On-orbit spatial characterizations for Terra MODIS

Abstract

MODerate Resolution Imaging Spectroradiometer (MODIS) Proto-Flight Model (PFM) on-orbit spatial characterization includes Band to Band registration (BBR) and the Modulation Transfer Function (MTF) of 36 bands located on four focal plane assemblies (VIS, NIR, SMWIR, and LWIR). These parameters were also measured prelaunch using ground calibration equipment. The on-board Spectro-Radiometric Calibration Assembly (SRCA) was used both prelaunch and on-orbit to monitor the BBR and MTF changes. In this paper, we report the MODIS on-orbit spatial characterization results derived from the SRCA and their comparisons with pre-launch values. Results from SRCA measurements show that the BBR stabilized on-orbit after about 100 days. Currently, the averaged FPA positions in the along-scan direction, relative to band 1 (NIR), have changed from prelaunch values by -2m for VIS, 17m for SMWIR, and -20m for LWIR; along-track changes are 43m for VIS, -36m for SMWIR, and -22m for LWIR. The MTF in the along-scan direction shows a small improvement over prelaunch. Also in this paper, we discuss a methodology that uses the sensor's on-orbit views of the Moon for the BBR characterization. Comparison of the results from the Moon and those from the SRCA provides an evaluation of the methodology and its applicability for other remote sensing instruments without an on-board spatial characterization calibrator.