Analysis of 1.4 GHz Radiometric measurements from Skylab

Results from the 1.4 GHz, S-194, microwave radiometer located on the SKYLAB satellite are presented. The objective of the investigation is to establish the degree to which quantitative measurements of sea surface temperature, salinity and related marine wind fields can be made using the S-194 radiometer. The analysis of the S-194 data demonstrates that it is possible to make measurements of the brightness temperature of open ocean areas with an RMS absolute accuracy of ±1.3 K over a wide range of environmental conditions. The S-194 is relatively insensitive to sea surface temperature changes and, even though measurements are available over a range in sea surface temperature of 30°C, no significant change in the measured antenna temperature was detected. However, S-194 is relatively sensitive to changes in surface salinity; and the analysis of data taken over the open ocean shows that salinity can be determined to an accuracy of ±2 parts per thousand. Further, it is shown that is it possible to accurately model complex regions such as lakes and bays, where a significant portion of the antenna beam is filled by land, and obtain excellent agreement between calculated and measured antenna temperatures. Open ocean measurements, obtained over the wide range in winds speeds of from 0 to 48 knots, show the antenna temperature to be weakly, but unambiguously, correlated with wind speed. The wind speed dependence determined, of 0.16 K/knot, indicates that surface wind speed can be measured to an accuracy of ±8 knots using the S-194.