kcarroll (09/17/82)
According to today's morning edition of the Toronto Star, a satellite-based search-and-rescue system was used (yesterday?) to locate a small aircraft that had crashed in the mountains of British Columbia. The satellite that detected the signal from the aircraft's Emergency Transmitter Locator (ETL) was a Soviet one, Cospas 1, launched last July 30. The signal from the satellite was received at a Canadian Forces search-and-rescue station at Shirley Bay, outside Ottawa, the day after the crash. Cospas 1 is in a low (960 km) orbit, covering Canada once every 12 hours, if I decode the news-reporter's phraseology correctly. Conincidentally, I attended a lecture by an employee of SPAR aerospace (of Canadarm fame) last week--he described this satellite system, which I beleive his company had a hand in, and mentioned that while no rescues had yet been attributed to the satellites, they expected them to prove themselves in the near future! The system, I beleive, is comprised of three satellites, one Canadian, one French and one Soviet, in high-inclination orbits. The search-and-rescue equipment flies as a secondary payload on these satellites. It works by receiving the low-power (1 watt) ETL signals from downed aircraft, and either relaying them to ground stations, or finding the frequency shift in the signal due to the relative velocity of the satellite with respect to the ETL, which is then transmitted to the ground stations. In any case, the Doppler-shift of the ETL is found, and is decoded on the ground to determine the position of the downed aircraft. In this case, the satellite data located the aircraft to "within a few kilometres" of its actual position. Not bad! (Oh yes. Three people were rescued: G. Van Amelsvoort, J.Zaigleheim, and G. Heemskerk, all from the Toronto area. An air-based search for th aircraft the previous night had failed. The satellite's success was attributed by the Armed Forces to its being high enough to "avoid natural interference".) -Kieran A. Carroll