Four-years on-orbit spectral characterization results for Aqua MODIS reflective solar bands

The Moderate Resolution Imaging Spectroradiometer (MODIS) flight model 1 (FM-1) was launched on-board NASA's EOS Aqua spacecraft on May 04, 2002. MODIS has 20 reflective solar bands (RSB) with wavelengths from 0.41 to 2.2 mu m and 16 thermal emissive bands (TEB) with wavelengths from 3.7 to 14.4 mu m. Typical sensor spectral characterization includes measurements of in-band (113) and out-of-band (OOB) relative spectral responses (RSR) or spectral response functions (SRF), center wavelengths (CW) and bandwidths (BW). During MODIS instrument prelaunch calibration and characterization, these parameters were measured using a spectral measurement assembly (SpMA) by the instrument vendor. In addition to its on-orbit radiometric calibration capability, MODIS has a unique on-board calibrator - spectro-radiometric calibration assembly (SRCA) that can be used to monitor RSB on-orbit spectral performance. This paper presents an over-view of MODIS spectral characterization methodologies, from pre-launch to on-orbit. It describes Aqua MODIS SRCA operational activities in spectral mode, summarizes the results from its four-years of on-orbit spectral measurements, and discusses lessons learned for future sensor design and development. The results show that on-orbit changes of Aqua MODIS RSB center wavelengths and bandwidths have been very small, typically less than 0.5nm for the CW and less than 1nm for the BW.