Antarctic SAR and INSAR calibration experiment during the International Polar Year

Benoit Legresy(1) , Betlem Rosich Tell(2) , Christophe Caspar(2) , Jean-Marc Lopez(3) , Jean-Claude Souyris(3) , massimo frezzotti(4) , and Frederique Remy(5)

(1) CNRS/Legos, 18 av. E. Belin, 31401 Toulouse, France
(2) ESA, Via Galileo Galilei, Frascati, Italy
(3) CNES, 18 Av. E. Belin, 31401 Toulouse, France
(4) ENEA, casaccia, roma, Italy
(5) CNRS/LEGOS, 18 Av. E. Belin, 31401 Toulouse, France


A CAL/VAL network for SAR in the central EAST Antarctica. The ERS INSAR tandem mission brang enormous new knowledge on the ice dynamics and in particular in Antarctica. Fast flowing ice streams and outlet glaciers were much better understood. The main purpose of INSAR on the ice is to measure surface velocity, topography and ice ocean interaction. ENVISAT and other single satellite SAR satellites ,though limited by the 35d (instead of 1 or 3 d with ERS1 or tandem) to observe fast flowing parts of the ice cap, offer opportunities to concentrate on inland much slower ice flow. The surface velocity reveals the dynamic state of the ice, the beginning of ice streaming, the flow boundary conditions changes like the presence of subglacial lakes, bedrock hills and mountains. Getting to know accurate velocity field at particular places like deep ice core drilling sites or regions of particular ice configuration like domes, saddles, convergence, divergence, ice divide... is of particular interest. On the Antarcic plateau, the topography is relatively smooth and well known, the atmosphere is quite clear and interferometry works relatively well. However the ice caps compounds very few rockyfixed outcrops to tie the SAR images and interferogramms and the large scale smooth ice flow frequently show ramps of parallel fringes which would be interpreted as residual orbit fringes in other land applications. This lack of tie points is the main limitation to accurate velocity measurement. The international polar year will bring a good opportunity with the TASTE-IDEA traverses which will follow the East Antarctic Ice Divide. This a unique opportunity to disseminate tie points available at the top of the ice cap where they are so crually missing. We designed a SAR corner reflector network to take advantage of the traverse. This traverse has the advantage to give central sites on te ice cap which we also choosed to be around sites of glaciological interest. It is very small accumulation and little windy positions so that the reflectors should be visible during a life time which we expect to be around 20 years. The main difficulty is to cope with the high backscatter of the area and with the difficulty to position accurately the reflector in a snowfull area. A first reflector has been sent to Tallos Dome for the 2005-2006 season and will be tested during the fronge meeting. We will show the design of the network, of the SAR reflector and the main ideas of the project.



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