Abstract
Satellite Radar Interferometry (SRI) based on SAR imagery from the European Remote Sensing Satellite (ERS-1) can detect differential changes in surface elevation on the order of centimeters (Massonnet, et al., 1993, 1994). These changes are embedded in an intermediate fringe map that depicts the pixel by pixel phase difference of the SAR beam from two repeat orbits. The phase difference results from the path length difference viewed by a stereo-pair of coherent complex SAR images, and the movement of surface and near surface active scatterers in the time interval bracketed by the repeat images. After the effect of curvature of the earth ellipsoid is removed, the residual phase difference reflects the surface deformation provided that the spatial separation between the orbits is on the order of meters, or the surface is flat. Otherwise, a terrain correction is necessary. Additional corrections bring the accuracy of orbit separation from ±3 meters, as determined by the accuracy of the restituted state vector measurements, to at least ±0.5 meters, and remove errors caused by variations in the along track elevation. The final interferogram reflects one or more of several components in surface deformation. Examples of the fast ice near Prudhoe Bay in January 1992 shown here display a dense, colorful fringe pattern indicating deformation. Discontinuities in the pattern which are up to tens of kilometers long reflect cracks that separate the fast ice into discrete segments which underwent either compression or tilting between satellite passes. Areas where the fast ice remained stationary and was probably grounded can also be identified.
