
TAT
TRINIDAD

B-12

MID
Name
Abrv 3
Abrv 10

Turks and Caicos Islands
TUK
CAICOS IS

United States of America
USA
USA

United States of America
USA
USA

United States of America
USA
USA

United States of America
USA
USA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Panama
PAN
PANAMA

Saint Vincent and the Grenadines
SVG
ST VINCENT

Saint Vincent and the Grenadines
SVG
ST VINCENT

Saint Vincent and the Grenadines
SVG
ST VINCENT

British Virgin Islands
BVI
VIRGIN GB

United States Virgin Islands
USV
VIRGIN US

Afghanistan
AFG
AFGHAN

Saudi Arabia
SAU
SAUDI

Bangladesh
BAN
BANGLADESH

Bahrain
BAH
BAHRAIN

Bhutan
BHU
BHUTAN

China
CHN
CHINA

China
CHN
CHINA

China
CHN
CHINA

Chinese Taipei
TAI
TAIPEI

Sri Lanka
SRI
SRI LANKA

India
IND
INDIA

Iran
IRN
IRAN

Azerbaijan
AZR
AZERBAIJAN

Iraq
IRQ
IRAQ

Israel
ISR
ISRAEL

Japan
JPN
JAPAN

Japan
JPN
JAPAN

Turkmenistan
TKM
TURKMENIST

Kazakhstan
KAZ
KAZAKHSTAN

Uzbekistan
UZB
UZBEKISTAN

Jordan
JOR
JORDAN

Korea (Republic of)
KOR
KOREA SOU

Korea (Republic of)
KOR
KOREA SOU

Palestine
PAA
PALESTINE

Democratic People's Republic of Korea
KDR
KOREA NOR

Kuwait
KUW
KUWAIT

Lebanon
LEB
LEBANON

B-13

MID
Name
Abrv 3
Abrv 10

Kyrgyz Republic
KYR
KYRGYZIA

Macao, China
MAC
MACAO

Maldives
MAV
MALDIVES

Mongolia
MNG
MONGOLIA

Nepal
NEP
NEPAL

Oman
OMN
OMAN

Pakistan
PAK
PAKISTAN

Qatar
QAT
QATAR

Syria
SYR
SYRIA

United Arab Emirates
UAE
UAE

United Arab Emirates
UAE
UAE

Tajikistan
TJK
TAJIKISTAN

Yemen
YEM
YEMEN

Yemen
YEM
YEMEN

Hong Kong, China
HKG
HONG KONG

Bosnia and Herzegovina
BOS
BOSNIAHERZ

Adelie Land
ADE
ADELIELAND

Australia
AUS
AUSTRALIA

Myanmar
BUR
BURMA

Brunei Darussalam
BRU
BRUNEI

Micronesia
MIC
MICRONESIA

Palau
PAL
PALAU

New Zealand
NZL
NEWZEALAND

Cambodia
CMB
CAMBODIA

Cambodia
CMB
CAMBODIA

Christmas Island
CHR
CHRISTMAS

Cook Islands
COO
COOK ISLES

Fiji
FIJ
FIJI

Cocos (Keeling) Islands
COC
COCOS ISLE

Indonesia
INO
INDONESIA

Kiribati
KIR
KIRIBATI

Laos
LAO
LAO

Malaysia
MLY
MALAYSIA

Northern Mariana Islands
MAI
MARIANA IS

Marshall Islands
MAR
MARSHALL I

New Caledonia
NCA
CALEDONIA

Niue
NIU
NIUE ISLE

Nauru
NAU
NAURU

French Polynesia
PLY
POLYNESIA

Philippines
PHI
PHILIPPINE

Timor-Leste
TIM
TIMORLESTE

Papua New Guinea
PAP
PAPUA NG

B-14

MID
Name
Abrv 3
Abrv 10

Pitcairn
PIT
PITCAIRN I

Solomon Islands
SOL
SOLOMON IS

American Samoa
ASA
SAMOA USA

