Residual errors in altimetry data detected by combinations of single- and dual-satellite crossovers |
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| Authors: | J Klokočník C A Wagner J Kostelecký |
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| Institution: | (1) Astronomical Institute, Czech Academy of Sciences, Ondřejov Observatory, CZ-251 65 Ondřejov, Czech Republic e-mail: jklokocn@asu.cas.cz, CZ;(2) NOAA, 1305 East–West Highway, Silver Spring, MD-20910, USA, US;(3) Faculty of Civil Engineering, TU Prague, Thákurova 7, CZ-160 00 Prague 6 and Research Institute of Geodesy, CZ-250 66 Zdiby, Czech Republic, CZ |
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| Abstract: | The single- and dual-satellite crossover (SSC and DSC) residuals between and among Geosat, TOPEX/Poseidon (T/P), and ERS
1 or 2 have been used for various purposes, applied in geodesy for gravity field accuracy assessments and determination as
well as in oceanography. The theory is presented and various examples are given of certain combinations of SSC and DSC that test for residual altimetry data errors, mostly of non-gravitational origin, of the order of a few centimeters.
There are four types of basic DSCs and 12 independent combinations of them in pairs which have been found useful in the present
work. These are defined in terms of the `mean' and `variable' components of a satellite's geopotential orbit error from Rosborough's
1st-order analytical theory. The remaining small errors, after all altimeter data corrections are applied and the relative
offset of coordinate frames between altimetry missions removed, are statistically evaluated by means of the Student distribution.
The remaining signal of `non-gravitational' origin can in some cases be attributed to the main ocean currents which were not
accounted for among the media or sea-surface corrections. In future, they may be resolved by a long-term global circulation
model. Experience with two current models, neither of which are found either to cover the most critical missions (Geosat &
TOPEX/Poseidon) or to have the accuracy and resolution necessary to account for the strongest anomalies found across them,
is described. In other cases, the residual signal is due to errors in tides, altimeter delay corrections or El Ni?o. (Various
examples of these are also presented.) Tests of the combinations of the JGM 3-based DSC residuals show that overall the long-term
data now available are well suited for a gravity field inversion refining JGM 3 for low- and resonant-order geopotential harmonics
whose signatures are clearly seen in the basic DSC and SSC sets.
Received: 15 January 1999 / Accepted: 9 September 1999 |
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| Keywords: | : Satellite altimetry – Single and dual crossovers – Student-t statistics |
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