The Envisat ASAR Mission: A Look Back at 10 Years of Operation
Miranda, N.1; Rosich, B.1; Meadows, P.J.2; Haria, K.3; Small, D.4; Lavalle, M.5; Collard, F.6; Johnsen, H.7; Monti Guarnieri, A.8; D'Aria, D.9
1ESA, ITALY; 2BAE Systems, UNITED KINGDOM; 3Telespazio Vega UK, UNITED KINGDOM; 4University of Zurich, SWITZERLAND; 5JPL, UNITED STATES; 6CLS Brest, FRANCE; 7Norut Tromso, NORWAY; 8Politecnico di Milano, ITALY; 9ARESYS, ITALY

The Advanced Synthetic Aperture Radar (ASAR) on-board Envisat operated successfully for just over 10 years until the failure of Envisat in April 2012. ASAR was ESA's very first deployment of a C-band phased-array antenna, allowing extended imaging capacity in comparison to its ERS SAR predecessors. As such it operated in various acquisition modes Image (IM), Alternating Polarisation (AP), Wide Swath (WS), Global Monitoring (GM), and Wave (WV). For IM and AP modes there was a selection of 7 swaths with swath width from 100km to 56km: IM was single-polarisation, while AP was dual-pol, offering a choice from HH&VV, HH&HV, or VV&VH. WS and GM modes had a total swath width of 405km based on the combination of 5 sub-swaths. WV acquired vignettes of 10km by 10km every 100km along the satellite track.

This paper is a look back to the 10 years of ASAR operations, covering topics such as the ASAR Instrument (characteristics, acquisition modes, product tree and observation scenario), Instrument Calibration and Performance Verification (including instrument stability, internal calibration, external calibration, absolute radiometric calibration, localisation accuracy, absolute geolocation accuracy, performance verification and product calibration), ASAR specific missions (wave and polarimetric), particular ASAR events such as antenna resets, burst synchronisation, AP swath modifications and the Envisat orbit change in October 2010.