Inter-comparison of Aqua and Terra MODIS using Adeos-II GLI orbital intersections

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS), a key instrument for the NASA EOS mission, is currently operating on-board the Terra and Aqua spacecrafts. MODIS has 36 bands covering a spectral range from 0.41 to 14.4μm. It is a cross track scanning radiometer which samples over scan angles from -55° to +55° resulting a 2330km cross track by 10km along track swath each scan. The nadir spatial resolutions are 250m (2 bands), 500m (5 bands) and 1000m (29 bands). This study uses observations from simultaneous nadir overpasses (SNO) to conduct an inter-comparison of the Aqua and Terra MODIS. The GLobal Imager (GLI) onboard the Advanced Earth Observing Satellite-II (ADEOS_II, launched December 14, 2002) is used as a transfer reference since it has many bands which are spectrally similar to MODIS bands. The inter-comparison was performed on one visible band at 0.41μm, one near-IR band at 0.86μm, and six bands from the middle to longwave infrared between 3.7 and 12.3μm over a period from April to October 2003 when the GLI was operating normally. The results show that the Aqua and Terra MODIS agree to within 2% in radiance in the visible and near-IR bands. For the thermal bands, the differences in brightness temperature are less than 0.35K in the atmospheric window region between 11 and 12μm. Higher uncertainties in the other thermal bands are likely due to spectral differences between MODIS and GLI.