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.
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3007 lines
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---
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title: "T003: C/S T.003 - Issue 5 Rev. 1"
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description: "Official Cospas-Sarsat T-series document T003"
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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: "T003"
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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: 5
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revision: 1
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documentDate: "March 2022"
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originalTitle: "C/S T.003 - Issue 5 Rev. 1"
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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 5 - Revision 1
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> **Date:** March 2022
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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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DESCRIPTION OF THE
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406-MHz PAYLOADS USED IN THE
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COSPAS-SARSAT LEOSAR SYSTEM
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C/S T.003
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Issue 5 – Revision 1
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DESCRIPTION OF THE 406-MHz PAYLOADS USED
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IN THE COSPAS-SARSAT LEOSAR SYSTEM
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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 (CSC-1)
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Approved (CSC-7)
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Approved (CSC-9)
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Approved (CSC-15)
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Approved (CSC-25)
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Approved (CSC-27)
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Approved (CSC-31)
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Approved (CSC-37)
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Approved (CSC-39)
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Approved (CSC-41)
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Approved (CSC-45)
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Approved (CSC-53)
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Approved (CSC-57)
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Approved (CSC-59)
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Approved (CSC-66)
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TABLE OF CONTENTS
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Page
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History ................................................................................................................................................. i
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Table of Contents ................................................................................................................................. ii
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List of Figures
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................................................................................................................................. v
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List of Tables
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................................................................................................................................. v
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1.
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INTRODUCTION .............................................................................................. 1-1
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Purpose 1-1
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Scope
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1-1
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Reference Documents .......................................................................................... 1-1
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2.
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COSPAS-SARSAT PARAMETERS ................................................................ 2-1
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Cospas-Sarsat Payloads ........................................................................................ 2-1
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2.1.1
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Cospas-Sarsat Payload Summary ............................................................. 2-1
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2.1.2
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Cospas Payload System Functional Diagram .......................................... 2-1
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Sarsat Payload ...................................................................................................... 2-2
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2.2.1
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Sarsat Payload Summary .......................................................................... 2-3
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2.2.2
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Sarsat Payload System Functional Diagram ............................................ 2-3
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Interoperability Parameters .................................................................................. 2-6
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2.3.1
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Orbit Parameters ....................................................................................... 2-6
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2.3.2
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Input Parameters ....................................................................................... 2-7
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2.3.3
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Output Parameters .................................................................................... 2-8
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2.3.4
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Biphase-L Data Encoding ........................................................................ 2-9
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3.
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COSPAS-SARSAT REPEATERS .................................................................... 3-1
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Cospas Repater ..................................................................................................... 3-1
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Sarsat Repeater SARR-1 (Sarsat-13 and earlier) ................................................. 3-3
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3.2.1
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Sarsat SARR-1 Receivers......................................................................... 3-4
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3.2.2
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Sarsat SARR-1 1544.5 MHz Transmitter ................................................ 3-7
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Sarsat Repeater SARR-2 (Sarsat-14 and after) .................................................. 3-11
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3.3.1
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SARR-2 Power, Telemetry and Command ............................................ 3-12
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3.3.2
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SARR-2 Frequency Generator ............................................................... 3-12
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3.3.3
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SARR-2 SAW FILTER .......................................................................... 3-12
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3.3.4
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Sarsat SARR-2 1544.5 MHz Transmitter .............................................. 3-13
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4.
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COSPAS-SARSAT SARPS ................................................................................ 4-1
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Cospas SARP ....................................................................................................... 4-1
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4.1.1
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Cospas SARP-2 Receiver Processor ........................................................ 4-1
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4.1.2
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Cospas SARP-2 Frame Formatter ............................................................ 4-3
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4.1.3
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Cospas SARP-2 Output Format ............................................................... 4-4
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Sarsat SARP ......................................................................................................... 4-7
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4.2.1
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Sarsat SARP-2 .......................................................................................... 4-7
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4.2.2
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Sarsat SARP-3 ........................................................................................ 4-14
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5.
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COSPAS-SARSAT ANTENNAS ...................................................................... 5-1
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Cospas Antennas .................................................................................................. 5-1
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5.1.1
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Cospas Receive Antennas ........................................................................ 5-1
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5.1.2
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Cospas Transmit Antenna ........................................................................ 5-1
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Sarsat-TIROS Antennas ....................................................................................... 5-3
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5.2.1
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Sarsat-TIROS Receive Antennas ............................................................. 5-3
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5.2.2
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Sarsat-TIROS Transmit Antenna ............................................................. 5-3
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Sarsat-METOP Antennas ..................................................................................... 5-7
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5.3.1
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Sarsat-METOP Receive Antennas ........................................................... 5-7
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5.3.2
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Sarsat-METOP Transmit Antenna ........................................................... 5-8
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Sarsat-NPOESS Antennas .................................................................................... 5-9
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5.4.5
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Sarsat-NPOESS Receive Antenna ......................................................... 5-10
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5.4.6
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Sarsat-NPOESS Transmit Antenna ........................................................ 5-10
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ANNEX A : LIST OF ABBREVIATIONS AND ACRONYMS ........................................ A-1
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ANNEX B : COSPAS-SARSAT LEOSAR FREQUENCIES ............................................. B-1
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B.1 Introduction ......................................................................................................... B-1
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B.2 Frequency Matters ............................................................................................... B-1
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B.2.1 Frequency Requirements ......................................................................... B-1
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B.2.2 Interference.............................................................................................. B-2
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LIST OF FIGURES
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Figure 1-1
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Illustration of Cospas and Sarsat LEOSAR Satellites .................................... 1-2
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Figure 2-1:
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Cospas-Sarsat System Functional Diagram ......................................................... 2-2
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Figure 2-2:
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Sarsat-TIROS Payload and Spacecraft Interface Functional Diagram with SARR-1
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and SARP-2 or SARP-3 ....................................................................................... 2-4
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Figure 2-3:
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Sarsat-METOP Payload and Spacecraft Interface Functional Diagram with SARR-
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1 and SARP-3 ....................................................................................................... 2-5
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Figure 2-4:
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Sarsat Payload and Spacecraft Interface Functional Diagram with SARR-2 and
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SARP-3 ................................................................................................................. 2-6
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Figure 2-5:
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Processed Data Encoding Scheme ....................................................................... 2-9
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Figure 3-1:
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Cospas Repeater Functional Diagram .................................................................. 3-1
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Figure 3-2:
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Cospas 1544.5 MHz Transmitter Functional Diagram ........................................ 3-2
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Figure 3-3:
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Typical Cospas 1544.5 MHz Observed Downlink Signal ................................... 3-3
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Figure 3-4:
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Sarsat SARR-1 Functional Diagram .................................................................... 3-4
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Figure 3-5:
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Sarsat SARR Receiver Functional Diagram ........................................................ 3-6
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Figure 3-6:
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Sarsat SARR Receiver Bandpass Characteristics ................................................ 3-7
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Figure 3-7:
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Sarsat SARR-1 1544.5 MHz Transmitter Functional Diagram ........................... 3-8
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Figure 3-8:
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Sarsat SARR-1 Baseband Frequency Spectrum ................................................... 3-9
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Figure 3-9:
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Typical Sarsat SARR-1 1544.5 MHz Observed Downlink Signal .................... 3-10
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Figure 3-10: Sarsat SARR Transmitter Spurious Emission Limits ........................................ 3-11
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Figure 3-11: Sarsat SARR-2 Functional Diagram .................................................................. 3-12
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Figure 3-12: Sarsat SARR-2 1544.5 MHz Transmitter Functional Diagram ......................... 3-14
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Figure 3-13: Sarsat SARR-2 Baseband Frequency Spectrum ................................................. 3-14
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Figure 3-14: Typical Sarsat SARR-2 1544.5 MHz Observed Downlink Signal .................... 3-15
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Figure 4-1:
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Cospas SARP-2 Receiver Processor Functional Diagram ................................... 4-2
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Figure 4-2:
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Cospas SARP-2 Frame Formatter Functional Diagram ....................................... 4-4
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Figure 4-3:
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Example of a Cospas SARP-2 Output Message ................................................... 4-6
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Figure 4-4:
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Cospas SARP-2 Short Message Bit Format ......................................................... 4-6
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Figure 4-5:
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Cospas SARP-2 Long Message Bit Format ......................................................... 4-7
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Figure 4-6:
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Sarsat SARP-2 Functional Diagram ..................................................................... 4-9
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Figure 4-7:
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Example of a Sarsat SARP-2 Output Message .................................................. 4-12
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Figure 4-8:
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Sarsat SARP-2 Short Message Bit Format ......................................................... 4-12
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Figure 4-9:
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Sarsat SARP-2 Long Message Bit Format ......................................................... 4-13
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Figure 4-10: Sarsat SARP-3 Functional Diagram ................................................................... 4-15
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Figure 4-11: Example of a Sarsat SARP-3 Output Message .................................................. 4-18
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Figure 4-12: Sarsat SARP-3 Short Message Bit Format ......................................................... 4-19
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Figure 4-13: Sarsat SARP-3 Long Message Bit Format ......................................................... 4-19
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Figure 4-14: Sarsat SARP-3 House-Keeping (HK) Message Bit Format ............................... 4-20
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Figure 5-1:
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Cospas Antenna System Functional Diagram ...................................................... 5-2
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Figure 5-2:
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Cospas (SARP-2) 406 MHz Receive Antenna (SPA) Gain Pattern ..................... 5-2
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Figure 5-3:
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Cospas (SARP-2) 1544.5 MHz Transmit Antenna (SLA) Gain Pattern .............. 5-3
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Figure 5-4:
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Sarsat-TIROS Antenna System Functional Diagram ........................................... 5-4
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Figure 5-5:
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Sarsat-TIROS 406.05 MHz Receive Antenna (SRA) Gain Pattern ..................... 5-5
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Figure 5-6:
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Sarsat-TIROS SARP Receive Antenna (UDA) Gain Pattern (at receiver input) . 5-6
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Figure 5-7:
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Sarsat-TIROS 1544.5 MHz Transmit Antenna (SLA) Gain Pattern .................... 5-7
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Figure 5-8:
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Sarsat-METOP Antenna System Functional Diagram ......................................... 5-8
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Figure 5-9:
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Sarsat-METOP 406 MHz SARR and SARP Receive Antenna (CRA) ............... 5-9
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Figure 5-10: Sarsat-METOP 1544.5 MHz Transmit Antenna (SLA) Gain Pattern .................. 5-9
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Figure 5-11: Sarsat-NPOESS Antenna System Functional Diagram ..................................... 5-10
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Figure 5-12: Sarsat-NPOESS Receive Antenna Gain Pattern ................................................ 5-11
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Figure 5-13: Sarsat-NPOESS Transmit Antenna Gain Pattern ............................................... 5-11
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LIST OF TABLES
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Table 2.1:
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Cospas and Sarsat Satellites Orbital Parameters .................................................. 2-7
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Table 2.2:
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Functions Provided by Cospas and Sarsat Satellites ............................................ 2-7
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Table 2.3:
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Cospas and Sarsat Input Parameters ..................................................................... 2-8
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Table 2.4:
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Cospas and Sarsat Output Parameters ................................................................ 2-10
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Table 3.1:
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Cospas 1544.5 MHz Transmitter Parameters ....................................................... 3-2
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Table 3.2:
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Sarsat SARR Receiver Parameters ....................................................................... 3-5
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Table 3.3:
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Sarsat SARR-1 1544.5 MHz Transmitter Parameters .......................................... 3-8
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Table 3.4:
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Sarsat SARR-2 1544.5 MHz Transmitter Parameters ........................................ 3-13
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Table 4.1:
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Cospas SARP-2 Parameters ................................................................................. 4-2
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Table 4.2:
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Sarsat SARP-2 Parameters ................................................................................... 4-8
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Table 4.3:
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Sarsat SARP-3 Parameters ................................................................................. 4-14
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Table B-1:
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Cospas Sarsat LEOSAR Frequencies .................................................................. B-2
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1-1
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1.
