(jdff) wrote in message ...
Actually I think the explanation is probably quite mundane for the
whole effect. Either the position of the Earth antenna is not exactly
where the GPS calculations put it (working in the industry, I know how
few people ever bother about the proper conversion between WGS-84
ellipsoidal co-ordinates and ECEF). Or the spacecraft has a position
co-ordinate tangential to the Earth-spacecraft line not exactly where
they think. Remember, only the RANGE is known to within metres.

Either way, that puts the observation vector off at an angle, which
introduces a small diurnal variation and probably a small systematic
error.

[s.a.r. mod. note: quoted text trimmed -- please do this yourself -- mjh]

I was not aware of that particular twist in the case.

Thanks for the link and explanation.

André Michaud