); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY On Thu, 4 Oct 2007, Brooke Clarke wrote: > > It's interesting to tracing the path from the doppler data which was used to > determine the slant range between he satellite and the receiver antenna. > Some cleaver thinking then leads to the idea that you can determine were you > are if you know the satellite orbital parameters.
Dear Brooke and friends, You have described the actual method of position determination for the COSPAS/SARSAT search and rescue system. The original ELTs (emergency location beacon transmitters) on 121.5, 243, and around 403MHz were in use on ships, lifeboats, and airplanes long before GPS. So they basically only could transmit a modulated carrier. How to find the location of a distress signal before you can send out aircraft to fly over the area? You put up a number of NON-stationary satellites that all receive these frequencies then convert their doppler shift to sub-carriers on a microwave transmitter that is downlinked to coast guard stations all over the world. These have a tracking system and also a dedicated special purpose computer that calculates the location of the ELT from the orbital information of the satellite that received the signal and the doppler shift of the VHF or UHF signal from the ELT. Then planes and resue ships are dispatched. This program was a cooperative effort of the US, Canada, France and the Soviet Union. Each contributed a portion of the design. I designed the ground station receiver and tracking system and was sent by NASA to Moscow in 1982 for the final test in a lab with all the hardware from each country. Regards, Jeffrey Pawlan _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
