Sea‐state‐related altitude errors in the SEASAT radar altimeter

For the work reported here, a six‐parameter model waveform is least squares fitted to 10‐s averages of the data from the 63 waveform sampling gates in the SEASAT radar altimeter. One of the fitted parameters is a time‐origin parameter that provides a measure of the position of the actual mean radar waveform relative to the sampling gate set and thus provides a correction to the instrument's altitude measurement. For the data set analyzed this correction appears to vary quadratically as a function of the significant waveheight (SWH). The result to date is that the correction Δ G , in centimeters, which should be added to the surface elevation measurements on the SEASAT geophysical data record (GDR), is given by Δ G = 0.593 S G + 0.476 S G 2 where S G is the GDR value for SWH, in meters. The discussion in this paper reviews waveform assumptions built into the SEASAT onboard altitude tracker and subsequent altitude data processing and lists several additional important effects that were not included in that processing but which are incorporated into the SEASAT waveform analysis reported here.