Frozen orbits and their application in satellite altimetry
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For several instrumental reasons, not further to be discussed in this note, there is a desire to minimize the height variations of an altimeter satellite with respect to the mean sea surface. Intuitively one would assume that this is accomplished by minimizing the mean eccentricity of an orbit. However in reality frozen orbits are chosen by which the mean eccentricity significantly differs from zero. It turns out for GEOSAT and SEASAT that it is possible to fix the mean value of the argument of perigee at approximately 90° with a mean eccentricity of about 10−3. In this case the orbit is trapped in deep resonance, a theory originally developed for the odd m=0 coefficients of the gravity field by Cook (1966). On basis of this theory we will discuss the use of frozen orbits in satellite altimetry. We will also point out that Cook’s theory may be extended easily to deep resonant perturbations caused by m≠0 for orbits with repeating ground tracks. Moreover, we will address some difficulties in observing long periodic, large scale effects from satellite altimeter data.
KeywordsGravity Field Gravity Model Satellite Altimetry Potential Coefficient Initial State Vector
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