MONITORING OF SEA ICE DYNAMIC BY MEANS OF ERS-ENVISAT TANDEM CROSS-INTERFEROMETRY Paolo Pasquali (1) , Alessio Cantone (1) , Massimo Barbieri (1) , Marcus Engdahl (2) (1) sarmap s.a., cascine di Barico, 6989 Purasca, Switzerland, Email:paolo.pasquali@sarmap.ch (2) ESA/ESRIN, via Galileo Galilei, 00044 Frascati, Italy, Email: Marcus.Engdahl@esa.int ABSTRACT The interest in the monitoring of sea ice masses has increased greatly over the past decades for a variety of reasons. These include: - Navigation in northern latitude waters; - transportation of petroleum; - exploitation of mineral deposits in the Arctic, and - the use of icebergs as a source of fresh water. The availability of ERS-Envisat 28minute tandem acquisitions from dedicated campaigns, covering large areas in the northern latitudes with large geometrical baseline and very short temporal separation, allows the precise estimation of sea ice displacement fields with an accuracy that cannot be obtained on large scale from any other instrument. This article presents different results of sea ice dynamic monitoring over northern Canada obtained within the “ERS-Envisat Tandem Cross-Interferometry Campaigns: CInSAR processing and studies over extended areas” project from data acquired during the 2008-2009 Tandem campaign.. 1. INTRODUCTION 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 correlation (possibly resulting in very precise DEMs), 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. As shown in 0, 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 combination, if not for close-to- ideal point targets. The European Space Agency has carried out in the last years two ad-hoc EET Campaigns with a specific orbit configuration of 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 allow interferometric combination of the data, at least in areas with moderate slope of the topography. Data acquired with this configuration is hence of particular interest for monitoring fast displacement of sea ice in the northern regions. 2. DATA AVAILABILITY ESA has carried out the second EET campaign in the period November 18 th 2008 – April 7 th 2009. A summary of the resulting available frames suitable for Cross-Interferometry is shown in Figure 1 for the northern latitudes in the American continent. Figure 1. Availability of ERS-ASAR frames over the northern latitudes from the second EET campaign. Here only the frames that correspond to ERS-ASAR pairs with proper baseline area shown. Furthermore, the screening discarded also the pairs that are characterised by small difference of the Doppler Centroid. This condition is necessary to discard all the acquisitions characterised by too large values of the Doppler Centroid in the ERS acquisition, case that happens quite often in the current gyro-less functioning mode of the ERS-2 platform. From Figure 1 it is possible to notice how some areas of this region are particularly well covered, like the areas of the Beaufort and Baffin seas. Furthermore, thanks to the large overlap at these latitudes of the ground tracks and to the duration of the campaign of more cycles, many areas are covered more than once during the campaign, allowing to compare results obtained at _____________________________________________________ Proc. ‘Fringe 2009 Workshop’, Frascati, Italy, 30 November – 4 December 2009 (ESA SP-677, March 2010)