SAR-mode altimetry performance over the Antarctic ice sheet

Jérémie Aublanc (CLS, France)

CoAuthors

Thomas Moreau (CLS, France); Pierre Thibaut (CLS, France); Francois Boy (CNES, France); Nicolas Picot (CNES, France); Frederique Remy (LEGOS, France); Denis Blumstein (LEGOS, France)

Event: 2016 SAR Altimetry Workshop

Session: Applications, SAR for science

Presentation type: Type Oral

During the past 30 years, Earth’s polar region has been continuously monitored by satellite altimetry. Thanks to their wide spatial coverage and relatively high temporal sampling, radar altimeters have greatly improved our knowledge of the ice-sheets topography and our understanding of the ice sheets dynamics. Over that time period, all radar altimeter missions flying over ice-sheet surfaces (GeoSat to Altika) have been operating in conventional Low Resolution Mode (LRM). Despite constant improvements in resolution and precision, LRM instruments still suffer from several limitations and uncertainties, notably due to their large radar footprint: 10km to 20km (depending on mission).
Unlike its predecessors, the Cryosat-2 and Sentinel-3A satellites carry on-board a new generation of radar altimeter instrument operating in a Synthetic Aperture Radar (SAR) mode. This mode allows to reduce the along-track resolution to 300 meters, that would make it possible to capture finer-scale topographic variations of ice-sheet surfaces. The SAR-mode performances have been thoroughly analyzed in open ocean with Cryosat-2 data. However their abilities in monitoring of ice-sheet surfaces have still to be assessed.
SAR-mode radar altimeter data have been recently analyzed over the Antarctica continent, with sporadic Cryosat-2 acquisitions performed in winter 2014 and Sentinel-3A SRAL data acquired in spring 2016. Those data have been processed through the CNES prototype chains (the CPP for Cryosat-2 and the S3PP for Sentinel-3A) and the use of innovative and dedicated algorithms to this particular surface. This paper presents a comprehensive study of the SAR-mode performance over ice-sheet surfaces in comparison with LRM one, focusing on analyses of the waveform shapes, the accuracy of the retrieved surface elevation , its sensitivity to surface slope and penetration effects into the snow/ice layers. This work clearly demonstrates the improved ice-sheet surface measuring capability offered by SAR-mode altimetry with respect to conventional radar altimetry.
 

Oral presentation show times:

RoomStart DateEnd Date
Auditorium Mon, Oct 31 2016,16:15 Mon, Oct 31 2016,16:30
Jérémie Aublanc
CLS
France
jaublanc@groupcls.com