Tracking nonuniformity in the thermal infrared sensor through pre-launch measurements and simulated on-orbit data

摘要

The Thermal Infrared Sensor (TIRS) will continue thermal band measurements of the Earth for the Landsat Data Continuity Mission (LDCM). The instrument is a dual-channel, push-broom imager that consists of 1850 detector elements per band spanning the 15-degree cross track field of view. The push-broom configuration of the instrument presents several challenges to ensure that the instrument meets uniformity and linearity requirements across the field of view. Each detector element may have a slightly different spectral and radiometric response resulting from variations in pixel-to-pixel gain, bias, and spectral band shape. These differences must be measured and corrected for in order to provide a radiometrically accurate data product necessary for the Landsat science mission. During pre-launch testing, calibration ground support equipment (CGSE) is used to uniformly illuminate the TIRS field of view with various source radiances. Calibration routines are created to convert the raw detector signal from these uniform sources into accurate at-sensor radiances. During the on-orbit life of the instrument, vicarious calibration techniques such as the side-slither method may be used to check the pixel-to-pixel uniformity. To demonstrate the value of this technique for TIRS, the Digital Imaging and Remote Sensing Image Generation (DIRSIG) tool is utilized to simulate on-orbit TIRS data. Appropriate sites on the Earth are identified and side-slither data is generated. The simulated on-orbit data is then compared to pre-launch calibration data to determine whether this calibration approach is viable to track the calibration of TIRS over its orbital lifetime.