ACR Electronics PLB-350B, 2883, 2882 manual Appendix B - The Cospas-Sarsat System, General overview

APPENDIX B - THE COSPAS-SARSAT SYSTEM

1. General overview

Beacons transmit to the satellite portion of the Cospas-Sarsat system. Cospas- Sarast satellites are an international system that utilizes Russian Federation and United States’ low altitude, near-polar orbiting satellites (LEOSAR). These satellites assist in detecting and locating activated 406 MHz satellite beacons.

Cospas-Sarsat satellites receive distress signals from beacons transmitting on the frequency of 406 MHz. The Cospas-Sarsat 406 MHz beacon signal consists of a transmission of non-modulated carriers followed by a digital message format that provides identification data. The 406 MHz system uses satellite-borne equipment to asure and store the Doppler-shifted frequency along with the beacon’s digital data message and time of measurement. This information is transmitted in real time to

an earth station called the Local User Terminal (LUT), which may be within the view of the satellite, as well as being stored for later transmission to other LUTs.

The LUT processes the Doppler-shifted signal from the LEOSAR and determines the location of the beacon, then the LUT relays the position of the distress to a Mission Control Center (MCC) where the distress alert and location information is immediately forwarded to an appropriate Rescue Coordination Center (RCC). The RCC dispatches Search and Rescue (SAR) forces.

The addition of the GEOSAR satellite system greatly improves the reaction time for a SAR event. This satellite system has no Doppler capabilities at 406 MHz, but will relay the distress alert to any of the LUT stations. When there is GPS data included in the distress message, SAR authorities instantly know your location to within 110 yards (100 m). This speeds up the reaction time by not having to wait for one of the LEOSAR satellite to pass overhead. Because most of the search and rescue forces presently are not equipped to home in on the 406 MHz Satellite beacons signal, homing must be accomplished at 121.5 MHz.

Once the 406 MHz signal is relayed through the LEOSAR and/or GEOSAR network, SAR forces determine who is closest, and then proceed to the beacon using the 121.5 MHz homing frequency.

2. Global Positioning System (GPS)

The GPS system is a satellite group that enables a GPS receiver to determine its exact position to within 30 m (100 ft.) anywhere on earth. With a minimum of 24 GPS satellites orbiting the earth at an altitude of approximately 11,000 miles they provide users with accurate information

on position, velocity, and time anywhere in the world and in all weather conditions. Beacons that have GPS engines add this data to its distress transmission, allowing search and rescue forces to narrow the search to a very small area, thus minimizing the resources required, and dramatically increasing the effectiveness of the overall operation.

Y1-03-0241A 18