Using Multiple Focal Points in Fully-Focussed SAR Processing to Reduce Waveform Land Contamination

Poster (2019)

Authors

M.C. Naeije Astrodynamics & Space Missions - Aerospace Engineering
M. Kleinherenbrink Mathematical Geodesy and Positioning - CEG
D.C. Slobbe Physical and Space Geodesy - CEG
Walter Smith NOAA Laboratory for Satellite Altimetry, National Oceanic and Atmospheric Administration
P. Hoogeboom Atmospheric Remote Sensing - CEG
Research Group
Astrodynamics & Space Missions (Aerospace Engineering) (TU Delft)
More Info
expand_more

Published Date

2019

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Aerospace Engineering

Department

Space Engineering

Research Group

Astrodynamics & Space Missions

Abstract

We investigated the sensitivity of Fully-Focussed SAR
(FF-SAR) processing of CryoSat-2 altimeter data to Earth rotation and
exploit it to decontaminate waveforms in coastal zones. Earth's
rotation causes scatterers at varying cross-track locations to have a
different relative velocity with respect to the satellite. This second-order effect of Earth rotation on the phase is currently not corrected for in FF-SAR processing of altimetry data. The difference is largest near the poles, where the satellite flies parallel to the equator. We show when not
correcting for this second-order effect it yields a parabolic shape in
the counter rotated phase, which increases with the cross-track
distance. If the FF-SAR processor focusses on one point,
and there is a bright scatterer at another, then there is a residual
parabolic phase, whose sign and shape depend on the cross-track distance
and on whether the signal is left or right of the chosen focal point. In
theory, if the viewed scene only has few bright coherent scatterers,
then it might be possible to determine the cross-track position of each.
In practice though, natural targets are rarely coherent over the integration time. The
incoherent property of natural targets can, however, also be exploited
to decontaminate waveforms in coastal tracks from land signals, by
differencing two radargrams computed with two different focal points. If
the cross-track distance between the focal points is set correctly, the
speckle signal from the ocean becomes quasi-independent, while the land
signal is similar in both radargrams and can subsequently be removed.