The MODIS/ASTER airborne simulator (MASTER) - a new instrument for earth science studies

The MODIS/ASTER Airborne Simulator was developed for the Advanced Spaceborn e Thermal Emission and Reflection Radiometer (ASTER) and Moderate Resolutio n Imaging Spectroradiometer (MODIS) projects. ASTER and MODIS are both spac eborne imaging instruments on the Tel-ra platform launched in the fall of 1 999. Currently MASTER is flown on the Department of Energy (DOE) King Air B eachcraft B200 aircraft and the NASA DC-8. In older to validate the in-flig ht performance of the instrument, the Jet Propulsion Laboratory and the Uni versity of Arizona conducted a joint experiment in December 1998. The exper iment involved overflights of the MASTER instrument at two sites at three e levations (2000, 4000, and 6000 m). The two sites: Ivanpah Playa, Californi a, and Lake Mead, Nevada, were selected to validate the visible-shortwave i nfrared and thermal infrared (TIR) channels, respectively. At Ivanpah Playa , a spectrometer was used to determine the surface reflectance and a sun ph otometer used to obtain the optical depth. At Lake Mead contact and radiome tric surface lake temperatures were measured by buoy-mounted thermistors an d self-calibrating radiometers, respectively. Atmospheric profiles of tempe rature, pressure, and relative humidity were obtained by launching an atmos pheric sounding balloon. The measured surface radiances were then propagate d to the at-sensor radiance using radiative transfer models driven by the l ocal atmospheric data. There was excellent agreement between the predicted radiance at sensor and the measured radiance at sensor at all three altitud es. The percent difference between the channels not strongly affected by th e atmosphere in the visible-shortwave infrared was typically 1-5% and the p ercent difference between the TIR channels not strongly affected by the atm osphere was typically less than 0.5%. These results indicate the MASTER ins trument should provide a well-calibrated instrument for Earth Science Studi es. It should prove particularly valuable for those studies that leverage i nformation across the electromagnetic spectrum from the visible to the TIR. (C) 2001 Elsevier Science Inc. All rights reserved.