|The fan-beam ASCAT scatterometer provides measurements
radar backscatter at 6 azimuth angles and a diversity of incidence angles.
The wide swath and frequent overflights permit generation of a wide variety
of ASCAT Image products. For highest possible spatial resolution, multiple
orbit passes are combined. These are the 'all pass' images. Since generally
orbit passes of a given point on the Earth occur at nearly the same time
of day, time-of-day studies are facilitated by computing images from ascending
(morning) passes only, and descending (evening) passes only.
For improved temporal resolution in the polar regions, daily
local-time-of-day images have been generated. In non-polar regions
ascending/descending images are produced. To ensure adequate spatial coverage
and overlap to enable B image estimation, except at the poles, generally
multiple days are combined.
Images are made from ASCAT L1B SZF files which are analogous to
SeaWinds "slice" measurements.
Further information is available in the ASCAT
Enhanced Resolution Image Users Notes.
Images are produced in the BYU .SIR file
format using the standard naming scheme.
The files are gzipped to minimize storage and transfer requirements. The
standard images are designed for land and ice observation. Data over the
ocean is generally not useful. However the distributed images are not land
masked. .SIR format land mask files (containing 0 for ocean and 1 for land)
are available for each standard region. .SIR format images containing "images"
of the latitude and longitude of each pixel for each region are also available.
Available Image Classes
|ascending passes only+
|descending passes only+
+ Non-polar regions only
* Only Ant, Arc, and Grn regions
** Only Ant region
*** Only Arc and Grn regions