Marine & Environmental Sciences Faculty Reports

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Satellite altimetry, Short-arc mode, Spherical harmonics, Geoid undulations, Orbital integrator, Sea surface effects, Equilibrium tide, Tidal arguments, Long-period constituents, Diurnal constituents, Semidiurnal constituents, Tidal gauge


This study is a part of the on-going effort aimed at improved determinations of the earth's gravity field through the adjustment of satellite altimeter data in the short-arc mode. Until recently the key role in such adjustments has been played by GEOS-3 altimeter data. However, SEASAT altimetry is envisioned as providing a more accurate means for addressing this task.

In view of the improved quality of altimeter data and of the corresponding more stringent requirements for the data reduction, several improvements in the existing altimetry model have been designed and are described herein. For example, the criteria have been established specifying the maximum and the minimum allowable lengths of SEASAT arcs. An important improvement in the economy has been achieved through a reduction in the number of spherical-harmonic potential coefficients entering the orbital integrator, without a noticeable compromise in the excellent quality of the SEASAT observational system.

In a parallel development, the satellite aItimetry model has been improved by allowing for the inclusion of certain sea surface effects. The most important in this respect are the tidal effects (long-period, diurnal and semidiurnal), which are now subject to adjustment within the overall adjustment of SEASAT altimetry. Other effects can be included in the form of corrections to altimeter measurements. This development continues along several lines, such as adjusting a greater number of tidal constituents, or adjusting the tidal phases in addition to their amplitudes.

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Scientific Report No. 3