Doppler shift in appendix G of ATSB report for the MH370 incident
1. Why should the Aircraft Latitude affect the Doppler frequency shift?


It seems to me that table 6 is a check to test whether the equation on page 55 can reliably be used to predict the possible locations of an aircraft from a measured BFO. It does this by using the equation to predict what the BFO should be for a given set of inputs and comparing that with the measured BFO. To see how reliable this is they vary one of the parameters, latitude in this example, to show that the predicted BFO is considerably different for different latitudes and that the best match of predicted BFO to the measured BFO is for the known location of the aircraft. Therefore you know that the BFO is useful - it can be used to rule out some locations.

If you hold constant all the other factors and vary latitude why should that affect BFO?

I guess it's because for the same aircraft heading (with respect to true north), different latitudes but same headings mean different angles of flight with respect to the satellite. That means that there are different magnitudes of component of velocity that is parallel to the line from satellite to aircraft - those different magnitudes represent different speeds in a line directly away-from or directly towards the satellite. This affects doppler.



Note: The above doesn't explain why ΔFdown varies with aircraft latitude.



Other independent analyses of this data


Dr Richard E Cole, University College London
Dr Duncan Steele (who asks the same question)


I'm pretty sure Duncan Steele is smarter than me, so you may be on to something.




  2. However, I can only derive this exact frequency using the satellite velocity for UTC time 16:55:00?


That's more of a statement than a question. I guess your question is:


  why do my calculations give a different answer?


I see two possibilities


you made a mistake.
the ATSB made a mistake†.


In order for readers to help you with the first or confirm the second, you'd really have to share your calculations with us.



† And presumably Inmarsat, the NTSB, the AAIB and others.