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INTRODUCTION
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The Cospas-Sarsat space segment consists of the Cospas and Sarsat satellites and their respective
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search and rescue (SAR) payloads. The SAR payload consists of the SAR repeaters (SARR), SAR
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processors (SARP) and SAR antennas. The Cospas satellites and SAR payloads are provided by
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Russia. The Sarsat satellites and SAR antennas are provided by USA and Europe. The Sarsat
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SARR and SARP are provided by Canada and France respectively.
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Purpose
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The purpose of this document is to describe the performance parameters of each generation of the
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Cospas and Sarsat payloads and of the downlink signals for nominal operational satellites. This
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document is intended to be used to ensure the interoperability of the Cospas and Sarsat satellites
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and to sufficiently define the downlink to ensure compatible design of LUTs. This document is
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not intended to be used as a specification for the procurement of hardware for the space segment.
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Scope
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This document presents the technical definition and parameters of the Cospas-Sarsat space
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segment. It is divided into the following sections, where part 1 of each section covers Cospas
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payloads and part 2 covers Sarsat payloads:
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section 2 describes the Cospas and Sarsat payloads and the interoperability
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parameters;
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section 3 gives the technical parameters of all repeaters;
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section 4 gives the technical parameters of all processors; and
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section 5 gives the technical parameters of all antennas.
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Reference Documents
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C/S G.003 : Introduction to the Cospas-Sarsat System;
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C/S S.011 : Cospas-Sarsat Glossary;
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C/S T.001 : Specification for Cospas-Sarsat 406 MHz Distress Beacons;
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C/S T.002 : Cospas-Sarsat LEOLUT Performance Specification and Design
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Guidelines; and
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C/S T.006 : Cospas-Sarsat Orbitography Network Specification.
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1-2
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Figure 1-1
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Illustration of Cospas and Sarsat LEOSAR Satellites
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Note: Under nominal operating conditions, the Cospas-Sarsat LEOSAR Space Segment
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consists of four satellites, two Cospas and two Sarsat, in near-polar orbit.
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- END OF SECTION 1 -
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2-1
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2.
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COSPAS-SARSAT PARAMETERS
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The payloads and interoperability parameters for the Cospas-Sarsat space segment are summarised
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in this section.
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Cospas-Sarsat Payloads
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2.1.1
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Cospas-Sarsat Payload Summary
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The Cospas payload is composed of:
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a SAR repeater (SARR);
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a SAR processor (SARP); and
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uplink and downlink antennas.
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The SARR provides local mode coverage for the 406 MHz band.
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The SARP provides both local mode and global mode coverage for the 406 MHz band. Cospas
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satellites have an improved SARP with memory (SARP-2). Processed data is transmitted to the
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ground stations via the downlink transmitter.
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Cospas SARR and SARP are described in sections 3.1 and 4.1 respectively. Processed data is
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transmitted to the ground stations via the downlink transmitter.
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Antenna parameters are given in sub-section 5.1.
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2.1.2
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Cospas Payload System Functional Diagram
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The Cospas payload system functional diagram is shown in Figure 2.1. The downlink signal from
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the SAR L-Band transmit Antenna (SLA) can be detected by any Cospas-Sarsat Local User
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Terminal in the LEOSAR satellite system (LEOLUT).
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2-2
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Figure 2-1:
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Cospas-Sarsat System Functional Diagram
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Sarsat Payload
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SARSAT payload descriptions in this document cover payloads on-board TIROS, METOP and
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the future SIDAR satellites.
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The first generation of SAR Repeaters (SARR-1) is currently in service on TIROS and METOP
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satellites. The second generation of SAR Repeaters (SARR-2) will be on-board any future Sarsat-
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LEOSAR satellites and has been designed with the PDS channel exclusively.
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2-3
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The second generation of SAR Processors (SARP-2) is in service on TIROS satellites (Sarsat-7 to
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Sarsat-10). The third generation of SAR Processors (SARP-3) is in service on METOP-A (Sarsat-
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11), the last TIROS satellite (Sarsat-12), METOP-B (Sarsat-13) and any future Sarsat-LEOSAR
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satellites.
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2.2.1
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Sarsat Payload Summary
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The Sarsat payload is composed of:
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a SAR repeater (SARR);
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a SAR processor (SARP); and
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uplink and downlink antennas.
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The SARR provides local mode coverage for the 406 MHz band and its parameters are given in
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sub-section 3.2 for SARR-1 and PDS only coverage as given in sub-section 3.3 for SARR-2.
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The SARP provides both local mode and global mode coverage for the 406 MHz band. Sarsat
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satellites may have one of two possible SARP configurations installed: SARP-2 or SARP-3. These
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processors are described in sub-sections 4.2.1 and 4.2.2 respectively. Processed data is transmitted
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to the ground stations by the repeater downlink transmitter.
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Antenna parameters for the payload are given in sections 5.2, 5.3 and 5.4 for the TIROS, METOP
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and SIDAR satellites respectively.
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2.2.2
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Sarsat Payload System Functional Diagram
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As shown on the Sarsat payload functional diagram in Figures 2.2, 2.3 and 2.4, the 2.4 kbps
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digital data is routed directly to the SARR.
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2-4
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Figure 2-2:
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Sarsat-TIROS Payload and Spacecraft Interface Functional Diagram with
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SARR-1 and SARP-2 or SARP-3
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2-5
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Figure 2-3:
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Sarsat-METOP Payload and Spacecraft Interface Functional Diagram with
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SARR-1 and SARP-3
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2-6
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Figure 2-4:
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Sarsat Payload and Spacecraft Interface Functional Diagram with SARR-2
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and SARP-3
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Interoperability Parameters
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2.3.1
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Orbit Parameters
|
||
Basic orbital parameters for Cospas and Sarsat satellites are listed in Table 2.1. Each
|
||
satellite is in a different orbital plane.
|
||
|
||
|
||
|
||
|
||
|
||
2-7
|
||
|
||
Table 2.1:
|
||
Cospas and Sarsat Satellites Orbital Parameters
|
||
Parameters
|
||
Unit
|
||
Cospas on
|
||
Meteor-M
|
||
Sarsat on
|
||
TIROS
|
||
Sarsat on
|
||
METOP
|
||
Orbit Type
|
||
N/A
|
||
Circular, Sun-
|
||
Synchronous,
|
||
Near-Polar
|
||
Circular,
|
||
Sun-Synchronous
|
||
Circular,
|
||
Sun-Synchronous
|
||
Altitude
|
||
km
|
||
|
||
(mean value)
|
||
833 to 870
|
||
800 to 850
|
||
Inclination
|
||
Deg
|
||
98.85
|
||
98.7 to 98.86
|
||
98.7
|
||
Period
|
||
min
|
||
101.41
|
||
101.35 to 102.12
|
||
100 to 101.7
|
||
Eccentricity
|
||
N/A
|
||
0.00124
|
||
<0.001
|
||
0.001165
|
||
2.3.2
|
||
Input Parameters
|
||
Table 2.2 lists the functions that are provided by each type of satellite and identifies where they are
|
||
described within this document.
|
||
Table 2.2:
|
||
Functions Provided by Cospas and Sarsat Satellites
|
||
Functions
|
||
Cospas
|
||
Sarsat
|
||
406 MHz Repeater
|
||
Section 3.1
|
||
Section 3.2 (SARR-1)
|
||
Section 3.3 (SARR-2)
|
||
406 MHz Processor
|
||
Section 4.1
|
||
Section 4.2
|
||
Table 2.3 lists input parameters for individual functions provided by the satellites.
|
||
|
||
2-8
|
||
|
||
Table 2.3:
|
||
Cospas and Sarsat Input Parameters
|
||
Parameters
|
||
Unit
|
||
Cospas
|
||
Sarsat
|
||
406 MHz Repeater:
|
||
Centre Frequency
|
||
MHz
|
||
406.05
|
||
406.05 (See note 4)
|
||
1 dB Bandwidth
|
||
kHz
|
||
80.0
|
||
80.0 (See note 4)
|
||
Receiver Noise Temperature
|
||
K
|
||
|
||
350 (See note 4)
|
||
S/C Antenna Polarisation
|
||
N/A
|
||
RHCP
|
||
RHCP (See note 4)
|
||
Nominal Background Noise
|
||
K
|
||
N/A
|
||
1000 (See note 4)
|
||
406 MHz SARP Processor:
|
||
Centre Frequency
|
||
MHz
|
||
See Note 1
|
||
See Notes 2 and 3
|
||
1 dB Bandwidth
|
||
kHz
|
||
See Note 1
|
||
See Notes 2 and 3
|
||
Receiver Noise Temperature
|
||
K
|
||
|
||
|
||
Input Signal from Beacon
|
||
a. Power Flux Density:
|
||
(Nominal orbit) Maximum:
|
||
Nominal:
|
||
b. Polarisation:
|
||
dBW/m2
|
||
N/A
|
||
-121.4
|
||
-142.4
|
||
Linear/RHCP
|
||
-120.0
|
||
-141.0
|
||
Linear/RHCP
|
||
S/C Antenna Polarisation
|
||
N/A
|
||
RHCP
|
||
Nominal Background Noise
|
||
K
|
||
|
||
Note 1:
|
||
SARP-2 allows selection of three different centre frequencies and bandwidths, as
|
||
listed in Table 4.1.
|
||
Note 2:
|
||
SARP-2 allows selection of three different centre frequencies and bandwidths, as
|
||
listed in Tables 4.2 and 4.3.
|
||
Note 3:
|
||
SARP-3 has a fixed bandwidth of 80 kHz centered at 406.050 MHz.
|
||
Note 4:
|
||
SARR-1 only.
|
||
2.3.3
|
||
Output Parameters
|
||
Table 2.4 provides downlink signal parameters for each type of satellite. The modulation index
|
||
given in the table for each channel is the Root-Mean-Square (RMS) value of the carrier phase
|
||
deviation due to that channel. The composite modulation index (RMS) is equal to the square root
|
||
of the sum of the squares of the individual channel modulation indices. The RMS values are
|
||
related to other common methods of measurement as follows.
|
||
|
||
2-9
|
||
|
||
For the Processed Data Stream (PDS) digital channel, the full excursion of the
|
||
phase deviation, also called the peak-to-peak value, is two times the RMS value.
|
||
The peak value equals the RMS value (i.e. signal is basically a square wave).
|
||
For an analogue channel, when a single unmodulated carrier is present at a level
|
||
sufficient to suppress the noise, the peak value of the deviation is
|
||
approximately1.414 times the RMS value (i.e. signal is basically a sine wave).
|
||
2.3.4
|
||
Biphase-L Data Encoding
|
||
A biphase-L data encoding scheme is used in the downlink for the processed 406 MHz data from
|
||
processors. It is shown in Figure 2.5.
|
||
Figure 2-5:
|
||
Processed Data Encoding Scheme
|
||
Data
|
||
Bits
|
||
|
||
|
||
NRZ-L
|
||
+
|
||
Phase
|
||
|
||
|
||
Notes:
|
||
Biphase-L is defined as a transition occurring at the centre of every bit period.
