Ryan Malloy
4ed92efd69
Cospas-Sarsat specification summaries moved to reference/ for internal use only. Links updated to point to official cospas-sarsat.int site. The extracted images remain in public/ for use in other pages.
670 lines
14 KiB
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670 lines
14 KiB
Markdown
---
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title: "T006: Cospas-Sarsat Orbitography Network Specification C"
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description: "Official Cospas-Sarsat T-series document T006"
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sidebar:
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badge:
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text: "T"
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variant: "note"
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# Extended Cospas-Sarsat metadata
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documentId: "T006"
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series: "T"
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seriesName: "Technical"
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documentType: "specification"
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isLatest: true
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issue: 2
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revision: 4
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documentDate: "October 2024"
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---
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> **📋 Document Information**
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>
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> **Series:** T-Series (Technical)
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> **Version:** Issue 2 - Revision 4
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> **Date:** October 2024
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> **Source:** [Cospas-Sarsat Official Documents](https://www.cospas-sarsat.int/en/documents-pro/system-documents)
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---
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# T006 - T006-OCT-24-2024.pdf
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**Pages:** 12
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---
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COSPAS-SARSAT
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ORBITOGRAPHY NETWORK
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SPECIFICATION
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C/S T.006
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Issue 2 - Revision 4
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COSPAS-SARSAT ORBITOGRAPHY NETWORK SPECIFICATION
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History
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Issue
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Revision
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Date
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Comments
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Approved by the Cospas-Sarsat Council (CSC-7)
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Approved by the Cospas-Sarsat Council (CSC-27)
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Approved by the Cospas-Sarsat Council (CSC-43)
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Approved by the Cospas-Sarsat Council (CSC-47)
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Approved by the Cospas-Sarsat Council (CSC-51)
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Approved by the Cospas-Sarsat Council (CSC-71)
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TABLE OF CONTENTS
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Page
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1.
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INTRODUCTION ..................................................................................................... 1-1
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1.1
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Overview ......................................................................................................... 1-1
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1.2
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Scope ............................................................................................................... 1-1
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1.3
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Reference Documents ..................................................................................... 1-1
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2.
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COSPAS-SARSAT ORBITOGRAPHY NETWORK DESCRIPTION ............... 2-1
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2.1
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Purpose ............................................................................................................ 2-1
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2.2
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Characteristics ................................................................................................. 2-1
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2.3
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Back-up Procedures ......................................................................................... 2-1
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2.4
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List of Orbitography Beacons in System ........................................................ 2-2
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3.
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ORBITOGRAPHY BEACON REQUIREMENTS AND SPECIFICATIONS ... 3-1
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3.1
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Requirements for Supplying an Orbitography Beacon ................................... 3-1
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3.2
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Specification Unique to Orbitography Beacons .............................................. 3-1
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4.
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TIME CALIBRATION BEACON CHARACTERISTICS ................................... 4-1
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ANNEXES:
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Annex A - Commitment of the Orbitography Beacon Provider ........................................... A-1
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1 - 1
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1 - INTRODUCTION
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1.1
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Overview
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The purpose of the Cospas-Sarsat System is to provide distress alert and location data for
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search and rescue (SAR), by using spacecraft and ground facilities to detect and locate distress
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signals and transmit the computed position and other related information to appropriate SAR
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authorities.
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The Doppler technique, used by Local User Terminals that track Cospas-Sarsat low altitude
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Earth orbiting satellites (LEOLUTs) to locate distress signals, needs an accurate determination
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of the satellite position. The Cospas-Sarsat orbitography network is used by LEOLUTs to
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compute accurate satellite ephemeris.
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1.2
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Scope
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This document describes the Cospas-Sarsat orbitography network and gives the specifications
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of its elements.
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1.3
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Reference Documents
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The following documents contain useful information to the understanding of this C/S T.006
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document:
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a)
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Introduction to the Cospas-Sarsat System, C/S G.003;
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b)
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Specification for Cospas-Sarsat 406 MHz Distress Beacons, C/S T.001;
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c)
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Cospas-Sarsat LEOLUT Performance Specification and Design Guidelines,
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C/S T.002;
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d)
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Description of the Payloads Used in the Cospas-Sarsat LEOSAR System, C/S T.003;
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e)
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Cospas-Sarsat Data Distribution Plan, C/S A.001.