Samoa
WSA
WEST SAMOA

Singapore
SIN
SINGAPORE

Singapore
SIN
SINGAPORE

Singapore
SIN
SINGAPORE

Singapore
SIN
SINGAPORE

Thailand
THA
THAILAND

Tonga
TON
TONGA

Tuvalu
TUV
TUVALU IS

Vietnam
VIE
VIETNAM

Vanuatu
VAN
VANUATU

Vanuatu
VAN
VANUATU

Wallis and Futuna Islands
WAL
WALLIS IS

South Africa
SAF
SO AFRICA

Angola
ANG
ANGOLA

Algeria
ALG
ALGERIA

Saint Paul and Amsterdam Islands
SPL
ST PAUL

Ascension Island
ASC
ASCENSION

Burundi
BUI
BURUNDI

Benin
BEN
BENIN

Botswana
BOT
BOTSWANA

Central African Republic
CAR
CENAFR REP

Cameroon
CAM
CAMEROON

Congo
CON
CONGO

Comoros
COM
COMOROS

Cape Verde
CAP
CAPE VERDE

Crozet Archipelago
CRP
CROZET

Côte d'Ivoire (Ivory Coast)
IVO
IVORYCOAST

Comoros
COM
COMOROS

Djibouti
DJI
DJIBOUTI

Egypt
EGY
EGYPT

Ethiopia
ETH
ETHIOPIA

Eritrea
ERT
ERITREA

Gabon
GAB
GABON REP

Ghana
GHA
GHANA

Gambia
GAM
GAMBIA

Guinea-Bissau
GUB
GUINEA BIS

Equatorial Guinea
EQG
EQ GUINEA

Guinea
GUN
GUINEA REP

Burkina Faso
BUF
BURKINA FS

B-15

MID
Name
Abrv 3
Abrv 10

Kenya
KEN
KENYA

Kerguelen Islands
KER
KERGUELEN

Liberia
LIB
LIBERIA

Liberia
LIB
LIBERIA

South Sudan
SSD
SOUTHSUDAN

Libya
LBY
LIBYA

Lesotho
LES
LESOTHO

Mauritius
MAU
MAURITIUS

Madagascar
MAD
MADAGASCAR

Mali
MLI
MALI

Mozambique
MOZ
MOZAMBIQUE

Mauritania
MAA
MAURITANIA

Malawi
MAW
MALAWI

Niger
NIG
NIGER

Nigeria
NIA
NIGERIA

Namibia
NAM
NAMIBIA

Reunion (same country code for Mayotte)
REU
REUNION

Rwanda
RWA
RWANDA

Sudan
SUD
SUDAN

Senegal
SEN
SENEGAL

Seychelles
SEY
SEYCHELLE

St. Helena
SHE
ST HELENA

Somalia
SOM
SOMALI

Sierra Leone
SIL
SIERRA LEO

Sao Tome and Principe
SAO
SAO TOME

Eswatini
SWA
ESWATINI

Chad
CHA
CHAD

Togo
TOG
TOGO

Tunisia
TUN
TUNISIA

Tanzania
TAN
TANZANIA

Uganda
UGA
UGANDA

Democratic Republic of the Congo
ZAI
ZAIRE

Tanzania
TAN
TANZANIA

Zambia
ZAM
ZAMBIA

Zimbabwe
ZIM
ZIMBABWE

Argentina
ARG
ARGENTINA

Brazil
BRA
BRAZIL

Bolivia
BOL
BOLIVIA

Chile
CHI
CHILE

Colombia
COL
COLOMBIA

Ecuador
ECU
ECUADOR

B-16

MID
Name
Abrv 3
Abrv 10

Falkland Islands (Malvinas) 2
FAL
FALKLAND I

Guiana (French Dept. Of)
GUI
GUIANA

Guyana
GUY
GUYANA

Paraguay
PAR
PARAGUAY

Peru
PER
PERU

Suriname
SUR
SURINAME

Uruguay
URU
URUGUAY

Venezuela
VEN
VENEZUELA
- END OF ANNEX B -
2 A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and the
Northern Island concerning the sovereignty over the Falkland Islands (Malvinas).

