MODIS Correction Algorithm for Out-of-band Response in the Short-wave IR Bands

摘要

The MODerate Resolution Imaging Spectroradiometer (MODIS) has 36 spectral bands with wavelengths from 0.41 to 14.2 micrometers. The 36 spectral bands, a total of 490 detectors, are distributed on four focal plane assemblies (FPAs): visible (VIS), near infrared (NIR), short- and mid-wave infrared (SMIR), and long-wave infrared (LWIR). Nearly identical copies of MODIS are currently operating onboard the NASA EOS Terra spacecraft (launched on December 18, 1999) and Aqua spacecraft (launched on May 4, 2002), providing complementing global observations for the studies of the Earth system. Pre-launch and on-orbit characterizations of both Terra and Aqua MODIS instruments have shown small but non-negligible out-of-band (OOB) response in the sensors' short-wave infrared bands (SWIR: Bands 5-7 and 26). To minimize the impact due to OOB response on the MODIS SWIR bands calibration and the Earth scene retrieval, a correction algorithm has been developed and implemented in the Level 1B (L1B) software for both Terra and Aqua MODIS. In this paper, we describe this algorithm and its applications to the MODIS calibration. We will illustrate how the correction coefficients are derived from on-orbit observations and discuss the test procedures involved before algorithm implementation in the L1B code. Actual performance of this algorithm will be evaluated and compared for both Terra and Aqua MODIS.