Methods for Lwir Radiometric Calibration and Characterization
نویسندگان
چکیده
The utility of a thermal remote sensing system increases with its ability to retrieve surface temperature or radiance accurately. Several applications require absolute or relative accuracies far better than 1 C. To achieve these levels of accuracy routinely, scientists must perform laboratory and onboard calibration as well as in-flight vicarious characterization, incorporating a wellcalibrated infrared radiometer that is mounted on a buoy and placed on a uniform water body. The radiometer monitors the water surface radiant temperature. Combining this measurement with atmospheric pressure, temperature and water vapor profiles, a topof-the-atmosphere radiance estimate can be calculated with a radiative transfer code to compare with the sensor’s output. On very still waters, however, a buoy can significantly disturb these measurements. Scientists at NASA’s Stennis Space Center (SSC) have developed a novel approach, using an uncooled infrared camera mounted on a boom, to quantify buoy effects. Another critical aspect of using boom-mounted infrared radiometers is the need for extensive laboratory characterization of the instruments’ radiometric sensitivity, field of view and spectral response. Proper water surface temperature also requires a detailed knowledge of both the upward emission and reflected sky emission. Recent work at SSC has demonstrated that the use of a polarization-based radiometer, operating at the Brewster angle, can simplify temperature retrieval as well as improve overall accuracy. * Corresponding author.
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