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ASCAT Daily Ice


Ross Ice Shelf
Weddel Sea

Ice Algorithm

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.

Enhanced resolution images made from ASCAT data are created from SZF files using the multi-variate the Scatterometer Image Reconstruction (SIR) algorithm with filtering (SIRF). Like previous fan-beam scatterometers, ASCAT collects measurements at multiple incidence angles and up to 6 azimuth angles. The effective image resolution varies depending on region and sampling conditions but is estimated to be 12-15 km in most areas. The SIRF algorithm makes "A" (sigma-0 normalized to a 40 deg incidence angle) images at 4.45 km pixel spacing for each beam. Multiple passes of the spacecraft are combined to produce a higher spatial resolution (at a cost of reduced temporal resolution). For ice imaging, the multiple beams are combined to create denser sampling, which reduces the noise level and provides the best spatial resolution. The resulting images show the normalized radar cross-section (sigma-0) in dB (10log10) at 40 degree incidence angle. No recalibration of the ASCAT data has been applied in this processing.