|
||
Symbol "1" is transmitted as:
|
||
"+ phase": the first part of the bit
|
||
"- phase": the second part of the bit; and
|
||
Symbol "0" is transmitted as:
|
||
"- phase": the first part of the bit
|
||
"+ phase": the second part of the bit
|
||
|
||
|
||
|
||
|
||
|
||
2-10
|
||
|
||
Table 2.4:
|
||
Cospas and Sarsat Output Parameters
|
||
Parameter
|
||
Unit
|
||
Cospas
|
||
Sarsat SARR-1
|
||
Sarsat SARR-2
|
||
Transmitted Signal
|
||
Centre Frequency
|
||
MHz
|
||
1544.5
|
||
Nominal Power Output of Transmitter
|
||
W
|
||
4.0
|
||
7.2
|
||
4.0 EOL min
|
||
Phase Jitter (in 50 Hz Bandwidth)
|
||
o (RMS)
|
||
≤ 10
|
||
Occupied Bandwidth 1 (including Doppler)
|
||
kHz
|
||
≤ 800
|
||
Modulation Type
|
||
Linear Phase Modulation
|
||
Nominal Composite Mod. Index
|
||
rad (RMS)
|
||
0.69 to 0.87
|
||
0.70 ± 10%
|
||
0.347 to 0.476
|
||
406.05 MHz Repeater Channel Baseband
|
||
Centre Frequency
|
||
kHz
|
||
75.0
|
||
170.0
|
||
N/A
|
||
Frequency Translation
|
||
N/A
|
||
Uninverted
|
||
Uninverted
|
||
N/A
|
||
Nominal Modulation Index
|
||
rad (RMS)
|
||
0.63 to 0.75
|
||
0.58 ± 10 %
|
||
N/A
|
||
1 dB Bandwidth
|
||
kHz
|
||
|
||
|
||
N/A
|
||
PDS Channel
|
||
Bit Rate
|
||
bps
|
||
2400 ± 0.1%
|
||
2400±0.5%
|
||
Nominal Modulation Index
|
||
rad (RMS)
|
||
0.28 to 0.44
|
||
0.39 ± 10%
|
||
0.347 to 0.476
|
||
Data Encoding (see Figure 2.3)
|
||
N/A
|
||
Biphase-L
|
||
Doppler Measurement Accuracy 2
|
||
Hz (RMS)
|
||
≤ 0.35
|
||
Time Tagging Accuracy 3
|
||
ms
|
||
< 10
|
||
Frequency Measurement Period
|
||
ms
|
||
|
||
|
||
Prob. of Good Signal Processing
|
||
N/A
|
||
> 0.99
|
||
Note 1: The occupied bandwidth, defined by ITU Radio Regulation no. S1.153, remains within the 1,000 kHz allocated by
|
||
the ITU in normal operating conditions.
|
||
Note 2: Both payloads are accurate and stable such that the value of the received frequency at the spacecraft can be
|
||
determined to the indicated accuracy from the data received by the LUT and from equations provided in section 4.
|
||
Note 3: The Cospas satellites have an on-board clock providing absolute time which is maintained to the required accuracy.
|
||
The SARP-2 and SARP-3 instruments on Sarsat satellites do not use an onboard absolute time clock. The absolute
|
||
time tagging may be calculated by the ground stations using the on-board relative time scale and the time calibration
|
||
(TCAL) routinely provided by the FMCC.
|
||
- END OF SECTION 2 -
|
||
|
||
3-1
|
||
|
||
3.
|
||
COSPAS-SARSAT REPEATERS
|
||
Cospas Repater
|
||
As shown in Figure 3.1, the Cospas SARR is redundantly configured and consists of the following
|
||
units:
|
||
two 4.0 W phase modulated L-band transmitters; and
|
||
two Power, Telemetry and Command (PTC) units.
|
||
Redundant units (A side and B side) are selected by commands from the ground which are
|
||
processed by the PTC. The PTC also generates necessary voltages for the repeater system and
|
||
contains interfaces to the spacecraft for all repeater telemetry and command channels.
|
||
Figure 3-1:
|
||
Cospas Repeater Functional Diagram
|
||
A functional diagram of the Cospas transmitter is given in Figure 3.2. It employs a temperature
|
||
controlled crystal oscillator. The linear modulator operates at a frequency of 386.125 MHz. After
|
||
modulation, the output frequency is multiplied by 4 and the final amplification takes place on the
|
||
1544.5 MHz frequency.
|
||
Before entering the linear phase modulator, modulation signals are amplified by a wideband linear
|
||
amplifier. There is a two-level limiter in this amplifier, which prevents the instantaneous value of
|
||
the summed modulating signal to exceed a certain level.
|
||
|
||
|
||
|
||
|
||
|
||
3-2
|
||
|
||
The modulation index adjustment is achieved by means of change of signal modulating voltage,
|
||
which is subsequently passed to the input of the wideband linear amplifier.
|
||
The Cospas 1544.5 MHz transmitter parameters given in Table 3.1 are in addition to those given
|
||
in section 2. The downlink signal observed on the ground is illustrated in Figure 3.3.
|
||
Table 3.1:
|
||
Cospas 1544.5 MHz Transmitter Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Downlink Baseband Spectrum
|
||
N/A
|
||
Figure 3.3
|
||
Incidental AM
|
||
%
|
||
≤ 5
|
||
Spurious Output Level
|
||
dBW
|
||
≤ -60
|
||
Frequency Stability
|
||
Long term (5 yr.):
|
||
Medium term (15 min.):
|
||
Short term (0.1 sec.):
|
||
kHz
|
||
N/A
|
||
N/A
|
||
± 1.5
|
||
5 x 10 -8
|
||
5 x 10 -10
|
||
Maximum Modulation Index Level:
|
||
PDS:
|
||
Composite:
|
||
rad. (peak)
|
||
rad. (peak)
|
||
0.92 (max. setting)
|
||
2.80 (hard limiter)
|
||
Amplitude Ripple
|
||
dB
|
||
≤ 2.5
|
||
Figure 3-2:
|
||
Cospas 1544.5 MHz Transmitter Functional Diagram
|
||
\
|
||
Relative Signal Power (dB)
|
||
|
||
|
||
|
||
3-3
|
||
|
||
Figure 3-3:
|
||
Typical Cospas 1544.5 MHz Observed Downlink Signal
|
||
Frequency (kHz) - relative to downlink carrier centre frequency
|
||
Sarsat Repeater SARR-1 (Sarsat-13 and earlier)
|
||
As shown in Figure 3.4, the Sarsat SARR is redundantly configured and consists of the following
|
||
units:
|
||
two dual-conversion 406.05 MHz receivers (Sarsat-1,-2,-3 and -4 have only one
|
||
406.05 MHz receiver mounted on the A side);
|
||
two 7.2 W phase modulated L-band transmitters; and
|
||
two Power, Telemetry and Command units.
|
||
Redundant units (A side and B side) are selected by commands from the ground which are
|
||
processed by the PTC. The PTC also generates necessary voltages for the repeater system and
|
||
contains interfaces to the spacecraft for all repeater telemetry and command channels.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
3-4
|
||
|
||
Figure 3-4:
|
||
Sarsat SARR-1 Functional Diagram
|
||
Transmitter - A Side
|
||
Transmitter - B Side
|
||
1544.5 MHz Output
|
||
406.05 MHz Receiver - A Side
|
||
Local Oscillator
|
||
406.05 MHz Receiver - B Side
|
||
Local Oscillator
|
||
Power Telemetry and
|
||
Command A - Side
|
||
Power Telemetry and
|
||
Command B - Side
|
||
RF
|
||
Switch
|
||
RF
|
||
Switch
|
||
Filter
|
||
406 MHz Input
|
||
2.4 kbps from
|
||
SARP
|
||
To B Transmitter
|
||
To B Transmitter
|
||
170 kHz Baseband
|
||
170 kHz BB
|
||
2.4 kbps
|
||
2.4 kbps
|
||
Power Telemetry and
|
||
Command To Spacecraft
|
||
3.2.1
|
||
Sarsat SARR-1 Receivers
|
||
As shown in Figure 3.5, the 406 MHz receiver contains AGC and provides two outputs to drive
|
||
the two transmitters. The Sarsat SARR receiver parameters given in Table 3.2 are in addition to
|
||
those given in section 2.
|
||
|
||
3-5
|
||
|
||
Table 3.2:
|
||
Sarsat SARR Receiver Parameters
|
||
Parameters
|
||
Unit
|
||
Values for
|
||
406.05 MHz
|
||
Receiver
|
||
Nominal Input Level1
|
||
dBW
|
||
|
||
Maximum Input Level
|
||
dBW
|
||
|
||
Dynamic Range
|
||
dBW
|
||
-164.3 to -137.2
|
||
Linearity
|
||
N/A
|
||
Note 2
|
||
Group Delay Slope
|
||
µs/kHz
|
||
|
||
Image Rejection
|
||
dB
|
||
|
||
AGC Time Constant
|
||
ms
|
||
10 - 85
|
||
AGC Dynamic Range3
|
||
dB
|
||
> 50
|
||
Transient Recovery Time
|
||
ms
|
||
< 2
|
||
Frequency Stability
|
||
Long term (2 yr.):
|
||
Medium term (15 min.):
|
||
Short term (1 sec.):
|
||
N/A
|
||
N/A
|
||
N/A
|
||
1 x 10-6
|
||
1 x 10-10
|
||
1 x 10-10
|
||
Note 1: Nominal input level for 406 MHz is defined as the nominal noise of 1000 K plus ten simultaneous
|
||
signals, each of -147.6 dBW.
|
||
Note 2: With receivers in AGC mode and with nominal level settings, two out-of-band (for bandwidths
|
||
in Figure 3.8) signals of -92 dBW at the receiver input, or two inband signals of -110 dBW, do
|
||
not produce intermodulation products within the same baseband exceeding an output level of -
|
||
170 dBW with respect to the receiver input.
|
||
Note 3: The peak modulation index limit of each repeater band is set such that any single inband signal
|
||
of up to -110 dBW will not cause the composite modulation index limit to be reached before the
|
||
AGC reduces the receiver output level back to nominal.
|
||
|
||
3-6
|
||
|
||
Figure 3-5:
|
||
Sarsat SARR Receiver Functional Diagram
|
||
Medium term frequency stability (over a 15 minute period) for the receiver is given as:
|
||
Nominal Temperature:
|
||
Mean Slope:
|
||
≤1 x 10-10/minute
|
||
Residual Noise:
|
||
≤3 x 10-10
|
||
Full Temperature Range:
|
||
Mean Slope:
|
||
≤1 x 10-9/minute
|
||
Residual Noise:
|
||
≤3 x 10-9
|
||
The baseband filtering characteristic for the 406 MHz channel is given in Figure 3.6. Signals at
|
||
frequencies indicated are attenuated by the corresponding amount with respect to the 0 dB level.
|
||
Within this band, the receiver provides gain for those frequencies which fall within the band as
|
||
specified in Table 2.4.
|
||
Inband interfering signals in the band do not induce unwanted signals in the band exceeding -
|
||
175 dBW referred to the input and do not cause the modulation index to exceed the maximum
|
||
level.
|
||
|
||
|
||
|
||
3-7
|
||
|
||
Figure 3-6:
|
||
Sarsat SARR Receiver Bandpass Characteristics
|
||
3.2.2
|
||
Sarsat SARR-1 1544.5 MHz Transmitter
|
||
As shown in Figure 3.7, each one of the transmitters has four inputs; one for each of the
|
||
two 406 MHz receivers, one for the PDS channel and one spare.
|
||
Sarsat transmitter parameters given in Table 3.3 below are in addition to parameters given in
|
||
section 2. The downlink baseband frequency spectrum and an example of the signal observed on
|
||
the ground are given in Figures 3.8 and 3.9.
