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Wu, A, Xiong, X, Cao, C (2008). Terra and Aqua MODIS inter-comparison of three reflective solar bands using AVHRR onboard the NOAA-KLM satellites. INTERNATIONAL JOURNAL OF REMOTE SENSING, 29(7), 1997-2010.

Cross-sensor inter-comparison is important to assess calibration quality and consistency and ensure continuity of observational datasets. This study conducts an inter-comparison of Terra and Aqua MODIS (the MODerate Resolution Imaging Spectroradiometer) to examine the overall calibration consistency of the reflective solar bands. Observations obtained from AVHRR (the Advanced Very High Resolution Radiometer) onboard the NOAA-KLM series of satellites are used as a transfer radiometer to examine three MODIS bands at 0.65 (visible), 0.85 (near-IR) and 1.64m (far near-IR) that match spectrally with AVHRR channels. Coincident events are sampled at a frequency of about once per month with each containing at least 3000pixel-by-pixel matched data points. Multiple AVHRR sensors on-board NOAA-15 to 18 satellites are used to check the repeatability of the Terra/Aqua MODIS inter-comparison results. The same approach applied in previous studies is used with defined criteria to generate coincident and co-located near nadir MODIS and AVHRR pixel pairs matched in footprint. Terra and Aqua MODIS to AVHRR reflectance ratios are derived from matched pixel pairs with the same AVHRR used as a transfer radiometer. The ratio differences between Terra and Aqua MODIS/AVHRR give an indication of the calibration biases between the two MODIS instruments. Effects due to pixel footprint mismatch, band spectral differences and surface and atmospheric bi-directional reflectance distributions (BRDFs) are discussed. Trending results from 2002 to 2006 show that Terra and Aqua MODIS reflectances agree with each other within 2% for the three reflective solar bands.



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