SARSAT

Helping save lives

The SARSAT instruments on Metop help search and rescue authorities save thousands of lives around the world.

Last Updated

06 May 2022

Published on

27 May 2020

What is Sarsat?

Sarsat-13 on Metop-B comprises of SAR signal Repeaters (SARR) and SAR signal Processors (SARP-3). Note: Metop-C does not have the Search and Rescue capability.

The Sarsat instruments on the Metop satellites, flying in low Earth orbit (LEO) and known as LEOSAR, receive messages from emergency beacons, coordinated by the COSPAS-SARSAT programme. They are downlinked to the distress terminals — known as Local User Terminals (LUT) — distributed around the globe. The message are then processed and distress alerts generated. The Mission Control Centres (MCC) receive those alerts and relay them to the appropriate Rescue Control Centre (RCC), which begins the actual search and rescue operation.

Under COSPAS-SARSAT, EUMETSAT also provides search and rescue transponders on the Meteosat Second Generation geostationary satellites.

The SARR instrument receives 406MHz beacon transmission bursts and retransmits them immediately on the dedicated 1544.5MHz downlink to the LUTs. Because there isn't a memory within SARR this service only works in local mode, i.e. the beacon and LUT must be in simultaneous view of the satellite. All processing is performed by the LUT. Each transmission is detected and the Doppler (change in wavelength caused by the motion of the satellite, with respect to the beacon) information calculated and a beacon position is then determined.

SARP receives and processes emergency signals from the 406MHz beacons. It determines the identification, frequency and time of the signal. These pre-processed data are then fed, in real time, to the SARR instrument for immediate transmission, plus simultaneously stored in the memory for additional later transfer to the LUTs. This process can locate beacons within an accuracy of 5km. A low-power 121.5MHz homing signal included in most 406 MHz beacons helps rescuers determine the final location.

This means that with a 406 MHz beacon, a distress message can be sent to the appropriate authorities, from anywhere on Earth, 24 hours a day, 365 days a year.

SARR is provided by NOAA and developed by EMS Technologies of Quebec, Canada, under contract to the Canadian Department of National Defense (DND).

SARP-3 is provided by CNES and developed by Thalès Systèmes Aéroportés (TSA).

Parameter	Details
Coverage	Global, twice daily
Mass	51.5 kg
Power	86 W
Data rate	2.4 kbps

Primary mission objective:

To relay distress signals from users in difficulty to search and rescue centres, and locate the source

Metop SARSAT instrument status and calibration

Information needed to optimise use of data from Metop SARSAT for operational and scientific applications.

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