Temporal Decorrelation in Repeat-Pass Radar Interferometry

Ptotof = Ptemporaf ' Pspatial ' Pthermal (3) Radar interferometric techniques can be used to measure the degree of phase coherence in the complex radar returns from a target of interest acquired at different times. When an imaging platform makes several passes over a site, a number of different interferograms representing different temporal and spatial baselines can be generated. The complex backscatter from the target can then be compared for the various images, and the effects due to the spatial baselines and noise levels removed. What remains is a measure of the "decorrelation" of the radar signals with time, which is indicative of We note that this derivation incorporates an assumption that the thermal noise powers at each antenna are equal, and that it is a trivial extension of the above to account for the situation for differing noise levels. As a result, if any three of the quantities in equation (3) are known, the fourth may be determined. For data analyzed in this paper, we know quite well our imaging geometry and signal to noise ratio and can measure the total correlation ptotar, therefore the temporal component, which contains the information about the target, may be inferred. changes in the surface occuring duriig the period of time spanned by the images, The rate of this decorrelation ,,lays a critical role in the design of a repeat-pass topographic mapping mission. The exact form of the baseline decorrelation function depends both on the assumed scattering statistics of the surface and the impulse response of the system. For the typical radar model where the impulse response is