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Oceansat-2 and ScatSat Scatterometer Enhanced Resolution Image Products (version 0)

Oceansat-2 carried the OSCAT-1 scatterometer and ScatSat-1 caried the OSCAT-2 scatterometer. The wide swath and frequent overflights permit generation of a wide variety of OSCAT Image products. The similarity of QuikSCAT and OSCAT-1/-2 means that the OSCAT can be viewed as continuity missions for QuikSCAT. (Note, however, that OSCAT measurements are at a slightly different incidence angle, which produces different sigma-0 values. No incidence angle correction is applied in OSCAT SCP version 0 images.) 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.

Images are made both from the OSCAT footprint ("egg") backscatter measurements and from the "slice" measurements. Generally, slice measurements yield higher spatial resolution but are noiser than egg measurements. The nominal image pixel resolution for egg images is 4.45 km/pixel while the nominal image pixel resolution for slice images is 2.225 km/pixel.

Further information is available in the OSCAT Enhanced Resolution Image Users Notes.

The OSCAT SIR and AVE images are produced from OSCAT Level-1B (L1B) products produced by ISRO. The L1B files available from ISRO were produced using several different software versions. These reflect improving calibrations, but there are inconsistencies between versions.
Time periodProcessor
JD 309, 2009 - JD 015, 20101.2
JD 016, 2010 - JD 181, 20101.3
JD 182, 2010 - JD 273, 2010no data
JD 274, 2010 - JD 147, 20131.3
JD 148, 2013 - Present1.4

At present the SCP is not making corrections to the L1B files to correct inconsistencies between the versions of the L1B processor. Users shoud take care when using images that span boundaries between procesor versions.

As reprocessed L1B data becomes available, current SCP products will be updated with the most recent version available.

Available Image Classes
Egg Images
  H Pol V Pol
all passes+ oueh ouev
ascending passes only++ oaeh oaev
descending passes only++ odeh odev
morning passes* omeh omev
mid-day passes** oneh onev
evening passes*** oeeh oeev
Slice Images
  H Pol V Pol
all passes+ oush ousv
ascending passes only++ oash oasv
descending passes only++ odsh odsv
morning passes* omsh omsv
mid-day passes** onsh onsv
evening passes*** oesh oesv

* Only Ant region
** Only Arc, Grn, and NHe regions
*** Only Ant, Arc, Grn, and NHe regions
+ sea ice masks are in ouev and ousv, Ant and Arc
++ non-polar regions only

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.

NOTE: ISRO-reported calibration of OSCAT products are used in this product even though the calibration is known to be imperfect. No corrections or cross-calibration with other scatterometers has been applied to the image data. A future release will include calibration corrections.

OSCAT products are produced in the same way and on the same grids as QuikSCAT products, so the same tools can be used. Note that OSCAT is at a slightly different incidence angle than QuikSCAT.