SARP-3

The Search And Rescue Processor (SARP-3) instrument is one of the complement of American instruments provided by the National Oceanic and Atmospheric Administration (NOAA) to fly on MetOp-A and B.

SARP-3 receives and processes emergency signals from the 406 MHz beacons on aircraft and ships in distress. It determines the name, frequency and time of the signal. These pre-processed data are then fed in real-time to the Search And Rescue Repeater (SARR) instrument for immediate transmission to SARSAT (Search and Rescue Satellite) distress terminals on the ground.

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.

The Search and Rescue instrument (SARP-3) is part of the international COSPAS-SARSAT system, which has been integrated into the overall Global Maritime Distress Safety System (GMDSS).

SARP-3 is designed to detect and locate Emergency Locator Transmitters (ELTs), Emergency Position-Indicating Radio Beacons (EPIRBs), and Personal Locator Beacons (PLBs) operating at 406.05 MHz. The Search and Rescue Repeater (SARR) which complements the Search and Rescue payload on MetOp is presented separately. Both instruments are already well established.

The National Oceanic and Atmospheric Administration (NOAA) spacecraft carries two instruments to detect these emergency beacons; the Search and Rescue Repeater (SARR) provided by Canada and the Search and Rescue Processor (SARP-2) provided by France. Similar instruments are carried by the Russian COSPAS polar-orbiting satellites.

The SARP-3 detects the signal from 406.05 MHz beacons and stores the information for subsequent down-link to a Local User Terminal (LUT). Thus, global detection of 406.05 MHz emergency beacons is provided which is a requirement of the GMDSS. After receipt of information from a satellite's SARP, a LUT locates the beacons by Doppler processing. The principle of the Doppler processing is that a transmitter signal will have different frequencies depending on its location in relation to the receiver. The determined beacon frequency by the SARP-3 differs depending on the relative velocity between beacon transmitter and the SARP-3 receiver. The 406.05 MHz beacons are located with an accuracy of approximately 4 km (2.5 mi). The LUT forwards the located distress message to a nearby Mission Control Center (MCC), which forwards the information to a Rescue Co-ordination Center.

SARP-3 is provided by Centre National d'Etudes Spatiales (CNES) Toulouse, France and developed by Thales Elancourt, France, and Alcatel Space Toulouse, France.