Design and Projected Performance of MODIS — A Moderate-Resolution Imaging Spectroradiometer for the Earth Observing System (EOS)
MODIS, a 36 band imaging spectroradiometer, is a key component of EOS, NASA’s 15-year mission to measure global climate change. MODIS is being developed by Hughes/Santa Barbara Research Center for an initial launch on the EOS AM-1 spacecraft in June 1998. Five subsequent launches are planned on the AM and PM series of EOS spacecraft in order to generate the required 15 years of global coverage. The MODIS design was completed in January 1994, and fabrication of an engineering model is underway with delivery scheduled for February 1995.
The basic requirements for MODIS include 36 spectral bands that range from 0.4 to 14.4 micrometers with bandwidths of 10–50 nanometers in the 20 reflective bands and 50–500 nanometers in the 16 emissive bands. Spatial resolutions of 250, 500, and 1,000 meters at nadir will be scanned across a +\-55 degree swath from a 705 kilometer sun-synchronous orbit to give near two-day global coverage. Requirements for SNR’s of several thousand near the equator and NEDT’s of < 0.05K at 300K together with dynamic ranges sufficient to enable ocean, land and atmosphere science algorithms result in a twelve bit system with a 24-hour average data rate of 6.1 megabits per second. The MODIS design is a crosstrack scanning radiometer that is 1.11 × 1.61 × 1.17 meters, weighs 234 kilograms and requires an average of 180 watts of power.
The MODIS design has several unique subsystems including a Spectral Radiometric Calibration Assembly (SRCA), a solar diffuser, a Solar Diffuser Stability Monitor (SDSM), and a blackbody calibration target which will allow inflight calibration and characterization of the sensor, thereby enabling the required accuracy of the planned geophysical data products.
KeywordsMODIS Design Solar Zenith Angle Reflective Band Open Mirror Earth Observe System
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