|
||
When the receiver input is illuminated by a sinusoidal signal at the maximum frequency and level,
|
||
and by the processed data stream, no single discrete sideband is produced which exceed the limits
|
||
shown in Figure 3.10. Noise-like emissions do not exceed the levels specified in Figure 3.10.
|
||
With a receiver in AGC mode and nominal level setting, spurious output in the demodulated
|
||
downlink spectrum do not exceed -175 dB with respect to a receiver input.
|
||
|
||
|
||
|
||
3-8
|
||
|
||
Table 3.3:
|
||
Sarsat SARR-1 1544.5 MHz Transmitter Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Downlink Baseband Spectrum
|
||
N/A
|
||
Figures 3.8 and 3.9
|
||
Incidental AM
|
||
%
|
||
≤5
|
||
Spurious Output Level
|
||
dBW
|
||
Figure 3.10
|
||
Frequency Stability
|
||
Long term (2 yr.):
|
||
Medium term (15 min.):
|
||
Short term (1 sec.):
|
||
kHz
|
||
N/A
|
||
N/A
|
||
± 3.2
|
||
≤ 1 x 10-10
|
||
≤ 1 x 10-10
|
||
Maximum Modulation Index Level:
|
||
406.05:
|
||
PDS:
|
||
Composite:
|
||
rad. (peak)
|
||
rad. (peak)
|
||
rad. (peak)
|
||
1.30 (hard limiter)
|
||
0.39 (max. setting)
|
||
2.10 (hard limiter)
|
||
Amplitude Ripple
|
||
dB
|
||
≤ 2.5
|
||
Figure 3-7:
|
||
Sarsat SARR-1 1544.5 MHz Transmitter Functional Diagram
|
||
Multiplier
|
||
Oscillator
|
||
Phase
|
||
Modulator
|
||
Filter
|
||
Filter
|
||
IF
|
||
RF
|
||
1544.5 MHz Output
|
||
Baseband Summer
|
||
406 MHz Receiver
|
||
2.4 kbps PDS
|
||
406 MHz Receiver
|
||
A Side:
|
||
Basebands
|
||
B Side:
|
||
Basebands
|
||
SPARE
|
||
|
||
3-9
|
||
|
||
Figure 3-8:
|
||
Sarsat SARR-1 Baseband Frequency Spectrum
|
||
|
||
|
||
|
||
3-10
|
||
|
||
Figure 3-9:
|
||
Typical Sarsat SARR-1 1544.5 MHz Observed Downlink Signal
|
||
|
||
|
||
|
||
3-11
|
||
|
||
Figure 3-10: Sarsat SARR Transmitter Spurious Emission Limits
|
||
Sarsat Repeater SARR-2 (Sarsat-14 and after)
|
||
As shown in Figure 3.11, the Sarsat SARR-2 consists of the following modules:
|
||
one Power, Telemetry and Command (PT&C) module;
|
||
one Frequency Generator module;
|
||
one SAW filter; and
|
||
one phase modulated L-band transmitter module.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
3-12
|
||
|
||
3.3.1
|
||
SARR-2 Power, Telemetry and Command
|
||
The PT&C generates necessary voltages for the repeater system and contains the interfaces to the
|
||
spacecraft for the repeater telemetry and command channels.
|
||
Figure 3-11: Sarsat SARR-2 Functional Diagram
|
||
3.3.2
|
||
SARR-2 Frequency Generator
|
||
In SARR-2, a portion of the transmitter has been separated into a module of its own. The module
|
||
consists of a stable 10MHz reference and synthesizer to generate the L-Band (1544.5 MHz) carrier.
|
||
This L-Band LO is then supplied to the phase modulator in the Transmit module where the
|
||
baseband signal is modulated onto the carrier. The Sarsat SARR-2 transmitter functional diagram
|
||
is presented in Figure 3.12 and includes the functionality in the frequency generator module.
|
||
3.3.3
|
||
SARR-2 SAW FILTER
|
||
The SAW filter is placed between the frequency generator and the transmitter modules on the
|
||
LO/Carrier signal path. The SAW filter is a band-pass filter used to reduce the out of band spurious
|
||
and noise emission levels from the frequency generator module.
|
||
|
||
|
||
|
||
3-13
|
||
|
||
3.3.4
|
||
Sarsat SARR-2 1544.5 MHz Transmitter
|
||
The Sarsat SARR-2 transmitter Functional Diagram is presented in Figure 3.12. The transmitter
|
||
module has two inputs; one for the PDS channel and one for the L-Band LO input from the SAW
|
||
filter.
|
||
Sarsat SARR-2 transmitter parameters given in Table 3.4 below are in addition to parameters given
|
||
in section 2. The downlink baseband frequency spectrum and an example of the signal observed
|
||
on the ground are given in Figures 3.13 and 3.14.
|
||
When the processed data stream is present, no single discrete sideband is produced which exceeds
|
||
the limits shown in Figure 3.10. Noise-like emissions do not exceed the levels specified in Figure
|
||
3.10, excluding the near/in-band frequency range of 1544.5 ±10 kHz, and the range Fc ±10 kHz
|
||
to Fc ±100 kHz. Noise-like emissions do not exceed
|
||
-60dBW/Hz for the range Fc ±10 kHz to Fc ±100 kHz.
|
||
Table 3.4:
|
||
Sarsat SARR-2 1544.5 MHz Transmitter Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Downlink Baseband Spectrum
|
||
N/A
|
||
Figures 3.13 and 3.14
|
||
Incidental AM
|
||
%
|
||
≤5
|
||
Spurious Output Level
|
||
dBW
|
||
Figure 3.10 with exceptions for
|
||
noise- like emissions stated above
|
||
Frequency Stability
|
||
Long term (7 yr.):
|
||
Medium term (15 min.):
|
||
Short term (1 sec.):
|
||
kHz
|
||
N/A
|
||
N/A
|
||
± 3.2
|
||
≤ 1 x 10-10
|
||
≤ 1 x 10-10
|
||
Maximum Modulation Index Level:
|
||
rad. (peak)
|
||
0.7 (hard limiter)
|
||
Amplitude Ripple
|
||
dB (peak to peak)
|
||
≤ 2.5
|
||
|
||
3-14
|
||
|
||
Figure 3-12: Sarsat SARR-2 1544.5 MHz Transmitter Functional Diagram
|
||
Figure 3-13: Sarsat SARR-2 Baseband Frequency Spectrum
|
||
|
||
|
||
|
||
|
||
|
||
3-15
|
||
|
||
Figure 3-14: Typical Sarsat SARR-2 1544.5 MHz Observed Downlink Signal
|
||
- END OF SECTION 3 -
|
||
Relative
|
||
Signal
|
||
Power (dB)
|
||
Frequency (kHz) - relative to downlink carrier centre
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-1
|
||
|
||
4.
|
||
COSPAS-SARSAT SARPS
|
||
Cospas SARP
|
||
The Cospas SARP is composed of a Receiver Processor, a Frame Formatter (FF) and a memory unit.
|
||
Each Cospas SARP is redundantly configured.
|
||
The following satellites contain the indicated SARPs which are described in this document:
|
||
Cospas-14 and follow on: SARP-2
|
||
Cospas satellites C-1 to C-10 have been gradually decommissioned from service. Cospas satellites C-11,
|
||
C-12 and C-13 have not been commissioned.
|
||
The SARP-2 has improved performance in system capacity, bandwidth and protection against interferers.
|
||
Both long and short messages are supported by this processor.
|
||
Cospas SARP-2 parameters given in Table 4.1 are in addition to those given in section 2.
|
||
4.1.1
|
||
Cospas SARP-2 Receiver Processor
|
||
A functional diagram of the Receiver Processor is shown in Figure 4.1. The Receiver Processor unit is
|
||
composed of the following:
|
||
one dual-conversion receiver;
|
||
one Analog to Digital (A/D) converter;
|
||
one Search Unit;
|
||
three Data Recovery Units (DRUs);
|
||
one Control Unit;
|
||
one Central Processor Unit; and
|
||
Power, Telemetry and Command circuit
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-2
|
||
|
||
Table 4.1:
|
||
Cospas SARP-2 Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Receiver Centre Frequency -
|
||
Mode 1
|
||
(selectable)
|
||
Mode 2
|
||
Mode 3
|
||
MHz
|
||
406.0235
|
||
406.0300
|
||
406.0500
|
||
Receiver Bandwidth (1 dB) -
|
||
Mode 1
|
||
(selectable)
|
||
Mode 2
|
||
Mode 3
|
||
kHz
|
||
|
||
|
||
Receiver Dynamic Range
|
||
dBW
|
||
-161 to -138
|
||
Frequency Stability
|
||
Long-term (5 yr.):
|
||
Short-term (0.1 sec.):
|
||
kHz
|
||
N/A
|
||
± 1.5
|
||
1 x 10-10
|
||
Frequency of sub-carrier (406 MHz signals relay mode)
|
||
kHz
|
||
75.0
|
||
Bit Error Rate1
|
||
N/A
|
||
< 1 x 10-5
|
||
Output Data Rate
|
||
bps
|
||
2,400
|
||
Time Measurement Increment
|
||
ms
|
||
|
||
Ambiguity of Time Tagging
|
||
Hrs
|
||
|
||
Number of DRUs
|
||
N/A
|
||
|
||
Memory Capacity
|
||
messages
|
||
bits
|
||
2,000
|
||
460,800
|
||
Message Types Supported
|
||
N/A
|
||
Short and long
|
||
Note 1: BER applies for signal level of -161 dBW and Receiver Noise Temperature of 600 K.
|
||
Figure 4-1:
|
||
Cospas SARP-2 Receiver Processor Functional Diagram
|
||
|
||
|
||
|
||
4-3
|
||
|
||
The analog output of the receiver is converted into a digital form by the analog to digital converter. The
|
||
search unit performs spectrum analysis to determine frequency
|
||
and amplitude. The spectrum analyser on commands from the ground, can analyze one of the three bands.
|
||
When a signal is detected, the central processor assigns that signal to a DRU. On commands from the
|
||
central processor, the DRU performs signal acquisition and demodulation, and determines the Doppler
|
||
frequency of the received signal.
|
||
In addition to controlling the functioning of the DRUs, the central processor also:
|
||
-
|
||
assigns DRUs to beacon signals;
|
||
-
|
||
checks the performance of the DRUs; and
|
||
-
|
||
performs self-testing.
|
||
-
|
||
This SARP-2 uses a new algorithm to protect the instrument against interferers. It is designed to avoid a
|
||
continuous assignment of DRUs to interferer signals, thus making them available to process beacon
|
||
signals.
|
||
The control unit performs the following functions:
|
||
-
|
||
performance monitoring of the analogue receiver;
|
||
-
|
||
check out of the analogue receiver performance as well as that of the spectrum analyser; and
|
||
-
|
||
self checking.
|
||
4.1.2
|
||
Cospas SARP-2 Frame Formatter
|
||
A functional diagram of the Frame Formatter (FF) is shown in Figure 4.2. The FF accepts all messages
|
||
received from the DRUs and recorded messages are passed continuously to the modulator of the
|
||
transmitter.
|
||
|
||
4-4
|
||
|
||
Figure 4-2:
|
||
Cospas SARP-2 Frame Formatter Functional Diagram
|
||
Main Frame
|
||
Memory 1
|
||
Main Frame
|
||
Memory 2
|
||
Main Frame
|
||
Memory 3
|
||
Processor
|
||
|
||
Processor
|
||
|
||
Output
|
||
Interface
|
||
|
||
Output
|
||
Interface
|
||
|
||
Input
|
||
Interface
|
||
|
||
Input
|
||
Interface
|
||
|
||
Adaptor
|
||
|
||
Adaptor
|
||
|
||
Digital Data
|
||
from Receiver Processor
|
||
Time Code
|
||
Digital Data
|
||
to Transmitter
|
||
Telemetry Data
|
||
4.1.3
|
||
Cospas SARP-2 Output Format
|
||
Beacon messages from the Cospas SARP-2 are transmitted in blocks of 25 words, as shown in the
|
||
example of Figure 4.3.
|
||
Prime format rules are:
|
||
Zero words '000001'(Hex) are inserted at the end of each short message as necessary;
|
||
Word # 00 = always frame sync '42BB1F'(Hex);
|
||
DRU words are sequential and not interleaved; and
|
||
Long and short beacon messages can be mixed.
|
||
Bit formats for each type of message are shown in Figures 4.4 and 4.5. Words contain the following
|
||
information:
|
||
Word 0:
|
||
Sync word 'D60' (Hex) followed by 6 bits as described in the figures and then
|
||
6 bits of level and parity. The 5 bit received level is given by:
|
||
Level (dBW) = -161+L
|
||
where L is the 5-bit level in decimal form.
