MSX DESIGN PARAMETERS DRIVEN BY TARGETS AND BACKGROUNDS MSX Design Parameters Driven by Targets and Backgrounds

he underlying requirements for demonstrating space-based surveillance, acquisition, tracking, and discrimination of ballistic reentry vehicles and penetration aids were followed in the design of the Midcourse Space Experiment (MSX) satellite and sensors. The primary sensor is the totally cryogenic Spatial Infrared Imaging Telescope III (SPIRIT III), supported by multiple co-aligned visible and ultraviolet sensors. SPIRIT III is cooled with solid hydrogen and has an expected minimal on-orbit life of 15 months. The 35-cm aperture and multiple focal planes with different spectral passbands were designed for long-range target capability and background measurements of the structure in the Earth-limb radiance. To detect and track reentry vehicles at ranges of 6000 km or more while viewing near Earth, a sensor must have an excellent off-axis reimaging optical system with a Lyot stop and superpolished primary and secondary mirrors. Superpolished cryogenic mirrors are extremely sensitive to contamination, so MSX also carries a unique suite of contamination monitoring sensors, particularly for on-orbit H2O and particles. MSX will be the first space experiment to correlate optical contamination (changes in nonrejected Earth radiance) with the satellite environment. T