Evaluating interferometric baseline performances in a SAR formation flight by using relative GRACE GPS navigation solutions
Andreas Kohlhase(1) , Remco Kroes(2)
, and Simone D'Amico(1)
Münchner Str. 20,
(2) TU Delft, Kluyverweg 1, 2926 HS Delft, Netherlands
The kernel of this study is to analyze the impact of relative position errors on the interferometric baseline performance of multistatic SAR satellites flying in a close formation. Based on accuracy results obtained from differential GPS (DGPS) observations between the twin Gravity Recovery and Climate Experiment (GRACE) satellites, baseline uncertainties are derived for three interferometric scenarios of a dedicated SAR mission. For cross-track interferometry in a bistatic operational mode, a mean 2-D baseline error (1$sigma$) of 1.4 mm is derived, whereas baseline estimates necessary for a monostatic acquisition mode with a 50 km along-track separation reveal a 2-D uncertainty of approximately 1.7 mm. Absolute orbit solutions based on reduced dynamic orbit determination techniques using GRACE GPS code and carrier-phase data allows a repeat-pass baseline estimation with an accuracy down to 4 cm (2-D 1$sigma$). To assess the accuracy with respect to quality requirements of high-resolution Digital Elevation Models (DEMs), topographic height errors are derived from the estimated baseline uncertainties. The performances and thus the residual orbital phase screens are demonstrated by differencing simulated interferograms. These are calculated from baselines of distinct error signatures and magnitudes.