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-5
|
||
|
||
Word 1:
|
||
The Doppler count is followed by its parity bit. The Doppler frequency is given by:
|
||
where N is the Doppler count in decimal form.
|
||
The frequency at the input of the satellite receiver, Fin, is given by:
|
||
Fin (Hz) = Fd + 406,010,000
|
||
Word 2: The time code followed by its parity bit. It is quantized in steps of 16 ms, synchronised
|
||
with the beginning of the Doppler count and given as:
|
||
Hours (5 bits): Minutes (6 bits) : seconds(6 bits): 16 ms (6 bits)
|
||
The time given is 2hr 59min and 59 sec ahead of UTC
|
||
(i.e. UTC = Cospas time - 2:59:59)
|
||
Words 3 to 5: 72 bits of the beacon message.
|
||
Word 6a: Last 16 bits of beacon short message followed by 8 zeros.
|
||
Word 6b: 24 bits of beacon long message.
|
||
Word 7a: Zero word '000001' (Hex) for short message.
|
||
Word 7b: Last 24 bits of beacon long message.
|
||
Fd (Hz) =
|
||
62,500 N
|
||
|
||
− 35,000
|
||
|
||
4-6
|
||
|
||
Figure 4-3:
|
||
Example of a Cospas SARP-2 Output Message
|
||
Word
|
||
Word Content (Hex)
|
||
|
||
42BB1F
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
Short
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
42BB1F
|
||
Figure 4-4:
|
||
Cospas SARP-2 Short Message Bit Format
|
||
Word
|
||
\#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
pseudo
|
||
DRU
|
||
latest
|
||
RT/PB
|
||
Parity
|
||
level
|
||
Parity
|
||
(12 bits)
|
||
(1b)
|
||
(2b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(5b)
|
||
(1b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
(5)
|
||
(5)
|
||
|
||
Doppler count (23 bits)
|
||
Parity (1 bit) (note 7)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 7)
|
||
hours
|
||
:
|
||
minutes
|
||
:
|
||
seconds
|
||
:
|
||
16 ms
|
||
(5 bits)
|
||
(6 bits)
|
||
(6 bits)
|
||
(6 bits)
|
||
|
||
Format flag (1 bit)(note 6)
|
||
Beacon data (23 bits)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
6a
|
||
Beacon data (16 bits)
|
||
8 0's
|
||
7a
|
||
'zero word' (24 bits) = 000001 (hex)
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-7
|
||
|
||
Figure 4-5:
|
||
Cospas SARP-2 Long Message Bit Format
|
||
Word
|
||
\#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
pseudo
|
||
DRU
|
||
latest
|
||
RT/PB
|
||
Parity
|
||
level
|
||
Parity
|
||
(12 bits)
|
||
(1b)
|
||
(2b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(5b)
|
||
(1b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
(5)
|
||
(5)
|
||
|
||
Doppler count (23 bits)
|
||
Parity (1 bit) (note 7)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 7)
|
||
hours
|
||
:
|
||
minutes
|
||
:
|
||
seconds
|
||
:
|
||
16 ms
|
||
(5 bits)
|
||
(6 bits)
|
||
(6 bits)
|
||
(6 bits)
|
||
|
||
Format flag (1 bit)(note 6)
|
||
Beacon data (23 bits)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
6b
|
||
Beacon data (24 bits)
|
||
7b
|
||
Beacon data (24 bits)
|
||
Notes:
|
||
(1)
|
||
Pseudo-mode is not supported on Cospas satellites, beginning with Cospas-14. The value is defaulted to
|
||
"0".
|
||
(2)
|
||
"01" = DRU1; "10" = DRU2; "11" = DRU3.
|
||
(3)
|
||
"1" = most recent message(playback); "0" = others.
|
||
(4)
|
||
"1" = real time message; "0" = playback message.
|
||
(5)
|
||
Parity bit on previous five bits: "1" = odd number of "1".
|
||
(6)
|
||
Format flag: "1" = long message; "0" = short message.
|
||
(7)
|
||
Parity bit in words 1 and 2:'1' with odd number of '1s' in the 23 bits of the Doppler count or the Time
|
||
code.
|
||
Sarsat SARP
|
||
The following satellites contain the indicated SARPs which are described in this document:
|
||
Sarsat-7: SARP-2
|
||
Sarsat-8: SARP-2
|
||
Sarsat-9: SARP-2
|
||
Sarsat-10: SARP-2
|
||
Sarsat-11: SARP-3
|
||
Sarsat-12: SARP-3
|
||
Sarsat-13: SARP-3
|
||
Sarsat-14: SARP-3
|
||
Sarsat-15: SARP-3
|
||
The SARP instruments on Sarsat satellites Sarsat-1 to Sarsat-6 have been decommissioned from service.
|
||
4.2.1
|
||
Sarsat SARP-2
|
||
The functional diagram of the SARP-2 Processor is shown in Figure 4.6.
|
||
SARP-2 parameters given in Table 4.2 are in addition to those given in section 2.
|
||
|
||
|
||
|
||
4-8
|
||
|
||
Table 4.2:
|
||
Sarsat SARP-2 Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Receiver Centre Frequency -
|
||
Mode 1
|
||
(selectable)
|
||
Mode 2
|
||
Mode 3
|
||
MHz
|
||
406.0235
|
||
406.0300
|
||
406.0500
|
||
Receiver Bandwidth (1 dB) -
|
||
Mode 1
|
||
(selectable)
|
||
Mode 2
|
||
Mode 3
|
||
kHz
|
||
|
||
|
||
Receiver Dynamic Range
|
||
dBW
|
||
-161 to -138
|
||
Bit Error Rate1
|
||
N/A
|
||
< 1 x 10-5
|
||
Output Data Rate
|
||
bps
|
||
|
||
Time Measurement Increment
|
||
ms
|
||
19.1 approx.
|
||
Ambiguity of Time Tagging
|
||
Hrs
|
||
44.5 approx.
|
||
Signal Level Measurement Accuracy2
|
||
dBm
|
||
+/- 2.0
|
||
Signal Level Measurement Quantization
|
||
dBm
|
||
0.5
|
||
Number of DRUs
|
||
N/A
|
||
|
||
Memory Capacity (short
|
||
or long messages)
|
||
messages
|
||
bits
|
||
|
||
400k approx.
|
||
Message Types Supported
|
||
N/A
|
||
Short and long
|
||
Note 1: BER applies for signal level of -161 dBW and Receiver Noise Temperature of 300 K.
|
||
Note 2: 1 to 2% of all signal level measurements provide erroneous information (i.e. the
|
||
minimum allowable value is provided rather than the actual value).
|
||
|
||
4-9
|
||
|
||
Figure 4-6:
|
||
Sarsat SARP-2 Functional Diagram
|
||
2.4 kbps PDS to SARR
|
||
RF Input
|
||
Power
|
||
Supplies
|
||
Telemetry
|
||
Commands
|
||
Frame Formatter and Memory
|
||
Receiver
|
||
Control
|
||
Unit
|
||
DRU 1
|
||
DRU 2
|
||
DRU 3
|
||
Search Unit
|
||
A/D
|
||
4.2.1.1
|
||
Sarsat SARP-2 Receiver Processor
|
||
The SARP-2 instrument has improved performance in system capacity, bandwidth and protection
|
||
against interferers.
|
||
Logic circuits using the Fast Fourier Transform algorithm perform signal searching by making a
|
||
spectrum analysis of the receiver output (determination of frequency and level).
|
||
The receiver is a temperature-compensated, constant-gain receiver.
|
||
This processor uses a new algorithm to protect the instrument against interferers. It is designed to
|
||
avoid a continuous assignment of DRUs to interferer signals, thus making them available to
|
||
process beacon signals. To locate an interferer which has a stable frequency, the Control Unit can
|
||
enable, on command from the ground, any one of the DRUs (but only at a time) to generate
|
||
"pseudo-messages", (i.e. messages which do not have valid identification data, but do have valid
|
||
time/frequency points), which can be specially processed by LUTs to locate interferers. The
|
||
average time between pseudo- messages generated is at least 10 seconds. While the one DRU is in
|
||
this special mode, the other two DRUs continue to process beacon signals as normal.
|
||
|
||
4-10
|
||
|
||
It has three DRUs to improve reliability and capacity of the system. Each DRU comprises a
|
||
phaselock loop with new circuits that are mostly digital, a bit synchroniser using a new digital
|
||
design and a formatter. The capacity of the memory has been
|
||
increased to approximately 400 kbits allowing the storage of up to 2048 messages (long or short
|
||
or pseudo-messages) for global area coverage.
|
||
This instrument's mass memory operates similarly to the SARP-1 memory. The same five
|
||
commands have the same effects.
|
||
The capacity of the memory has been increased to approximately 400 kbits to take into account
|
||
the storage of pseudo-messages when the instrument is used to locate interferers. To simplify the
|
||
hardware associated with the reading of the messages, all messages, short or long, are stored in the
|
||
same number of addresses. A short message is followed by a zero word to occupy the same
|
||
memory space as a long message.
|
||
4.2.1.2 Sarsat SARP-2 Output Format
|
||
Beacon messages from the Sarsat SARP-2 are transmitted in blocks of 25 words as shown in the
|
||
example of Figure 4.7.
|
||
Prime format rules are:
|
||
Zero words '000001'(Hex) are inserted at the end of each short message as
|
||
necessary;
|
||
Word # 00 = always frame sync '42BB1F'(Hex); and
|
||
If read continuous mode is active and if the oldest playback message has just been
|
||
transmitted, a block of eight zero words will precede resumption of playback
|
||
which will start with the first word of the most recently stored message.
|
||
The bit format for both length of message formats are shown in Figures 4.8 and 4.9, where the
|
||
Most Significant Bit (MSB) of Word 0 is transmitted first. All words contain the following
|
||
information:
|
||
Word 0:
|
||
Sync word 'D60' (Hex) followed by 6 bits described in the figure and then the signal
|
||
level. The received level is given by:
|
||
Level (dBm) = 0.564L – 140
|
||
where L is the 6-bit level converted to decimal form
|
||
Word 1:
|
||
The time code is quantized in steps of 's' ms and synchronised with the beginning
|
||
of the Doppler count. The last bit is a parity bit. The quantization is given by:
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-11
|
||
|
||
ms
|
||
19.096
|
||
Hz
|
||
|
||
|
||
F
|
||
|
||
|
||
s
|
||
r
|
||
≈
|
||
=
|
||
=
|
||
where Fr is frequency of oscillator (approx 5 203 205 Hz)
|
||
The UTC time T is given by: T = To + 223ks + s(Md + 1)
|
||
where s ≈ 19.096 ms ( the resolution time of the counter);
|
||
Md = decimal value of the 23-bit on-board time code;
|
||
To = UTC of an arbitrarily chosen reset to zero of the counter; and
|
||
k =
|
||
Number of resets to zero of the counter between time To and time T. The
|
||
value of k is computed in ground processing, for each message, with a
|
||
coarse estimate Te of T as the integer part of:
|
||
(
|
||
)
|
||
T
|
||
T
|
||
s
|
||
e
|
||
o
|
||
−
|
||
±
|
||
|
||
|
||
The coarse estimate Te can be obtained either by processing a time
|
||
calibration beacon message from stored data or from the real time when
|
||
processing local mode data. The time calibration beacon is described in C/S
|
||
T.006.