C-1

ANNEX C
COSPAS-SARSAT DATA DISTRIBUTION REGIONS
C.1
WESTERN DDR
Figure C.1: Western DDR Map

![Image 1 from page 136](/images/cospas-sarsat/G-series/G007/G007_page_136_img_1.png)

C-2

Countries/Regions and MIDs Supported by the Western DDR MCCs:
ARMCC
Argentina

Falklands
Islands/Malvinas

BRMCC
Brazil

Ascension

CHMCC
Bolivia

Chile

Paraguay

Uruguay

CMCC
Canada

St. Pierre and
Miquelon

PEMCC
Peru

USMCC
Alaska

Aruba

Bahamas
308/309/311
Barbados

Belize

Bermuda

British Virgin
Islands

Cayman Islands

Colombia

Costa Rica

Cuba

Dominican
Republic 327
Ecuador

El Salvador

Grenada

Guatemala

Guyana

Haiti

Honduras

Jamaica

Marshall
Islands

Mexico

Micronesia

Netherlands
Antilles

Nicaragua

Northern
Mariana
Islands

Palau

Panama
351/352/353/354/
355/356/357/370/
371/372/373/374
Puerto Rico

St. Vincent
and the
Grenadines
375/376/377
Trinidad and
Tobago

Turks and
Caicos Islands

USA
338/366/367/368/

US Virgin
Islands

Venezuela

C-3

C.2 NORTH WEST PACIFIC DDR
Figure C.2: North West Pacific DDR Map
Countries/Regions and MIDs Supported by the North-West Pacific DDR MCCs
CNMCC
China (P.R. of)
412/413
HKMCC
Hong Kong,
China

Macao, China

Philippines

Democratic People’s
Rep. of Korea

JAMCC
Japan
431/432
KOMCC
Korea (Rep. of)
440/441
TAMCC
Chinese Taipei

VNMCC
Cambodia
514/515
Laos

Viet Nam

![Image 1 from page 138](/images/cospas-sarsat/G-series/G007/G007_page_138_img_1.png)

C-4

C.3  SOUTH WEST PACIFIC DDR
Figure C.3: South West Pacific DDR Map
Countries/Regions and MIDs Supported by the South West Pacific DDR MCCs
ASMCC
Angola

Botswana

Burundi

Dem. Rep. of
Congo 676
Eswatini

Lesotho

Malawi

Mozambique

Namibia

Rwanda

South Africa

St. Helena

Uganda

Zambia

Zimbabwe

AUMCC
Adelie Land

American
Samoa 559
Australia

Christmas Island

Cocos Islands

Cook Islands

Fiji

Kiribati

Nauru

New Caledonia

New Zealand

Niue

Papua New
Guinea 553
Saint Paul &
Amsterdam 607
Samoa

Solomon
Islands 557
Tonga

Tuvalu

Vanuatu

Wallis and
Futuna 578
IDMCC
Indonesia 525
Timor-Leste 550
SIMCC
Brunei

Malaysia

Myanmar

Singapore
563/564/565
THMCC
Thailand 567

![Image 1 from page 139](/images/cospas-sarsat/G-series/G007/G007_page_139_img_1.png)

C-5

C.4 CENTRAL DDR
Figure C.4: Central DDR Map

![Image 1 from page 140](/images/cospas-sarsat/G-series/G007/G007_page_140_img_1.png)

C-6

Countries/Regions and MIDs Supported by the Central DDR MCCs
CYMCC
Cyprus         209/210/212
FMCC
Andorra

Anguilla

Antigua and
Barbuda
304/305
Austria

Azores

Belgium

Chad

Djibouti

Comoros

Crozet
Archipelago 618
Dominica

France
226/227/228
French Guiana

French Polynesia

Germany
211/218
Gibraltar

Guadeloupe

Kerguelen
Islands 635
Liechtenstein
(Swiss) 252
Luxemburg

Madagascar

Madeira 255
Martinique

Mauritius

Monaco

Montserrat

Morocco

Netherlands
244/245/246
Pitcairn

Portugal

Reunion/Mayotte

Saint Kitts and
Nevis 341
Saint Lucia

Suriname

Switzerland

Tunisia    672
GRMCC
Greece   237/239/240
ITMCC
Albania

Bosnia &
Herzegovina

Croatia

Eritrea

Ethiopia

Israel

Italy

Kenya

Malta
215/248/249/256
Montenegro

North Macedonia

Palestine

San Marino

Serbia

Slovenia

Somalia

South Sudan

Sudan

Vatican City

NMCC
Denmark
219/220
Estonia

Faroe Islands

Finland

Greenland

Iceland

Latvia

Lithuania

Norway
257/258/259
Poland

Sweden     265/266
TRMCC
Afghanistan

Georgia\*

Iran

Iraq

Türkiye

Ukraine*       272
UKMCC
United Kingdom 232/233/234/235
Ireland    250
* See also CMC service area.

