A New Technique for Correcting Satellite Ephemeris Errors Indirectly Observed from Radar Altimetry.
Abstract
After high-frequency, temporal, and environmental effects have been removed from satellite radar-altimetry measurements, ephemeris (and other low-frequency) errors still remain. The vertical component of these low-frequency errors can be indirectly observed in the form of geoid height differences occurring at the satellite's ground-track intersections. This report presents a new technique for correcting these errors. The main features of the technique are that the satellite's ground-track is treated as one time-continuous track which repeatedly intersects itself and that no a priori functional form of the ephemeris errors is assumed. A conjugate gradient-projection algorithm is used to find the unbiased, discrete function of minimum weighted variation which produces the geoid height differences observed at the ground-track intersections. After inspecting the discrete solution, a suitably-chosen continuous function can be fitted to the discrete data and used to reduce the ephemeris errors. Preliminary analysis of SEASAT geoid height data has indicated that an altitude correction to an accuracy of 20 centimeters rms is possible. Although this new method is presently being applied to satellite data, the scope of the technique is much wider than this. The algorithm can be employed to reduce any time-dependent, low-frequency error present in network-type surveys (e.g., oceanographic shipboard and airborne surveys). Future applications include the removal of the diurnal variation present in magnetic surveys and the removal of the nonlinear gravimeter drift present in gravity surveys. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1981
- Accession Number
- ADA102875
Entities
People
- James R. Cloutier
Organizations
- Naval Oceanographic Office