No, BFO depends on the satellite speed and the airplane speed. The BFO sign does not reverse as the satellite moves through its apogee. If the airplane speed is constant in magnitude and direction, the rate-of-change of BFO changes gradually with the changing satellite speed.
- this is all very confusing for a simple pilot! As the satellite reverses from its northbound travel to southbound travel I cannot see why the 'error' (the BFO?) caused by the rate of change of displacement from geo-stat does not reverse since the rate has reversed? Looked at another way, why is the BFO not zero as the satellite reaches 'apogee' and the satellite 'speed' wrt geo-stat becomes zero?
Secondly, if I understand correctly (!!), there is a Doppler shift recorded by the ground station for each burst. Presumably this can be translated into an apparent radial 'ground speed' which can then be corrected by the BFO to produce a reasonbly accurate
minimum 'ground speed'. Are these values available?