Irradiance-based cross-calibration of Landsat-5 and Landsat-7 thematic mapper sensors

On 2 June 1999 Landsat-5 and Landsat-7 passed over north-central Nebraska collecting Thematic Mapper (TM) data for essentially the same spatial location, with an acquisition time differing by less than 20 min. At the Niobrara Nature Preserve, Nebraska site, two multifilter rotating shadowband radiometers (MFRSRs), a Cimel sunphotometer, a Microtops sunphotometer, and an ASD-FR spectroradiometer were used to take ground-based readings. This dataset offered a unique opportunity to absolutely calibrate both instruments, and also to cross-calibrate TM with Enhanced Thematic Mapper Plus (ETM +) the new thematic mapper aboard Landsat-7. ModTran3 radiative transfer code, based on the Nebraska datasets, was calibrated to match observed atmospheric transmittance and diffuse-to-global ratios, employing ground reflectance values, for each individual overpass. Having replicated those conditions, models were then extrapolated to satellite orbits, and exoatmospheric irradiances calculated. Finally, by obtaining actual imagery from each satellite, a cross-calibration comparison of the two satellites' TM sensor's responses was made.