Onera Campaign in South Greenland for Imaging of Snow/Ice Subsurface Features from Airborne SAR
Résumé
An acquisition campaign of the ONERA airborne synthetic aperture radar system RAMSES have been set up on the the Greenland ice-shelf to assess the detectability of buried object and subsurface features through dry snow/ice cover. Three bands where investigated UHF, L and X band expecting a tradeoff between cover penetration and target radar cross-section, the latter being critical due to the expected high clutter radar cross-section. Four sites were imaged, a calibration zone and a front glacier close to Kangerlussuaq, a dry accumulation zone North of the polar circle, a percolated accumulation zone East of Narsassuaq, and an intermediate zone between accumulation and ablation zone. The engine fragment plume of the unconfined engine #4 failure of the F-HPJE (about 190 days earlier) was in the middle of the percolated accumulation zone, providing several known buried fragments, as well as opportunities to unravel unknown buried fragments that may have an interest for the engine failure investigation. Test objects (corner reflectors, Luneburg lens, ice filed plastic sled, snow refilled hole) have been setup at known positions and depths to assess detection through cover and ice drift rates. Processing of the data confirmed the high clutter return, the better penetration at low (UHF) band and the higher radar cross-section at high (X) band. However, the setup targets radar cross-section presented an unexpected considerable attenuation that prompted the use of X-band and intensive processing to detect buried targets.
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