Evaluating interferometric baseline performances in a close formation flight by using relative GRACE GPS navigation solutions

Abstract

In this paper the impact of relative position errors on the interferometric baseline performance of multistatic Synthetic Aperture Radar (SAR) satellites flying in a close formation is analyzed and assessed. 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. To assess the accuracy with respect to quality requirements of high-resolution DEMs, topographic height errors are derived from the estimated baseline uncertainties. The analysis reveals that the induced low-frequencymodulation (height bias) fulfills the relative vertical accuracy requirement (std. dev. less than 1 m linear point-to-point error) of a Digital Terrain Elevation Data model of level 3 (DTED-3) for most of the baseline constellations. DGPS can be used as an operational navigation tool for high-precise baseline estimation if a geodetic-grade dual-frequency spaceborne GPS receiver is assumed to be the primary instrument onboard the SAR satellites. To exemplarily demonstrate the error propagation into the inteferogram Orbital Phase Screens (OPS) are generated by differencing simulated interferograms. These are calculated from baselines of distinct GRACE error signatures and magnitudes.