Ers-envisat Tandem Cross-interferometry for Monitoring of Sea Ice

The very short temporal separation (about 28 minutes) of the ERS-2 and ENVISAT satellites is very attractive to obtain almost-simultaneous acquisitions, appealing for SAR Interferometric applications both for the very high temporal correlation, for the strong reduction of atmospheric artefacts, and for monitoring fast displacements. The problem of the interferometric combination of such data arises from the difference of 31MHz in the Centre Frequency of the AMI (ERS-2) and ASAR (ENVISAT) instruments. This difference, overcoming the range bandwidths of the instruments (respectively 15.5 and 16Mhz), results in completely uncorrelated range spectra of the two acquisitions, and hence in no possible interferometric combinations, if not for close-to-ideal point targets. The European Space Agency has carried out in the last years a number of ad-hoc EET Campaigns with a specific orbit configuration with a normal baseline between ERS and ENVISAT of around 2.1 Km, tuned according to the principles shown in [1] to compensate the Centre Frequency shift and to allow interferometric combination of the data, at least in areas with moderate slope of the topography.