Summary
The TotCal / CryoVExANT2011 project is an Australian and German collaboration that contributes to the validation of the CryoSat-2 radar altimetry mission through investigations of a key portion of East Antarctica near the Australian Casey Station. The Totten Glacier is one of the highest flux outlet glaciers in East Antarctica with previous studies showing focused surface lowering (at rates > 1 m/yr) and mass loss across its highest velocity grounded region. The surface of the adjacent Law Dome has along and across-track slopes ranging from 0° to over 2°. Such slopes have been particularly challenging for classical radar altimeters, and the area is an excellent natural laboratory to test the performance of the advanced interferometric mode of the dual-antenna CryoSat-2 mission. We seek to contribute to the validation of four aspects of the CryoSat mission through the use of in-situ static and kinematic GPS, aircraft LiDAR and ASIRAS radar altimetry, and in-situ firn measurements. The first component of the project provides independent estimates of the signal delay due to tropospheric water vapour using our network of six in-situ GPS sites deployed in each of the past two summer seasons (2010/11 and 2011/12). Second, we will assess the SAR-In mode of the SIRAL altimeter in an area of significant across-track slope through comparison with detailed topographic data collected using airborne scanning LiDAR and detailed snowmobile-based GPS surveys. The in-situ GPS sites deployed in the region also serve to provide reference stations for the precise positioning of the aircraft and skidoo trajectories. Third, we will assess potential spatial and temporal biases on elevation retrieval by CryoSat through comparison of the airborne ASIRAS radar altimeter data with the surface as determined by simultaneous scanning LiDAR observations. We further investigate spatial variations of radar return and near surface firn properties along a transect of firn pits and corner reflectors. Finally, we aim to compare CryoSat based estimates of elevation change over a range of regions (and surface elevation rates of change) with those determined from historic surveys, previous satellite altimeters results, and recent repeat airborne LiDAR surveys. In this contribution we show initial results from processing of data collected over the 2011/12 field season, following the return of our GPS sites and related data in mid April 2012. We focus on the generation and accuracy assessment of the in situ Digital Terrain Model the covers our primary validation region on Law Dome. We present an assessment of the GPS derived aircraft trajectory of the AWI Polar-6 aircraft, as well as a comparison of surface topography derived via kinematic GPS and airborne LiDAR. Initial comparisons and assessment of the SAR-In returns over this region are provided.