Preliminary Geophysical Evaluation of the Visible and Infrared Radiometer (VIRR) on Seasat-A

Although the VIRR was only operative for the first 60 days of SeaSat-A\´s lifetime of 99 days, the quality of the measurements collected appears generally to be very good. The grided visual and thermal infrared images are quite adequate for meeting the objectives of cloud, land, and water feature identification, and a number of scene-specific enhancement options can be exercised. The noise levels in the VIRR data except for occasional small groups of adjacent scan lines, appear to be comparable to the digitization resolution (about C for the infrared measurements). Statistical analysis of a sample of 139 points in a large cloud free region of the western North Atlantic on 7 July 1978 yielded a mean difference of C, a root mean square difference C and a linear correlation coefficient of 0.84 between VIRR sea surface temperature estimates and those interpolated from a NOAA analysis based on ship, buoy, and XBT observations for the period 5-10 July 1978. This is very good agreement in view of the uncertainties in the atmospheric correction to the VIRR brightness temperatures and those in the smoothed NOAA field.