[time-nuts] MH370 Doppler

Chris Albertson albertson.chris at gmail.com
Tue Aug 19 18:47:31 EDT 2014


You CAN determine the ground track if you assume the altitude above
sea level is constant and the aircraft's speed is also constant.  But
you are correct that Doppler alone would not be enough.

The question I have to people here is:  How does error in the dopler
translate to error in the ground track.  In other words what is the
function that maps oscillator stability to distance on the ground.

On Tue, Aug 19, 2014 at 3:25 PM, Bill Hawkins <bill at iaxs.net> wrote:
> 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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-- 

Chris Albertson
Redondo Beach, California



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