[time-nuts] Sputnik

Jeffrey Pawlan jpawlan at pawlan.com
Thu Oct 4 14:28:24 EDT 2007

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


Jeffrey Pawlan

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