Snow Parameter Estimation Using Multiple Squint Differential In-SAR: A Potential Application for the Harmony Mission

Abstract:
Spaceborne differential SAR interferometry for snow water equivalent (SWE) change measurements is known to be limited by: i) low coherence areas resulting from temporal decorrelation, largely complicating a robust phase unwrapping, ii) inaccurate density estimates introducing systematic errors in the phase-to-SWE inversion, and iii) an unknown phase offset due to the 2pi ambiguity of the interferometric measurement and therefore a strongly biased SWE estimate. This paper presents strategies to overcome these shortcomings by exploiting simultaneously acquired interferograms with different squint angles. The phase difference between the interferograms may be exploited to resolve the 2pi phase ambiguity of the single interferogram. In addition to that, the ratio between the interferograms is a measure of the dielectric permittivity of the snow and can be related to the snow density. The performance of the strategies is evaluated for ESA’s Harmony mission, demonstrating great potential of the approach given the large squint diversity of the Harmony constellation.