ASCAT Ground Processor Prototype The Ground Processor Prototype
(GPP) allows the raw science data generated by the instrument to
be converted into three sets of radar backscatter values from
which the wind field can be deduced. The Advanced Scatterometer
(ASCAT) system architecture is shown in the figure below.
Initially in the ground processor, corrections are made for
receiver noise and instrument gain variations. This includes
both internal calibration correction (for power gain variations)
and external calibration correction for the antenna patterns.
The corrected power spectra are then converted into raw (radar
backscatter) sigma-naught values using normalisation look-up
tables. ASCAT system architecture The raw sigma-naught values
are transformed from the frequency-domain into geographical
coordinates and spatially filtered onto the grid of nodes along
each beam direction. These are aligned such that the nodes from
each of the three beams illuminating a swath are coincident,
thereby producing the sigma-