|
||
Words 2 to 4: 72 bits of the beacon message.
|
||
Word 5a:
|
||
Last 15 bits of beacon short message data followed by 9 zeros. Word 5b: 24 bits
|
||
of beacon long message data.
|
||
Word 6a and 7b: 23-bit Doppler word with parity. The frequency at the input of the satellite
|
||
receiver, Fin, is given by:
|
||
Fin = Fr (( aN) + b ) Hz
|
||
where
|
||
;
|
||
|
||
|
||
3.05664845
|
||
|
||
|
||
a
|
||
|
||
|
||
×
|
||
≈
|
||
×
|
||
=
|
||
b = 78 + 1
|
||
|
||
x 624
|
||
26 +
|
||
+
|
||
≈
|
||
|
||
|
||
78 02564104137
|
||
|
||
.
|
||
.
|
||
;
|
||
Fr ≈5 203 205 Hz; and
|
||
N = Doppler count in decimal form.
|
||
Word 6b:
|
||
Last 23 bits of beacon long message data followed by one zero.
|
||
Word 7a:
|
||
Zero word "000001 (Hex)".
|
||
For pseudo-messages, the 13th bit of Word 0 is set. Pseudo-messages are short messages, having
|
||
the bit format shown in Figure 4.8, but the beacon data is replaced by:
|
||
|
||
4-12
|
||
|
||
Words 2, 3 and 4: 0000 1111 0000 1111 0000 1111
|
||
Word 5:
|
||
0000 1111 0000 1110 0000 0000
|
||
Note: Fr is the frequency of the SARP Ultra Stable Oscillator. LEOLUTs should use a recent
|
||
estimate of the USO frequency, as provided in a recent SARP calibration message (SIT
|
||
415) or as calculated by the LEOLUT, for determining the time and frequency of the
|
||
beacon burst.
|
||
To is the UTC of an arbitrarily chosen time of reset to zero of the SARP time counter. For
|
||
calculating the time of a beacon burst, LEOLUTs should use a recent To value as provided in a
|
||
recent SIT 415 message or as calculated by the LEOLUT.
|
||
Figure 4-7:
|
||
Example of a Sarsat SARP-2 Output Message
|
||
Word Word Content (Hex)
|
||
|
||
42BB1F
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Short
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
|
||
D60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
42BB1F
|
||
|
||
D60…
|
||
|
||
……
|
||
Figure 4-8:
|
||
Sarsat SARP-2 Short Message Bit Format
|
||
|
||
4-13
|
||
|
||
Word
|
||
\#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
pseudo
|
||
DRU
|
||
Format
|
||
latest
|
||
RT/PB
|
||
level
|
||
(12 bits)
|
||
(1b)
|
||
(2b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(6b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
(5)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 6)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
5a
|
||
Beacon data (15 bits)
|
||
9 0's
|
||
6a
|
||
Doppler word (23 bits)
|
||
Parity (1 bit) (note 6)
|
||
7a
|
||
"zero word" (24 bits) = 000001 (hex)
|
||
Figure 4-9:
|
||
Sarsat SARP-2 Long Message Bit Format
|
||
Word
|
||
\#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
pseudo
|
||
DRU
|
||
Format
|
||
latest
|
||
RT/PB
|
||
level
|
||
(12 bits)
|
||
(1b)
|
||
(2b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(6b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
(5)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 6)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
5b
|
||
Beacon data (24 bits)
|
||
6b
|
||
Beacon data (23 bits)
|
||
zero bit (1 bit)
|
||
7b
|
||
Doppler word (23 bits)
|
||
Parity (1 bit) (note 6)
|
||
Notes :
|
||
(1)
|
||
"1" = pseudo-message; "0" = beacon message.
|
||
(2)
|
||
"01" = DRU1; "10" = DRU2; "11" = DRU3.
|
||
(3)
|
||
"1" = long message; "0" = short message.
|
||
(4)
|
||
"1" = most recent message(playback); "0" = others.
|
||
(5)
|
||
"1" = real time message; "0" = playback message.
|
||
(6)
|
||
Parity: "1" = odd number of "1s" in the 23-bit time code or the 23-bit Doppler code.
|
||
|
||
4-14
|
||
|
||
4.2.2
|
||
Sarsat SARP-3
|
||
The functional diagram of the SARP 3 Processor is shown in Figure 4.10.
|
||
SARP-3 parameters given in Table 4.3 are in addition to those given in section 2.
|
||
Table 4.3:
|
||
Sarsat SARP-3 Parameters
|
||
Parameters
|
||
Unit
|
||
Values
|
||
Receiver Centre Frequency
|
||
MHz
|
||
406.0500
|
||
Receiver Bandwidth (1 dB)
|
||
kHz
|
||
|
||
Receiver Dynamic Range
|
||
dBW
|
||
-164 to -138
|
||
Bit Error Rate (See Note 1)
|
||
N/A
|
||
< 1 x 10-5
|
||
Output Data Rate
|
||
bps
|
||
2399.8
|
||
Time Measurement Increment
|
||
ms
|
||
20 approx.
|
||
Ambiguity of Time Tagging
|
||
Hrs
|
||
44.5 approx.
|
||
Signal Level Measurement Accuracy
|
||
dBm
|
||
TBD
|
||
Signal Level Measurement Quantization
|
||
dBm
|
||
TBD
|
||
Number of DRUs
|
||
N/A
|
||
|
||
Memory Capacity (short
|
||
or long messages)
|
||
messages
|
||
bits
|
||
2048 (See Note 2)
|
||
400k approx.
|
||
Message Types Supported
|
||
N/A
|
||
Short and long
|
||
Notes: 1. BER applies for signal level of -164 dBW and Receiver Noise Temperature of 300 K.
|
||
2. The SARP-3 has a mode which increases the memory to 2,560 messages. This mode
|
||
can only be activated on command by the payload provider.
|
||
SARP-3 processors will include a capability to process a new type of Cospas-Sarsat distress
|
||
beacon that would enhance performance by providing a better link budget. Such beacons are not
|
||
yet available for operational use, however, technical details on their modulation characteristics
|
||
may be obtained from the Cospas-Sarsat Secretariat.
|
||
|
||
4-15
|
||
|
||
Figure 4-10: Sarsat SARP-3 Functional Diagram
|
||
2.4 kbps PDS to SARR
|
||
RF Input
|
||
Power
|
||
Supplies
|
||
Telemetry
|
||
Commands
|
||
Frame Formatter and Memory
|
||
Receiver
|
||
Control
|
||
Unit
|
||
DRU 1
|
||
DRU 2
|
||
DRU 3
|
||
Search Unit
|
||
A/D
|
||
4.2.2.1 Sarsat SARP-3 Receiver Processor
|
||
The SARP-3 instrument has similar performance to the SARP-2 instrument. The basic structure
|
||
of the format of the data it provides mimics the format provided by the SARP-2, however, there
|
||
are a few minor changes in the position of some of the bits.
|
||
The digital processing employed by the SARP-3 enable it to provide the S/No of beacon messages
|
||
that it processes. Also, on command from the satellite operator, the instrument can be commanded
|
||
to transmit House-Keeping (HK) messages in the
|
||
2.4 kbps PDS data stream. These messages are transmitted for reception by the French ground
|
||
segment and should be ignored by all other LEOLUTs. HK messages are identified by the
|
||
following:
|
||
Word 2 = 110 011 100 011 111 000 000 000; and
|
||
the BCH code provided in words 4 and 5 is consistent with the data in words 2,
|
||
3,4 and 5 that it protects.
|
||
The Sarsat SARP-3 HK message structure is provided at Figure 4.14.
|
||
|
||
|
||
|
||
|
||
|
||
4-16
|
||
|
||
4.2.2.2 Sarsat SARP-3 Output Format
|
||
Beacon messages from the Sarsat SARP-3 are transmitted in blocks of 25 words as shown in the
|
||
example of Figure 4.11.
|
||
Prime format rules are:
|
||
Zero words 'H000001'(Hex) are inserted at the end of each short message as
|
||
necessary;
|
||
Word # 00 = always frame sync '42BB1F'(Hex);
|
||
If read continuous mode is active and if the oldest playback message has just been
|
||
transmitted, a block of eight zero words will precede resumption of playback
|
||
which will start with the first word of the most recently stored message; and
|
||
If no message must be transmitted (at the beginning when no message has been
|
||
received or when the read continuous mode is inactive), blocks of eight zero words
|
||
H000001 are transmitted.
|
||
Real time messages are transmitted approximately 15 seconds after their reception by the SARP.
|
||
The bit format for both length of message formats are shown in Figures 4.12 and 4.18, where the
|
||
Most Significant Bit (MSB) of Word 0 is transmitted first. All words contains the following
|
||
information:
|
||
Word 0:
|
||
Sync word 'HD60' (Hex) followed by 6 bits described in the figure and then
|
||
the signal level. The received level, Pe, is given by:
|
||
Pe (dBm) = - 140 + LEVEL* 0.55
|
||
where LEVEL is a value between 0 and 63 defined by final six bits in Word
|
||
0.
|
||
Word 1:
|
||
The time code is quantized in steps of 's' ms and synchronised with the
|
||
beginning of the Doppler count. The last bit is a parity bit. The quantization,
|
||
which is assigned the variable value s in the equations below, is defined by:
|
||
ms
|
||
|
||
Hz
|
||
|
||
200,000
|
||
F
|
||
200,000
|
||
s
|
||
|
||
r
|
||
≈
|
||
=
|
||
=
|
||
where Fr is the exact frequency of oscillator (the nominal frequency of the
|
||
oscillator is approx 10 MHz)
|
||
The UTC time T is given by: T = To + 223ks + s(Md + 1)
|
||
Where Md = decimal value of the 23-bit on-board time code;
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
4-17
|
||
|
||
To = UTC of an arbitrarily chosen reset to zero of the counter; and
|
||
k = Number of resets to zero of the counter between time To and time T.
|
||
The value of k is computed in ground processing, for each message, with a
|
||
coarse estimate Te of T as the integer part of:
|
||
(
|
||
)
|
||
T
|
||
T
|
||
s
|
||
e
|
||
o
|
||
−
|
||
±
|
||
|
||
|
||
The coarse estimate Te can be obtained either by processing a time
|
||
calibration beacon message from stored data or from the real time when
|
||
processing local mode data. The time calibration beacon is described in
|
||
C/S T.006.
|
||
Words 2 to 4: Message format followed by 71 bits of the beacon message.
|
||
Word 5a:
|
||
Last 16 bits of beacon short message data followed by 8 zeros.
|
||
Word 5b:
|
||
24 bits of beacon long message data.
|
||
Words 6a and 7b: 23-bit Doppler word with parity. The frequency at the input of the
|
||
satellite receiver, Fin, is given by:
|
||
Fo
|
||
Fr
|
||
\*
|
||
|
||
.0
|
||
\*
|
||
Doppler
|
||
Fo
|
||
\*
|
||
|
||
|
||
Fin
|
||
|
||
|
||
|
||
|
||
|
||
|
||
+
|
||
=
|
||
where the nominal USO frequency, Fo = 107 Hz
|
||
Fr = exact frequency of the USO (if available)
|
||
Doppler =
|
||
signed integer value between –222 and +222-1 defined by
|
||
23 bits with two’s complement.
