ANALYSIS OF ENVISAT RA-2 BURST ECHOES OVER INLAND WATER

摘要

The EnviSat altimeter during its long mission has amassed a huge database of altimeter echoes. The normal along-track sampling rate for EnviSat is 18Hz, however, EnviSat has the added capability of providing data over the underlying surface at the full 1800Hz for one second every 3 minutes. These ‘Individual Echoes’ [1] can be studied with no waveform averaging over topographic surfaces because the instrument noise is very low[2]. Analysis of the waveform shape allows identification of areas of inland water, with small targets identifiable from only one ‘clean’ echo. These bursts are gathered over a wide variety of lakes, inland seas and rivers. Over smaller water bodies, the surrounding terrain often impacts the waveform shape, and these composite echoes can be identified and filtered out. These bursts are globally distributed, and the orbit of EnviSat, with only a ±1k deadband, allows for colocation of bursts over repeat cycles.