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The keystone to the Cospas-Sarsat System are the polar orbiting satellites from which the system takes its name. These satellites provide the ability to detect and locate 406 MHz alerts worldwide and 121.5 MHz alerts for about sixty percent of the world. In addition to the polar orbiting satellites, the system is currently evaluating the use of geostationary orbiting satellites. These satellites have several advantages and several disadvantages. For more about them see Cospas-Sarsat Enhancements. SARSAT is an instrument package flown aboard the NOAA Series of environmental satellites operated by NOAA's National Environmental Satellite, Data and Information Service (NESDIS). These satellites orbit at an altitude of 528 miles and complete an orbit every 100 minutes. Their orbits are inclined 99 degrees from the equator. Each satellite carries a Search and Rescue Repeater (SARR) which receives and retransmits 121.5 MHz and 243 MHz signals anytime the satellite is in view of a ground station. Also carried is a Search and Rescue Processor (SARP) which receives 406 MHz transmissions, provides measurements of the frequency and time, then retransmits this data in real-time and stores it aboard for later transmission. If the satellite is in view of a ground station when a 406 MHz signal is received the data is received in real-time. The satellite also stores each signal it receives and continuously downloads this data. If the satellite was not in view of a ground station when it received a beacon signal, the next ground station that sees that satellite will receive the data. This provides global coverage for 406 MHz distress signals. The SARR is provided by the Canadian Department of National Defence and the SARP is provided by the French Center National D'Etudes Spatiales (CNES). The COSPAS instrument is carried aboard the NADEZHDA navigation satellite orbiting the Earth every 105 minutes at an altitude of 620 miles and an orbital inclination of 83 degrees. The COSPAS instrument was built by the former Soviet Union and continues to be operated by the Russian Federation. The only major difference between COSPAS and SARSAT is that the Russian satellites do not receive 243 MHz distress signals.
SATELLITE STATUSUnited States Satellites:
For further information on the Polar Orbiting Environmental Satellites utilized by SARSAT, check out the NASA Goddard Space Flight Center (Code 480) Homepage.
For further information about the Geostationary Orbiting Environmental Satellites, check out the NASA Goddard Space Flight Center (Code 415) Homepage. Russian Satellites:
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