|
||
Word 6b:
|
||
Last 24 bits of beacon long message data.
|
||
Word 7a:
|
||
Zero word "H000001 (Hex)".
|
||
Note: Fr is the frequency of the SARP Ultra Stable Oscillator. LEOLUTs
|
||
should use a recent estimate of the USO frequency, as provided in a recent
|
||
SARP calibration message (SIT 415) or as calculated by the LEOLUT, for
|
||
determining the time and frequency of the beacon burst.
|
||
To is the UTC of an arbitrarily chosen time of reset to zero of the SARP
|
||
time counter. For calculating the time of a beacon burst, LEOLUTs should
|
||
|
||
4-18
|
||
|
||
use a recent To value as provided in a recent SIT 415 message or as
|
||
calculated by the LEOLUT.
|
||
Figure 4-11: Example of a Sarsat SARP-3 Output Message
|
||
Word
|
||
Word Content (Hex)
|
||
|
||
42BB1F
|
||
|
||
HD60…
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
HD60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Short
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
H000001
|
||
|
||
HD60…
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
|
||
……
|
||
Long
|
||
|
||
……
|
||
Message
|
||
|
||
……
|
||
|
||
……
|
||
|
||
H42BB1F
|
||
|
||
HD60…
|
||
|
||
……
|
||
.
|
||
.
|
||
.
|
||
|
||
4-19
|
||
|
||
Figure 4-12: Sarsat SARP-3 Short Message Bit Format
|
||
Word \#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
S/No
|
||
Type
|
||
latest
|
||
RT/PB
|
||
level
|
||
(12 bits)
|
||
(3b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(6b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 5)
|
||
|
||
Format
|
||
Beacon
|
||
data
|
||
(23
|
||
bits)
|
||
(1b)
|
||
(note 6)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
5a
|
||
Beacon data (16 bits)
|
||
8 0's
|
||
6a
|
||
Doppler word (23 bits)
|
||
Parity (1 bit) (note 5)
|
||
7a
|
||
"zero word" (24 bits) = H000001 (hex)
|
||
Figure 4-13: Sarsat SARP-3 Long Message Bit Format
|
||
Word \#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
Sync word
|
||
S/No
|
||
Type
|
||
latest
|
||
RT/PB
|
||
level
|
||
(12 bits)
|
||
(3b)
|
||
(1b)
|
||
(1b)
|
||
(1b)
|
||
(6b)
|
||
Notes:
|
||
(1)
|
||
(2)
|
||
(3)
|
||
(4)
|
||
|
||
Time code (23 bits)
|
||
Parity (1 bit) (note 5)
|
||
|
||
Format
|
||
Beacon data (23 bits)
|
||
(1b)
|
||
(note 6)
|
||
|
||
Beacon data (24 bits)
|
||
|
||
Beacon data (24 bits)
|
||
5b
|
||
Beacon data (24 bits)
|
||
6b
|
||
Beacon data (24 bits)
|
||
7b
|
||
Doppler word (23 bits)
|
||
Parity (1 bit) (note 5)
|
||
Notes
|
||
:
|
||
(1)
|
||
S/NO in 8 steps as defined in the following table:
|
||
code
|
||
S/NO
|
||
code
|
||
S/NO
|
||
|
||
32.3 (31 ≤ S/NO < 33.7)
|
||
|
||
45.2 (43.0 ≤ S/NO < 47.4)
|
||
|
||
34.8 (33.7 ≤ S/NO < 35.9)
|
||
|
||
50.1 (47.4 ≤ S/NO < 52.8)
|
||
|
||
37.5 (35.9 ≤ S/NO< 39.2)
|
||
|
||
55.5 (52.8 ≤ S/NO < 58.3)
|
||
|
||
41.1 (39.2 ≤ S/NO < 43.0)
|
||
|
||
62.1 (58.3 ≤ S/NO < 66)
|
||
(2)
|
||
"1" = Cospas-Sarsat Beacon (document C/S T.001); "0" = new type beacon.
|
||
(3)
|
||
"1" = most recent message(playback); "0" = others.
|
||
(4)
|
||
"1" = real time message; "0" = playback message.
|
||
(5)
|
||
Parity: "1" = odd number of "1s" in the 23-bit time code or the 23-bit Doppler word.
|
||
(6)
|
||
"1" = long message; "0" = short message.
|
||
|
||
4-20
|
||
|
||
Figure 4-14: Sarsat SARP-3 House-Keeping (HK) Message Bit Format
|
||
Word
|
||
\#
|
||
MSB
|
||
Word Content(24 bits)
|
||
LSB
|
||
|
||
HK data (24 bits)
|
||
|
||
HK data (24 bits)
|
||
|
||
110 011 100 011 111 000 000 000
|
||
|
||
HK data (24 bits)
|
||
|
||
HK data (13 bits)
|
||
First ll bits of BCH
|
||
|
||
Last 10 bits of BCH
|
||
HK data (14 bits)
|
||
|
||
HK data (24 bits)
|
||
|
||
HK data (24 bits)
|
||
– END OF SECTION 4 –
|
||
|
||
5-1
|
||
|
||
5.
|
||
COSPAS-SARSAT ANTENNAS
|
||
Cospas Antennas
|
||
As shown in Figure 5.1, two antennas (one receive and one transmit) have been
|
||
provided on the spacecraft in support of the Cospas payload.
|
||
5.1.1
|
||
Cospas Receive Antennas
|
||
Cospas receive antennas (SPA for 406 MHz) have the following characteristics:
|
||
Polarisation:
|
||
LHCP for 406 MHz
|
||
Gain:
|
||
As shown in Figures 5.2
|
||
Maximum and minimum contours of antenna gain referred to the receiver
|
||
input when illuminated with a rotating linear source
|
||
Axial ratio:
|
||
As derived by the maximum and minimum contours on gain Figures
|
||
Frequency:
|
||
406.05 MHz ±50 kHz
|
||
5.1.2
|
||
Cospas Transmit Antenna
|
||
Cospas transmit antenna (SLA) has the following characteristics:
|
||
Polarisation:
|
||
LHCP
|
||
Gain (referred to the transmitter output port):
|
||
As shown in Figures 5.3
|
||
Minimum antenna gain on LHCP with an axial ratio ≤6 dB over 90% of
|
||
region defined by 0º ≤ azimuth ≤ 360º and by 0º ≤ nadir ≤ 60º
|
||
Axial ratio:
|
||
As stated in gain Figure
|
||
Frequency:
|
||
1544.5 MHz ±500 kHz
|
||
|
||
|
||
|
||
5-2
|
||
|
||
Figure 5-1:
|
||
Cospas Antenna System Functional Diagram
|
||
Figure 5-2:
|
||
Cospas (SARP-2) 406 MHz Receive Antenna (SPA) Gain Pattern
|
||
|
||
|
||
|
||
|
||
|
||
5-3
|
||
|
||
Figure 5-3:
|
||
Cospas (SARP-2) 1544.5 MHz Transmit Antenna (SLA) Gain Pattern
|
||
Sarsat-TIROS Antennas
|
||
As shown in Figure 5.5, three antennas (two receive and one transmit) have been installed on
|
||
the spacecraft with necessary diplexers and filters in support of the Sarsat payload.
|
||
5.2.1
|
||
Sarsat-TIROS Receive Antennas
|
||
The SARR Receive Antenna (SRA) is a coaxial quadrifilar antenna.
|
||
The SARP receive antenna signal comes from the quadrifilar UHF Data collection system
|
||
Antenna (UDA).
|
||
Sarsat receive antennas have the following characteristics:
|
||
Polarisation:
|
||
RHCP
|
||
Gain:
|
||
Minimum gain (RHCP) over 90% As shown in Figures 5.5 to 5.6
|
||
Axial ratio:
|
||
As derived by the maximum and minimum contours on gain Figures
|
||
Frequency:
|
||
SARR:
|
||
406.05 MHz ±50 kHz
|
||
SARP:
|
||
406.05 MHz ±50 kHz
|
||
5.2.2
|
||
Sarsat-TIROS Transmit Antenna
|
||
The SARR L-band transmit Antenna (SLA) is a quadrifilar antenna that has been optimised to
|
||
produce a hemispherical pattern.
|
||
|
||
|
||
|
||
|
||
|
||
5-4
|
||
|
||
Sarsat transmit antenna has the following characteristics:
|
||
Polarisation:
|
||
LHCP
|
||
Gain (referred to the transmitter output port):
|
||
As shown in Figures 5.7
|
||
Axial ratio:
|
||
As stated in gain Figure
|
||
Frequency:
|
||
1544.5 MHz ±500 kHz
|
||
Figure 5-4:
|
||
Sarsat-TIROS Antenna System Functional Diagram
|
||
SLA
|
||
1544.5 MHz
|
||
Transmitter
|
||
SRA
|
||
406.05 MHz
|
||
SARR Input
|
||
Filter
|
||
UDA
|
||
RF Switch
|
||
SARP Input
|
||
To Non-Sarsat
|
||
payloads
|
||
Filter
|
||
Filter
|
||
SLA
|
||
1544.5 MHz
|
||
Transmitter
|
||
SLA
|
||
1544.5 MHz
|
||
Transmitter
|
||
SRA
|
||
406.05 MHz
|
||
SARR Input
|
||
Filter
|
||
SRA
|
||
406.05 MHz
|
||
SARR Input
|
||
Filter
|
||
UDA
|
||
RF Switch
|
||
SARP Input
|
||
To Non-Sarsat
|
||
payloads
|
||
Filter
|
||
Filter
|
||
|
||
5-5
|
||
|
||
Figure 5-5:
|
||
Sarsat-TIROS 406.05 MHz Receive Antenna (SRA) Gain Pattern
|
||
(at receiver input)
|
||
Antenna gain referenced to the receiver input, when illuminated with a rotating linear source.
|
||
|
||
|
||
|
||
5-6
|
||
|
||
Figure 5-6:
|
||
Sarsat-TIROS SARP Receive Antenna (UDA) Gain Pattern (at receiver
|
||
input)
|
||
Antenna gain referenced to the receiver input, when illuminated with a rotating linear source.
|
||
* Region defined by 0° ≤ azimuth ≤ 360° and 0° ≤ nadir ≤ 60°
|
||
|
||
|
||
|
||
5-7
|
||
|
||
Figure 5-7:
|
||
Sarsat-TIROS 1544.5 MHz Transmit Antenna (SLA) Gain Pattern
|
||
* Region defined by 0° ≤ azimuth ≤ 360° and 0° ≤ nadir ≤ 60°
|
||
Sarsat-METOP Antennas
|
||
As shown in Figure 5.8, two antennas (one receive and one transmit) have been installed on the
|
||
spacecraft with necessary diplexers and filters in support of the Sarsat-METOP payload.
|
||
5.3.1
|
||
Sarsat-METOP Receive Antennas
|
||
The Combined Receive Antenna (CRA) combines the receive antenna for SARP and SARR into
|
||
one helical antenna. It is operating at 406 MHz and is connected to both SARR and SARP
|
||
instruments.
|
||
The CRA Antenna is deployable.
