Preliminary assessment of interferometric SAR baseline determination using DGPS

One of the challenges of a SAR interferometry mission in Low Earth Orbit is to determine with great accuracy the distances separating the satellites. The first half of the paper presents those requirements and discusses the orbital configuration for a Small Satellite SAR formation flying proposal chosen to minimize the effect of the short and long-term orbit perturbations. The second half discusses the level of precision attainable in the satellite-to-satellite baseline estimation in the absence of inter-satellite ranging data. To achieve this, GPS double differences made of only satellite-to-satellite links were simulated for three different configurations for comparison. Measurement and model noise were taken into account and the satellite parameters were recovered using in a least square estimation algorithm. The baseline is then computed and compared against a nominal "noise-free" estimate. Preliminary results shows than double difference GPS carrier phase observation are a promising method to provide the accuracy demanded.