Radiometric cross-calibration of the Landsat-7 ETM+ and Landsat-5 TM sensors based on tandem data sets

Early in its mission, the Landsat-7 spacecraft was temporarily placed in a "tandem" orbit very close to that of the Landsat-5 spacecraft in order to f acilitate the establishment of sensor calibration continuity between the La ndsat-7 Enhanced Thematic Mapper Plus (ETM+) and Landsat-5 Thematic Mapper (TM) sensors. The key period for the tandem configuration was June 1-4, 199 9, during which hundreds of nearly coincident matching scenes were recorded by both the Landsat-7 ETM+ and, in cooperation with Space Imaging/EOSAT an d international ground stations, the Landsat-5 TM as well. The paper presen ts a methodology for radiometric cross-calibration of the solar reflective spectral bands of the Landsat-7 ETM+ and Landsat-5 TM sensors and results b ased on analysis of two different tandem image pairs for which ground refer ence data are available. With the well-calibrated ETM+ as a reference, the tandem-based cross-calibrations for the two image pairs yield TM responsivi ties that are consistent to each other to within 2% or better depending on the spectral band. Comparisons with independent methods and results obtaine d by other groups indicate that the tandem-based cross-calibration is withi n 3% of the independent results on average in spectral bands 1-4 but compar es less favorably in bands 5 and 7. The present study indicates that the ta ndem cross-calibration approach can provide a valuable "contemporary" calib ration update for Landsat-5 TM in the visible and near-infrared spectral ba nds based on the excellent radiometric performance of Landsat-7 ETM+. The m ethodology also incorporates adjustments for spectral band differences betw een the two Landsat sensors. Spectral band difference effects are shown to be more dependent on the surface reflectance spectrum than on atmospheric a nd illumination conditions. A variety of terrestrial surfaces are assessed regarding their suitability for Landsat radiometric cross-calibration in th e absence of surface reflectance spectra. Crown Copyright (C) 2001 Elsevier Inc. All rights reserved.