Landsat sensor cross-calibration using nearly coincidental matching scenes

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 facilitate the establishment of sensor calibration continuity between the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) and Landsat-5 Thematic Mapper (TM) sensors. The key period for the tandem configuration was June 1-4, 1999, during which hundreds of nearly-coincident matching scenes were recorded by both the Landsat-7 ETM+ and, in cooperation with Space Imaging and international ground stations, the Landsat-5 TM as well. The paper presents a methodology for Landsat-7 ETM+ and Landsat-5 TM cross-calibration and results based on analysis of three tandem image pairs. The approach incorporates adjustments for spectral band differences between the two sensors. With the well- calibrated ETM+ as a reference, the tandem-based cross-calibrations for the three image pairs yield TM responsivities that are consistent to each other to within a few percent or better depending on the spectral band. Comparisons with independent methods and results obtained by other groups indicate that the tandem-based cross-calibration is in close agreement with the independent results in spectral bands 1-3 but compares less favourably in the other bands.