Intercomparison of multispectral imagers over natural targets

Aqua MODIS, AATSR, MERIS and POLDER-3 data are directly compared at top of the atmosphere level for nearly concomitant observation carried out under nearly identical or reciprocal geometries. Comparisons are carried out over the Salar de Uyuni in Bolivia and the Libyan desert. The results of the here presented simple methodology show that MERIS and A-MODIS are radiometrically in line. Intercomparison between MERIS and AATSR indicate that the radiometry of the instrument has significantly changed since late 2005: +0.5%/year (+/-2.9%/year) at 865 nm, -7.5%/year (+/-2.4%/year) at 670 nm and -9.4%/year (+/-1.5%/year) at 560 nm. The intercomparison of A-MODIS and POLDER-3 indicates a possible early degradation of the POLDER-3 sensitivity of -1.9%/year (+/-1.69%/year) and -0.47%/year (+/-1.3%/year) respectively at 560 nm and 865 nm.