Spatial Response
of SeaWinds Measurements
Imaging applications of SeaWinds on QuikSCAT and ADEOS II are
facilitated by applying reconstruction and resolution enhancement
algorithms to produce high resolution images of the surface normalized
radar cross section (sigma0). Such algorithms require a description
of the spatial response functions of the measurements. The pencilbeam
design of Seawinds, coupled with the onboard processing, results
in a spatial response function with varies significantly between
measurements and is a function of orbit and antenna position.
Sample
illustration of the 3 dB response contours of 'egg' (blue) and corresponding 'slice'
(red) measurements. (see other examples in the paper and in the code subdirectories)
Computing the spatial response function is complicated and requires
significant computation It requires evaluating the parameters of
the radar equation as well as detailed knowledge of the orbit geometry
and instrument processing. For this reason we have developed a method
of precomputing the response function and tabularizing it as a
function of orbit and antenna position and other necessary parameters.
For more details see the paper, I.S. Ashcraft and D.G. Long, "The
spatial response function of SeaWinds backscatter measurements",
in "Earth Observations Systems VIII", W.L. Barnes, ed., Proceedings
of SPIE Vol. 5151, pp. 609619, 36 Aug 2003. (PDF
file)
Separate tables are available for egg and slice measurements for
each instrument range gate mode and software. Egg tables
are available here while slice
tables are available here.
Software to reconstruct the simplified response function from the
tables, given the orbit and instrument parameters from the QuikSCAT
and SeaWinds L1B files, are available in both fortran and C. Some
components are available for matlab. Software is available here.
Note that the software and tables are copyright Brigham Young University,
2003. The software may be used for noncommerical purposes provided
that proper acknowledgements are made and the paper mentioned above
is cited.
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