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- END OF SECTION 1 –
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2 - 1
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COSPAS-SARSAT ORBITOGRAPHY NETWORK DESCRIPTION
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2.1
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Purpose
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The Cospas-Sarsat 406 MHz system provides world-wide global coverage. All LEOLUTs have
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the capability to locate 406 MHz distress beacons anywhere on the Earth. Achieved location
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accuracy is dependent on various parameters. Of these parameters, satellite orbit ephemeris is
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dealt within the document.
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The contribution to the location error budget due to orbit determination error is required to be
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less than 2 km (see Cospas-Sarsat LEOLUT Performance Specification and Design Guidelines,
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C/S T.002). An efficient way to achieve such accuracy is to perform orbit ephemeris updates
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based on data received from high-quality beacons placed at accurately known locations.
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These high-quality beacons also provide an ideal resource to complete the Quality
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Management System (QMS) objectives stated in section 7 of C/S P.015 “Cospas-Sarsat
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Quality Manual”.
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2.2
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Characteristics
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The network consists of three 406 MHz orbitography beacons located at high latitudes and the
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time reference beacon located at Toulouse, France. The identification and location of these
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beacons are given on the Cospas-Sarsat website www.cospas-sarsat.org. These beacons
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provide sufficient data to allow any Cospas-Sarsat LEOLUT to achieve the specified orbit
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determination accuracy. If an orbitography beacon fails then data from the time calibration
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beacon (see C/S A.001) may be used until the beacon which had failed has been returned to
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service.
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2.3
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Back-up Procedures
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In case of failure of satellite on-board equipment, back-up procedures for updating the orbit
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ephemeris are necessary.
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In order to collect data from the orbitography beacons, the onboard Search and Rescue
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Processor (SARP), including its memory, has to function properly. In case of on-board SARP
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memory failure, the recommended back-up procedures are to update orbit ephemeris using data
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collected from either the Cospas-Sarsat MCC Network or measurements on the satellite
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down-link frequency. Degraded accuracy in orbit ephemeris determination is accepted in this
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back-up mode. The preferred orbit update methods, listed in order of priority for each specific
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payload, is provided at Annex III/D of document C/S A.001 (DDP).
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2 - 2
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2.4
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List of Orbitography Beacons in System
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The orbitography beacons used in the Cospas-Sarsat System are provided by Denmark,
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Norway, the USA and France. The complete list of beacons, including the identification and
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location of each, is provided on the Cospas-Sarsat website www.cospas-sarsat.org.
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- END OF SECTION 2 -
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3 - 1
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3 - ORBITOGRAPHY BEACON REQUIREMENTS AND SPECIFICATIONS
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3.1
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Requirements for Supplying an Orbitography Beacon
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Supplying an Orbitography Beacon:
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An orbitography beacon is supplied by a country accepting the commitment stated
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in Annex A.
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Availability:
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Once an orbitography beacon has been installed, its availability shall be greater than
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95%.
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Location Data:
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The beacon antenna location (longitude, latitude, altitude) shall be provided with a
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three dimensional accuracy better than 10 m. This location shall be given with
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respect to the Bureau International de l'Heure (BIH) Conventional Terrestrial
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System, having a reference ellipsoid defined as follows:
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Semi-Major Axis
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= 6378137 m
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Flattening (Ellipticity)
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= 1/298.2572
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The location of all orbitography beacons is given on the Cospas-Sarsat website
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www.cospas-sarsat.org.
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Antenna Blockage:
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The orbitography beacon antenna should be located to provide the widest possible
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horizon.
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3.2
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Specification Unique to Orbitography Beacons
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Orbitography beacons shall conform to all specifications defined in the
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Specification for Cospas-Sarsat 406 MHz Distress Beacons (document C/S T.001),
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except for the following:
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Repetition period:
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The period between transmissions shall be 30 s + 5%. Variation of the repetition
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period is recommended. If the repetition period is not varied, beacon activation
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must be co-ordinated with other providers of orbitography beacons to prevent
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repeated transmission collisions. The time calibration beacon in Toulouse (which
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must have a constant repetition period) is the standard to which other non-varied
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beacons should be co-ordinated.
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3 - 2
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Transmitted Frequency:
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A crystal warm-up period of up to 2 hours is allowed before transmissions occur.
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Power outages should reset this timer.
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Initial frequency:
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The transmitted frequency shall be 406.022 MHz + 1 kHz. The transmitted
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frequency has been fixed to 406.034 MHz for an orbitography beacon
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specifically introduced in the system for MEOSAR applications. The exact
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transmit frequency of each orbitography beacon is provided on the Cospas-
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Sarsat website www.cospas-sarsat.org.
