Validation of along-track interferometric SAR measurements of ocean surface waves

C-band HH-polarized along-track interferometric synthetic aperture radar (A TInSAR) images of ocean waves from the Canada Centre for Remote Sensing (CC RS) CV-580 SAR are used to study ATInSAR wave imaging fidelity. ATInSAR pha se spectra are derived using cross spectra between the interferogram phase generated from individual look complex SAR images. The resulting observed p hase spectra are quantitatively compared with forward-mapped in situ direct ional wave spectra collocated with the ATInSAR observations, The forward ma pping models include two quasilinear forward transforms that include varyin g degrees of velocity bunching nonlinearity, both of which include an azimu th null in the modulation transfer function, and an implementation of the f ully nonlinear forward transform, The null arises from the cancellation of upward and downward orbital velocity components within a resolution cell. T he second of the two quasilinear transforms and the nonlinear forward trans form are shown to have agreement with the observed velocity spectra, as mea sured by correlation coefficients between the observed spectra or forward-m apped spectra and the ATInSAR spectra, ATInSAR can allow a direct measureme nt of the orbital velocity spectrum, There is, however, an added layer of c omplexity caused by the cancellation of upward and downward orbital velocit y components within a resolution cell. Furthermore, the SAR complication of velocity bunching nonlinearity is not avoided by using an ATInSAR.