Improved calibration of Landsat-5 TM applicable for high-latitude and dark areas

Abstract

The Landsat-5 Thematic Mapper (TM) has provided data for more than 17 years, making it one of the most successful missions so far. TM sensor degradation is well documented and although efforts are made to account for this degradation when calibrating the sensor, such calibrations are often done over high reflective and bright surfaces in combination with a high solar irradiance. These conditions are not found in high-latitude and dark areas, making the calibration coefficients inappropriate to use. In this study reflectances obtained from TM bands 1-4 over a high-arctic area from 1987-1998 are compared to reflectances obtained from the Landsat-7 Enhanced Thematic Mapper Plus (ETMz) over the same area in 1999-2000. From the reflectance comparison it was found that a correction of the calibration gain could be described by a power function using days since launch as the controlling variable. From the power function, updated and lifetime calibration coefficients for TM bands 1-4 applicable for high-latitude and dark areas were determined. Furthermore, the study showed a continuous decrease of the TM sensor response with band 1 being the most affected and band 4 the most stable. The study also showed the possibility of using ETMz to determine updated calibration coefficients for TM by a cross-calibration even though the ETMz and TM scenes are not coincident.