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Long term frequency stability:
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The transmitted frequency shall not vary more than 1 part in 1010 per day.
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Short term frequency stability:
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The transmitted frequency shall not vary more than 1 part in 1010 in 100 ms.
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Medium term frequency stability:
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The mean slope shall not exceed 5 parts in 1011 per minute. Residual frequency
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variation shall not exceed 1 part in 1010.
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Antenna Characteristics:
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The antenna polarization shall be right-hand circular polarization (RHCP), except
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for the second Toulouse orbitography beacon which transmits at 406.034 MHz and
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has a left-hand circular polarization (LHCP).
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Environmental and Operational Requirements:
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The orbitography beacon is designed to be operated within a controlled
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environment and therefore is not subjected to the thermal or other operational
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requirements specified in C/S T.001.
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Temperature requirements
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Operating temperature range:
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+15o C to +40o C
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Storage temperature range:
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-20o C to +60o C
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Orbitography Protocol:
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The orbitography user protocol must be used. This protocol, defined in C/S T.001,
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is as follows:
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Bits
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Usage
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1-15
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bit synchronization
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16-24
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frame synchronization
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format flag ("0" for short message and "1" for long message)
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protocol flag (set bit to "1")
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27-36
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country code (MID)
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37-39
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orbitography protocol ("000")
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40-81
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seven character orbitography beacon clear text identifier using the
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modified Baudot code (see C/S T.001) The seven characters shall be
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right justified. Characters not used shall be filled with the "space"
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character (100100).
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82-85
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4 binary zeros ("0000")
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national use (set bit to "0")
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108-112
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national use
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3 - 3
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113-144
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optional long message. National use.
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The 15 hexadecimal character identification used by the MCCs describes bits 26
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through 85 (i.e., 60 bits).
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- END OF SECTION 3 -
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4 - 1
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4 - TIME CALIBRATION BEACON CHARACTERISTICS
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This beacon is a special time calibration unit operated by, and under the responsibility of,
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France. This beacon is used to compute the roll-over time of the on-board counter of the
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406 MHz Search and Rescue Processors (SARPs) on Sarsat satellites (i.e., Sarsat time
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calibration), and has the following characteristics:
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it complies with the orbitography beacon performance standard and, therefore, can be
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used as an orbitography beacon;
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each burst transmission is synchronized with UTC, such that the negative-going
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transition of the 23rd bit occurs 216.405 ms + 0.01 ms after the UTC time encoded in
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the burst, as described below; and
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the message field is 144 bits.
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The time calibration beacon transmits UTC in the "long message" format described in
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C/S T.001, where the coding of bits 113 to 144 is as follows:
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Bits
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Usage
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113 - 144
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Universal Coordinated Time as follows:
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113 - 124
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Julian days (BCD)
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125 - 132
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hours (BCD)
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133 - 140
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minutes (BCD)
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141 - 144
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tens of seconds (BCD)
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- END OF SECTION 4 -
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A-1
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ANNEX A
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COMMITMENT OF THE ORBITOGRAPHY BEACON PROVIDER
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The installation and operation of an orbitography beacon is based upon a mutual agreement
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between Cospas-Sarsat and the country providing such a beacon, whereby the Cospas-Sarsat
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Council accepts the proposed provision of the orbitography beacon and the providing country
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agrees to abide to the following principles:
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the host country will assume all costs of providing, operating and maintaining
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the beacon in service;
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in taking the decision where to place an orbitography beacon, both
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Cospas-Sarsat system requirements and the supplying country's requirements
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should be taken into account;
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the supplying country will inform Cospas-Sarsat of the precise location of the
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orbitography beacon;
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the orbitography beacon shall meet the Cospas-Sarsat specifications defined in
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document C/S T.006;
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both Cospas-Sarsat and the country supplying the beacon may request the
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termination of the operation of the orbitography beacon;
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such decision will be subject to discussions and will not take effect until
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12 months after the request has been made by one of the parties involved; and
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in case of a major failure of the beacon, the supplying country will not be
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obliged to supply a new beacon.
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- END OF ANNEX A -
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- END OF DOCUMENT -
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Cospas-Sarsat Secretariat
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1250 René-Lévesque Blvd. West, Suite 4215, Montréal (Québec) H3B 4W8 Canada
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Telephone: +1 514 500 7999
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Fax: +1 514 500 7996
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Email: mail@cospas-sarsat.int
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Website: http://www.cospas-sarsat.int |