|
||
Sarsat-METOP receive antenna (CRA) has the following characteristics:
|
||
Polarisation:
|
||
RHCP
|
||
Gain:
|
||
As shown in Figures 5.9
|
||
Axial ratio:
|
||
As derived by the maximum and minimum contours on gain Figures
|
||
Frequency:
|
||
SARP/SARR: 406.05 MHz ±50 kHz
|
||
|
||
|
||
|
||
|
||
|
||
5-8
|
||
|
||
5.3.2
|
||
Sarsat-METOP Transmit Antenna
|
||
The SARR L-band transmit Antenna (SLA) is a conventional quadrifilar helix that has been
|
||
optimised to produce a hemispherical pattern.
|
||
Sarsat-METOP transmit antenna has the following characteristics:
|
||
Polarisation:
|
||
LHCP
|
||
Gain (referred to the transmitter output port):
|
||
As shown in Figures 5.10
|
||
Axial ratio:
|
||
As stated in gain Figure
|
||
Frequency:
|
||
1544.5 MHz ±500 kHz
|
||
Figure 5-8:
|
||
Sarsat-METOP Antenna System Functional Diagram
|
||
1544.5 MHz
|
||
Transmitter
|
||
SLA
|
||
Filter
|
||
CRA
|
||
Diplexer
|
||
406 MHz SARR Input
|
||
To Non-Sarsat payloads
|
||
Filter
|
||
LNA
|
||
406 MHz SARP Input
|
||
1544.5 MHz
|
||
Transmitter
|
||
SLA
|
||
Filter
|
||
CRA
|
||
Diplexer
|
||
406 MHz SARR Input
|
||
To Non-Sarsat payloads
|
||
Filter
|
||
LNA
|
||
406 MHz SARP Input
|
||
|
||
5-9
|
||
|
||
Figure 5-9: Sarsat-METOP 406 MHz SARR and SARP Receive Antenna (CRA)
|
||
Gain Pattern (at receiver input)
|
||
Figure 5-10: Sarsat-METOP 1544.5 MHz Transmit Antenna (SLA) Gain Pattern
|
||
Sarsat-NPOESS Antennas
|
||
As shown in Figure 5.11, two antennas (one receive and one transmit) have been installed on
|
||
the spacecraft with necessary accommodation hardware in support of the Sarsat-NPOESS
|
||
payload.
|
||
|
||
|
||
Angle Off Nadir (Deg)
|
||
Gain (dBiC)
|
||
Predicted Average Gain
|
||
(min of all phi cuts)
|
||
Predicted Average Gain
|
||
(max of all phi cuts)
|
||
Predicted Average Gain
|
||
(average of all phi cuts)
|
||
|
||
|
||
|
||
|
||
|
||
5-10
|
||
|
||
5.4.5
|
||
Sarsat-NPOESS Receive Antenna
|
||
(description TBD by USA)
|
||
Sarsat-NPOESS receive antenna has the following characteristics:
|
||
Polarisation:
|
||
RHCP
|
||
Gain:
|
||
As shown in Figure 5.12 for 95% of the azimuth angles and any nadir
|
||
angle
|
||
Center Frequency:
|
||
403 MHz ± 30 MHz (TBC by USA)
|
||
5.4.6
|
||
Sarsat-NPOESS Transmit Antenna
|
||
(description TBD by USA)
|
||
Sarsat-NPOESS transmit antenna has the following characteristics:
|
||
Polarisation:
|
||
LHCP
|
||
Gain:
|
||
As shown in Figure 5.13 for 95% of the azimuth angles and any nadir
|
||
angle
|
||
Axial ratio:
|
||
For 99% of the azimuth angle and any nadir angle between 0 and 61.97
|
||
deg.
|
||
Frequency:
|
||
1544.5 MHz ±500 kHz
|
||
Figure 5-11: Sarsat-NPOESS Antenna System Functional Diagram
|
||
|
||
|
||
|
||
5-11
|
||
|
||
Figure 5-12: Sarsat-NPOESS Receive Antenna Gain Pattern
|
||
(TBC by USA)
|
||
SARSAT NPOESS Receive Antenna Gain
|
||
|
||
|
||
5 10 15 20 25 30 35 40 45 50 55 60 65
|
||
Nadir Angle (deg)
|
||
Gain (dBiL)
|
||
Maximum Gain
|
||
(dBiL)
|
||
Minimum Gain
|
||
(dBiL)
|
||
Figure 5-13: Sarsat-NPOESS Transmit Antenna Gain Pattern
|
||
(TBC by USA)
|
||
SARSAT NPOESS TRANSMIT ANTENNA GAIN
|
||
|
||
|
||
10 15 20 25 30 35 40 45 50 55 60 65
|
||
Nadir Angle (deg)
|
||
Gain dBiL
|
||
Minimum Gain
|
||
(dBiL)
|
||
– END OF SECTION 5 –
|
||
|
||
ANNEXES TO
|
||
DESCRIPTION OF THE
|
||
PAYLOADS USED IN THE
|
||
COSPAS-SARSAT LEOSAR SYSTEM
|
||
|
||
A-1
|
||
|
||
ANNEX A:
|
||
LIST OF ABBREVIATIONS AND ACRONYMS
|
||
AGC
|
||
Automatic Gain Control
|
||
BTA
|
||
Beacon Transmit Antenna (NOAA satellite)
|
||
COSPAS
|
||
COsmicheskaya Sistema Poiska Avarinykh Sudov (Russian equivalent to
|
||
SARSAT)
|
||
C/S
|
||
Cospas-Sarsat
|
||
dB
|
||
decibel
|
||
dBLi
|
||
gain in decibels relative to a linear isotropic antenna
|
||
dBm
|
||
power in decibels relative to 1 milliwatt
|
||
dBW
|
||
power in decibels relative to 1 Watt
|
||
DRU
|
||
Data Recovery Unit
|
||
EIRP
|
||
Equivalent Isotropically Radiated Power
|
||
FF
|
||
Frame Formatter
|
||
hex
|
||
hexadecimal
|
||
IF
|
||
Intermediate Frequency
|
||
K
|
||
Kelvin (degrees)
|
||
kbps
|
||
kilo bits per second
|
||
LHCP
|
||
Left Hand Circular Polarisation
|
||
LSB
|
||
Least Significant Bit
|
||
LUT
|
||
Local User Terminal
|
||
METOP
|
||
European Meteorological Operational satellite programme
|
||
MIRP
|
||
Manipulated Information Rate Processor (on NOAA satellite)
|
||
MSB
|
||
Most Significant Bit
|
||
N/A
|
||
not applicable
|
||
NOAA
|
||
National Oceanic and Atmospheric Administration (USA)
|
||
NPOESS
|
||
National Polar-orbiting Operational Environmental Satellite System
|
||
NRZ-L
|
||
Non Return to Zero biphase-L data encoding
|
||
|
||
A-2
|
||
|
||
LIST OF ABBREVIATIONS AND ACRONYMS
|
||
(Continued)
|
||
PB
|
||
Playback
|
||
PDS
|
||
Processed Data Stream
|
||
PM
|
||
Phase Modulation
|
||
PTC
|
||
Power, Telemetry and Command
|
||
rad
|
||
radian(s)
|
||
RF
|
||
Radio Frequency
|
||
RHCP
|
||
Right Hand Circular Polarisation
|
||
RMS
|
||
Root Mean Square
|
||
RT
|
||
Real Time
|
||
SAR
|
||
Search And Rescue
|
||
SARP
|
||
Search And Rescue Processor
|
||
SARP-1
|
||
SARP with memory
|
||
SARP-2
|
||
Second generation SARP with memory
|
||
SARP-3
|
||
Third generation SARP with memory
|
||
SARR
|
||
Search And Rescue Repeater
|
||
SARR-1
|
||
First generation of SARR
|
||
SARR-2
|
||
Second generation of SARR (PDS channel only)
|
||
SARSAT
|
||
Search And Rescue Satellite Aided Tracking
|
||
SBA
|
||
NOAA S-band transmit antenna
|
||
SLA
|
||
SARR L-band transmit antenna SPA SARP receive antenna
|
||
SRA
|
||
SARR receive antenna
|
||
TC
|
||
Telemetry command from spacecraft interface to SAR payload
|
||
TIP
|
||
TIROS Information Processor (NOAA satellite) TIROS Television Infrared
|
||
Observation Satellites
|
||
TM
|
||
Telemetry information from SAR payload to spacecraft interface
|
||
UDA
|
||
UHF data collection system antenna (NOAA satellite) UTC Universal Time
|
||
Co-ordinated
|
||
VCO
|
||
Voltage Controlled Oscillator
|
||
- END OF ANNEX A -
|
||
|
||
B-1
|
||
|
||
ANNEX B:
|
||
COSPAS-SARSAT LEOSAR FREQUENCIES
|
||
B.1
|
||
Introduction
|
||
The 1992 ITU World Administrative Radio Conference (WARC 92) addressed the worldwide use
|
||
and allocation of the radio spectrum, including mobile satellite services.
|
||
Cospas-Sarsat, an international satellite system for search and rescue, provides a distress alerting
|
||
and locating service using distress beacons operating on 406 MHz, a constellation of satellites, a
|
||
number of ground receiving stations (called Local User Terminals, LUTs) and a network of
|
||
Mission Control Centres which distribute the alert and location data to search and rescue
|
||
authorities.
|
||
The 406 MHz Cospas-Sarsat System has been adopted by the International Maritime Organization
|
||
as part of the Global Maritime Distress and Safety System (GMDSS).
|
||
B.2
|
||
Frequency Matters
|
||
B.2.1
|
||
Frequency Requirements
|
||
The Cospas-Sarsat Council considers it essential that the existing frequency allocations for
|
||
Cospas-Sarsat remain in effect, because Cospas-Sarsat satellite payloads are already being built
|
||
for use into the foreseeable future, with more than 30 ground receiving stations installed world-
|
||
wide, any changes to operating frequencies would be very difficult to implement.
|
||
The frequencies used by the Cospas-Sarsat LEOSAR System are identified in the radio regulations
|
||
(Table B.1 refers), and the Cospas-Sarsat instruments using these frequency bands have been
|
||
registered with the ITU.
|
||
Prior to each open field test site transmission, the appropriate national authorities responsible for
|
||
Cospas-Sarsat and radio emissions shall be notified.
|
||
In order to keep the potential disturbance to the Cospas-Sarsat System to a minimum, these antenna
|
||
tests shall be conducted using a beacon operating at its nominal repetition rate and coded with the
|
||
test protocol of the appropriate type and format. Transmission of any continuous wave (CW) signal
|
||
from a signal generator in the 406.0 - 406.1 MHz band is strictly forbidden.
|
||
|
||
B-2
|
||
|
||
B.2.2
|
||
Interference
|
||
The international community has recognised the negative impact that interference could have on
|
||
Cospas-Sarsat operations. To mitigate the risk, the ITU has approved a recommendation (ITU-R
|
||
M.1478) which identifies the maximum interference levels which could be tolerated by Cospas
|
||
and Sarsat SARP instruments.
|
||
Table B-1:
|
||
Cospas Sarsat LEOSAR Frequencies
|
||
Frequencies
|
||
Earth-to-space
|
||
Space-to-earth
|
||
Centre
|
||
frequency
|
||
Bandwidth
|
||
ITU Radio
|
||
Regulation
|
||
Footnote
|
||
Centre Frequency
|
||
Bandwidth
|
||
ITU Radio
|
||
Regulation
|
||
Footnote
|
||
406.05 MHz
|
||
100 kHz
|
||
S5.266 & S5.267
|
||
1544.5 MHz
|
||
1000 kHz
|
||
S5.354 & S5.356
|
||
- END OF ANNEX B –
|
||
- END OF DOCUMENT –
|
||
|
||
Cospas-Sarsat Secretariat
|
||
1250 René-Lévesque Blvd. West, Suite 4215, Montreal (Quebec) H3B 4W8 Canada
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Telephone: +1 514 500 7777
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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 |