C-7

C.5  SOUTH CENTRAL DDR
Figure C.5: South Central DDR Map
Countries/Regions and MIDs Supported by the South-Central DDR MCCs
AEMCC
United Arab Emirates
470/471
ALMCC
Algeria

Burkina Faso

Egypt

Libya

Niger

NIMCC
Declared as “CNO”
See SPMCC
SAMCC
Bahrain

Jordan

Kuwait

Lebanon

Oman

Saudi Arabia

Syria

Yemen
473/475
SPMCC
Benin

Cameroon

Cape Verde

Central
African
Republic 612
Congo

Equatorial Guinea

Gabon

Gambia

Ghana

Guinea

Guinea-Bissau

Ivory Coast

Liberia
636/637
Mali

Mauritania

Sao Tome and
Principe 668
Senegal

Sierra Leone

Spain
224/225
Togo

Nigeria

![Image 1 from page 142](/images/cospas-sarsat/G-series/G007/G007_page_142_img_1.png)

C-8

C.6  EASTERN DDR
Figure C.6: Eastern DDR Map
Countries/Regions and MIDs Supported by the Eastern DDR MCCs
CMC
Armenia

Azerbaijan

Belarus

Bulgaria

Czech
Republic 270
Georgia\*

Hungary

Kazakhstan

Kyrgyz Rep.

Moldova

Mongolia

Romania

Russia

Tajikistan

Turkmenistan

Ukraine\*

Uzbekistan

INMCC
Bangladesh

Bhutan

India

Maldives

Nepal

Seychelles

Sri Lanka

Tanzania
674/677
PAMCC
Pakistan

* See also TRMCC service area.
- END OF ANNEX C -

![Image 1 from page 143](/images/cospas-sarsat/G-series/G007/G007_page_143_img_1.png)

D-1

ANNEX D
HOW TO USE THE IBRD
Annex D is sequence of slides that shows how a SAR Service can use the IBRD. Please send
an email to admin@406registration.com for any questions.

![Image 1 from page 144](/images/cospas-sarsat/G-series/G007/G007_page_144_img_1.png)

![Image 2 from page 144](/images/cospas-sarsat/G-series/G007/G007_page_144_img_2.png)

D-2

![Image 1 from page 145](/images/cospas-sarsat/G-series/G007/G007_page_145_img_1.png)

![Image 2 from page 145](/images/cospas-sarsat/G-series/G007/G007_page_145_img_2.png)

D-3

![Image 1 from page 146](/images/cospas-sarsat/G-series/G007/G007_page_146_img_1.png)

![Image 2 from page 146](/images/cospas-sarsat/G-series/G007/G007_page_146_img_2.png)

D-4

![Image 1 from page 147](/images/cospas-sarsat/G-series/G007/G007_page_147_img_1.png)

![Image 2 from page 147](/images/cospas-sarsat/G-series/G007/G007_page_147_img_2.png)

D-5

![Image 1 from page 148](/images/cospas-sarsat/G-series/G007/G007_page_148_img_1.png)

![Image 2 from page 148](/images/cospas-sarsat/G-series/G007/G007_page_148_img_2.png)

D-6

![Image 1 from page 149](/images/cospas-sarsat/G-series/G007/G007_page_149_img_1.png)

![Image 2 from page 149](/images/cospas-sarsat/G-series/G007/G007_page_149_img_2.png)

D-7

– END OF ANNEX D –
– END OF DOCUMENT –

![Image 1 from page 150](/images/cospas-sarsat/G-series/G007/G007_page_150_img_1.png)

![Image 2 from page 150](/images/cospas-sarsat/G-series/G007/G007_page_150_img_2.png)

Cospas-Sarsat Secretariat
1250 boulevard René-Lévesque West, Suite 4215, Montréal, Québec H3B 4W8 CANADA
Telephone: + 1 514 500 9993
Fax: + 1 514 500 7996
Email: mail@cospas-sarsat.int
Website www.cospas-sarsat.int