Note on apparent systematic and periodic errors in Geosat orbits

Apparent errors in Geosat orbits are estimated directly from the measurements. There are technical difficulties in such estimates from quasi-periodically gapped data. The dominant orbit errors display a line spectrum, in which the once/orbit error peak is split in a complex way into a series of narrow lines, with other errors being present as well. The spatial pattern of the errors is not random, displaying differences between mean ascending and descending orbits which are coherent over thousands of kilometers. Orbit errors do not decorrelate within a few orbit periods.