Originally Posted by Ian W
They only started flying toward the Indian Ocean satellite after breaking radio contact and turning back.
As Robin Clark pointed out in his post on this subject, the aircraft on initial climb out had the satellite at - 73.17° (to the left), which meant that any Doppler shift with reference to the Inmarsat 3-F1 satellite would be increasing.
However, that is not the end of the story, as it is the aircraft that senses the Doppler shift between it and the satellite and shifts its Tx frequency to compensate. If flying toward the satellite it would shift its Tx frequency downward so that any transmission from the aircraft would arrive at the satellite at the assigned and expected Rx frequency. Likewise when flying away from the Satellite, the Doppler shift would be deceasing and the aircraft would adjust its Tx frequency in the opposite direction, i.e. upwards.
The satellite has nothing to do with the Doppler correction; that is assigned to each individual aircraft, otherwise the satellite would have a very large job on its hands when communicating with many aircraft. What the Satellite does do, is transmit a constant carrier on the P Channel which the aircraft uses to sense the received frequency offset from the assigned channel and then adjusts its Tx channel(s) in the opposite direct to compensate.
Any Doppler shift between the the Ground Station (GES) and the satellite is corrected at the earth side, which allows the separate isolation of Doppler between the Sat and the aircraft (AES).
Now start thinking about where this "burst frequency offset" info is coming from.