ANTARCTIC HELD MEASUREMENTS OF RADAR BACKSCATTER FROM SNOW AND COMPARISON WITH ERS-1 ALTIMETER DATA

Two identical Ku band scatterometers were deployed at a number of loca tions in the region of the Filchner-Ronne ice shelf, Antarctica, durin g the austral summer '91/92. These were used to investigate the vertic al incidence radar properties of the top 10m of firn, and these measur ements were compared with those made by the ERS-1 radar altimeter over the region. The radar backscatter coefficient, on the ice shelf was f ound to remain constant over a period of 18 days, but the value differ ed significantly from that obtained on the nearby Coats Land plateau. Field measurements, coincident with ERS-1 overpasses, were made throug hout a 4-week field season during the three day repeat cycle of the 'I ce Phase' of the satellite's operation. These show spatial agreement w ith the ERS-1 altimeter backscatter coefficient to within 1dB. Distinc t sub-surface layering was detected at several locations, contributing up to 3dB to the total backscattered power with a variation over 30km of 1dB. The major surface factor contributing to the 7dB of spatial a nd temporal variation of backscatter coefficient, across the ice shelf , is the presence and formation of surface crusts.