[time-nuts] MH370 Doppler

Bill Hawkins bill at iaxs.net
Tue Aug 19 18:25:30 EDT 2014


As I understand it, Doppler will give you the magnitude of the velocity
vector for an aircraft with respect to the satellite, but it won't give
you the actual direction of the aircraft.

Why does the stability of the oscillators matter if you can't determine
the direction? Is there another satellite involved? Can you learn
something if you assume a velocity for the aircraft? In which case the
error in the assumed velocity would swamp the oscillator error, no?

Bill Hawkins

-----Original Message-----
From: Joe Leikhim
Sent: Monday, August 18, 2014 11:53 AM

Is anyone paying attention to all the chatter about the lost aircraft
MH370, Inmarsat's supposed flight tracks based on 6 or 7 pings (1 per
hour), the Doppler shift (BFO) and transaction timing (BTO) etc??

Basically from my perspective they are putting too much stock into the
Doppler which relies in part upon the stability of the satellite
terminal in the 777 aircraft. My question is how stable an oscillator
(reported OCXO - not confirmed)  would be under the extremes of either
or both a cabin fire or decompression event. There is a website (Duncan
Steel Blog) where some math brains are trying to sort out the raw data
provided by Inmarsat. They have made assumptions about the stability of
the local oscillator in the satellite, but I think the aircraft
satellite terminal's master oscillator is a variable they have pushed
aside.





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