NavList:

Don Seltzer, you wrote:
"Suppose there is an observer directly below the Inmarsat satellite, at about 64°E, 0°. The satellite is 22,236 miles away at this moment, but moving 'north' at 100 mph. An hour later, how much has the distance from the observer to the satellite changed? I calculate less than 1/4 mile in that hour."

I haven't checked your calculation, but off the top of my head, it sounds quite reasonable. Doppler shift only comes into play as the ground station (aircraft in this case) moves into higher latitude. Again, this is towards the end of the projected flight, which is what we're all interested in. I apologize if I misunderstood your previous comment. If you were just saying that there is a geometric factor to deal with, then yes, of course that is true. But it's symmetrical, north and south of the equator yielding the same pattern. The only way that I can think of to "de-symmetrize" the north and south arcs via a Doppler shift, as reported, is through the satellite's own north-south motion. And even though the orbital inclination is quite small, at that range it's a substantial north-south speed at least relative to the speed of a jet at cruising altitude. IF the satellite were in a true geostationary orbit, it would be above the equator with no north-south oscillation and, as far as I can see it, no way to distinguish between those two arcs.

Of course, I could be way off. I'm just describing it as I see it right now.

-FER

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