Analysis of collinear passes of satellite altimeter data

Abstract

The analysis of altimetry measurements along repeated satellite ground tracks, as in the Geosat Exact Repeat Mission, provides an excellent way of determining temporal variability in the sea surface height. This collinear analysis is usually carried out in two steps: first, by determining a mean sea level profile and then by removing a radial orbit error. We propose a new unified analysis method for the simultaneous estimation of orbit error, mean sea surface height, and residual sea surface heights (variability) with respect to each pass. All passes are treated in exactly the same way; the consequent rank or datum defect in the model is overcome by appending a minimal set of conditions, chosen either to give no overall distortion of the orbits or otherwise a best fit to a reference profile, such as the geoid. Gaps in the altimeter data are easily accommodated. Numerical results of the method are shown using data from the first year of the Geosat Exact Repeat Mission. Some consideration is given to the choice of radial orbit error model. The results indicate that for orbit error removal, a sinusoid model is the most appropriate over a one‐revolution cycle. For passes less than one revolution in length, a component of the longer wavelength ocean signal is lost if using the sinusoid model. If passes longer than about two revolutions (some 200 mins) are analyzed, additional terms are needed to eliminate nongravitational perturbations.

Gravimetric Methods – Satellite Altimeter Measurements

“…The one problem with all these techniques is that they will absorb some of the real long-wavelength ocean variability in addition to the orbit error (Van Gysen et al, 1992). This is more likely when the SL variation is of the same order of magnitude as the orbit error.…”

Applied marine geodetic research in polar regions

“…Large gradients between two measurements (1 Hz) may indicate a crossing of sea ice. All orbits of the exact repeat Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 17:53 27 December 2014 mission (ERM) are then merged for a combined orbit determination by collinear analysis with least-squares adjustment, using a three parameter model (Gysen et al, 1992) to minimize the errors within one orbit:…”

Validation of empirical orbit error corrections using crossover difference differences

“…Thus in either repeat pass or crossover minimization techniques it is customary to solve for a tilt and bias or preferably a sinusoidal correction for the radial height error. Such an empirical correction is well known to reduce the radial uncertainty in the altimeter heights, although some ocean signal is absorbed into the correction [Tai, 1991;Van Gysen et al, 1992]. This study attempts to set a quantitative limit on the magnitude of absorption of such ocean signals into sinusoidal orbit error correction coefficients.…”