The Envisat Asar Instrument Verification and Characterisation

The ENVISAT Advanced Synthetic Aperture Radar (ASAR) is a sensor of paramount importance for the remote sensing community. Its enhanced flexibility with respect to the ERS AMI gives a wide combination of different spatial resolutions, incidence angles, swath width sizes and polarisation diversity, which are reflected in an increased number of operational modes for a large set of scientific and operational applications. Its advanced design based on the use of an active antenna, with individual subarray temperature compensation and internal calibration loop, is complex but a breakthrough with respect to the experienced passive antenna design concept. This paper describes the verification and characterisation process of the ASAR instrument from equipment level up to instrument level, the test philosophy throughout the assembly and integration activities, in both aspects. the qualification for the ENVISAT mission and the characterisation to guarantee, as well as enhance, the ASAR instrument performances. A summary of the qualification results and a performance analysis of the characterisation test data is also given.