GEOGRAPHICAL REPRESENTATION OF RADIAL ORBIT PERTURBATIONS DUE TO OCEAN TIDES - IMPLICATIONS FOR SATELLITE ALTIMETRY

In analogy to the geographical representation of the zeroth-order radial orbit perturbations due to the static geopotential, similar relationships have been derived for radial orbit perturbations due to the ocean tides. At each location these perturbations are seen to be coherent with the tide height variations. The study of this singularity is of obvious importance to the estimation of ocean tides from satellite altimeter data. We derive analytical expressions for the sensitivity of altimeter derived ocean tide models to the ocean tide force model induced errors in the orbits of the altimeter satellite. In particular, we focus on characterizing and quantifying the nonresonant tidal orbit perturbations, which cannot be adjusted into the empirical accelerations or radial perturbation adjustments commonly used during orbit determination and in altimeter data processing. As an illustration of the utility of this technique, we study the differences between a TOPEX/POSEIDON-derived ocean tide model and the Cartwright and Pay 1991 Geosat model. This analysis shows that nearly 60 percent of the variance of this difference for M(2) can be explained by the Geosat radial orbit error due to the omission of coefficients from the GEM-T2 background ocean tide model. For O-1, K-1, S-2, and K-2 the orbital effects account for approximately 10 to 40 percent of the variances of these differences. The utility of this technique to an assessment of the ocean tide induced errors in the TOPEX/POSEIDON-derived tide models is also discussed.