Abstract
Abstract. Elevation measurements of the continental water surface have been poorly collected with in situ measurements or occasionally with conventional altimeters with low accuracy. Techniques using InSAR at near-nadir angles to measure the inland water elevation with large swath and with high accuracy have been proposed, for instance, the WSOA on Jason 2 and the KaRIn on SWOT. However, the WSOA was abandoned unfortunately and the SWOT is planned to be launched in 2021. In this paper, we show real acquisitions of the first spaceborne InSAR of such kind, the Interferometric Imaging Radar Altimeter (InIRA), which has been working on Tiangong II spacecraft since 2016. We used the 90-m SRTM DEM as a reference to estimate the phase offset, and then an empirical calibration model was used to correct the baseline errors.
Highlights
For several decades, ocean topography measurements of radar altimeters have been collected, but very poor data over global inland waters are known
It works at Ku band and on an orbit height of 400 km with an interferometric baseline length of 2.3 m and an inclination angle of 5 degree
The interferometric calibration was done in two steps after common interferometric processings were performed, such as the coregistration, the interferometric phase calculation, the phase unwrapping, and the phase-to-topography conversion
Summary
Ocean topography measurements of radar altimeters have been collected, but very poor data over global inland waters are known. Spaceborne near-nadir interferometric SAR (InSAR) at Ku or Ka band has been an important evolution for conventional radar altimeters, which extends the elevation measurements from over mere oceans to including inland water bodies (Biancamaria et al 2016), such as lakes, reservoirs, rivers, and wet lands, etc. Those near-nadir InSARs can give measurements of ocean surface topography and inland water surface elevation with two-dimensional extended area rather than one-dimensional profile of conventional radar altimeters. Assessment of acquisitions over oceans can be found in (Kong et al 2017)
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