The Grand Banks ERS-1 synthetic aperture radar (SAR) wave spectra vali
dation experiment took place over a study site in which intensive in s
itu wind and wave measurements were being taken. The unique aspect of
the program was the nearly simultaneous acquisition (in space and time
) of spaceborne (ESA ERS-1) and airborne (CCRS CV-580) SAR imagery of
the same ocean wave field. Although both SARs were operating at C-band
with VV polarization, the geometry of acquisition was quite different
. For example, the range-to-velocity ratio parameter was large for ERS
-1 (RN approximately 115 s) and relatively small for the CV-580 (RN <
50 s). Thus, the SAR image spectra derived from ERS-1 are significantl
y more susceptible to velocity bunching non-linearity and azimuth spec
tral cut-off, which are well-known limitations of SAR in accurately me
asuring azimuth-travelling ocean waves. Airborne and spaceborne SAR me
asurements of ocean waves are presented and compared with directional
wave buoy measurements. A technique is developed to estimate the azimu
th spectral width based upon a quasi-linear ocean-to-SAR transform, an
d is applied to all of the SAR spectra. This quasi-linear transform is
qualitatively assessed by forward-mapping directional wave buoy spect
ra into SAR image spectra. The width measurements are correlated with
observed values for the significant wave height or the azimuth shift a
nd the local wind speed. This allows definition of a quasi-linear tran
sform that includes both velocity bunching decorrelation effects and w
ind speed-dependent coherence time effects. Finally, a new SAR spectra
l inversion scheme, based upon the quasi-linear transform, is demonstr
ated. Wave model spectra are used as the starting point and validation
is against directional wave buoy spectra.