Improved ocean-geoid resolution from retracked ERS-1 satellite altimeter waveforms |
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| Authors: | Stefan Maus Chris M Green & J Derek Fairhead |
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| Institution: | Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK,;GETECH, Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK |
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| Abstract: | The ocean geoid can be inferred from the topography of the mean sea surface. Satellite altimeters transmit radar pulses and determine the return traveltime to measure sea-surface height. The ERS-1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform. Tracking the time shift of the waveform gives an estimate of the distance to the sea surface. We retrack the ERS-1 radar traveltimes using a model that is focused on the leading edge of the waveforms. While earlier methods regarded adjacent waveforms as independent statistical events, we invert a whole sequence of waveforms simultaneously for a spline geoid solution. Smoothness is controlled by spectral constraints on the spline coefficients. Our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid. The coherence of repeat track solutions indicates a spatial resolution of 31 km, as compared to 41 km resolution for the ERS-1 Ocean Product. While the resolution of the latter deteriorates to 47 km for wave heights above 2 m, our geoid solution maintains its resolution of 31 km for rough sea. Retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along-track resolution. |
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| Keywords: | fractals geodesy geoid anomalies gravity Satellite Geodesy waveform analysis |
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