Theory and Design of Time-series Sar (tsar) Systems

InSAR has proven to be a very versatile for the measurement of Earth surface topography, displacement, and volume structure. In the past 20 years since InSAR has become useful, the community has developed many capabilities to exploit single interferograms for the above and other applications. Current research is moving towards the next logical step in InSAR capability—extending the measurement modality from three dimensions to four, and present the temporal variability of surface change. Most current spaceborne SAR systems are designed with repeat orbits to image terrain repeatedly and consistently, and NASA’s studies to develop DESDynI and other radars are aimed at enabling time-sensitivity. Two common techniques, persistent scattering (PS) and small baseline subset analysis (SBAS), provide the needed time series data. Here we model these and other temporal techniques with the goal of accurately describing their performance based on system parameters, and orbital and imaging geometries. This allows us to properly choose between the several radar systems now in use for a given application, and perhaps more importantly, design new spaceborne systems to enable specific studies and uses. We process several data sets collected by the various instruments in orbit today, and find that the accuracy of the radar image time series varies from cm to several mm radar line-of-sight measurements. Finally, we examine several possible designs for the NASA DESDynI mission and tabulate the expected level of performance for various surface conditions.