[time-nuts] Airraft Ping Timing

Hal Murray hmurray at megapathdsl.net
Tue Mar 25 02:42:42 EDT 2014

n1hac at dartmouth.edu said:
> I am surprised it took them this long.  A number of satellite telemetry
> systems can use doppler as a matter of course for locating transmitters,
> such as Iridium and Argos. 

It's more complicated than just computing the Doppler.  You also have to 
figure out what the base frequency is and maybe how it changes over time.  If 
you assume the transmit frequency is stable and that the plane is flying in a 
straight line and you have several samples on a broad enough angle/Doppler 
spread, you can probably work it all out.

For Iridium, the target is fixed (or moving slowly relative to the satellite) and the satellite is moving fast so it gets a lot of angle/Doppler change to work with.

These are my opinions.  I hate spam.

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