Multichannel surface clutter suppression: East Antarctica P-band SAR ice sounding in the presence of grating lobes

• Published in: Annals of Glaciology
• Main Authors: Bekaert, David, Gebert, Nicolas, Lin, Chung-Chi, Heliere, Florence, Dall, Jørgen, Kusk, Anders, Kristensen, Steen Savstrup
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: GEOGRAPHY; GEOSCIENCES; SHEETS; Antarctic glaciology; ground-penetrating radar; ice streams; remote sensing; Antarctic; East Antarctica; Jutulstraumen; Jutulstraumen Glacier; Annals of Glaciology; Antarc*; Antarctica
• Online Access: https://orbit.dtu.dk/en/publications/65669372-5958-4124-a708-b3d16279bb51; https://doi.org/10.3189/2014AoG67A100

Ice sounding with radar is a well-established technique for the retrieval of ice depth, and provides information on ice structures and layering. Airborne radar ice sounders suffer from off-nadir surface clutter that masks the signal from bedrock and ice layers with unwanted but simultaneously received surface reflections. This is of importance for future satellite ice-sounding missions, as the spaceborne geometry leads to strong surface clutter even for deep subsurface returns. This paper presents analysis and comparison of different clutter-suppression techniques applied to data acquired with the European Space Agency's P-band POLarimetric Airborne Radar Ice Sounder (POLARIS). The 4 m long antenna of POLARIS enables simultaneous reception of up to four across-track channels. It was operated in 2011 over Antarctica at a high flight altitude of 3200 m. Different coherent weighting techniques of the receive channels were used to suppress the surface 'clutter'. However, with a channel spacing of 1.4 times the wavelength, the grating lobe imposes a limitation to the off-nadir angular range in which clutter can be effectively attenuated. Results of ice sounding over Jutulstraumen glacier are described, where we demonstrate a clutter suppression of up to 10 dB.