Cross-track and proposed multi-frequency SAR interferometry: comparisons with optical holographic interferometry

This article points out that the principles of the synthetic aperture radar (SAR) interferometer operating in the cross-track mode and the proposed multi-frequency SAR interferometer are equivalent respectively to those of multi-source and multi- wavelength optical holographic interferometry. Expressions are derived to describe the loss of coherence by various factors. Including the temporally and spatially random as well as deterministic changes in complex reflectivity; and their relative importance is discussed for both the SAR interferometers. The similarities of the decorrelation effect between the SAR interferometers and laser speckle are mentioned. The authors also show that the extracted phase from the cross-track SAR interferometer data does not faithfully represent the range-varying surface height variation. The effect is due to the fact that the holographic principle is applied only to azimuth direction