Infrared Observations Of the Eclipsed Moon from Space


	MSX was a Ballistic Missile Defense Organization satellite with multiple disciplinary experimental objectives. Mill et al.⁵ give an overview of the spacecraft, instruments and mission objectives.
	The MSX spacecraft measures about 1.5x1.5x5.1 meters with a mass of 2.7 tons and supports four sets of electro-optical sensors. It is somewhat modular in construction giving it the rather ungainly appearance. The primary mission instrument was an infrared sensor, designated SPIRIT III for historical reasons, mounted at the center of the spacecraft. Arrayed around SPIRIT III are the four ultraviolet-visible imaging telescopes (UVISI) and the five ultraviolet to far red hyperspectral imaging instruments. Off to the side is the 20 cm Space-Based Visible (SBV) surveillance telescope. All the electro-optical sensors are referenced to the optical reference plane at the front of the spacecraft and boresighted with the SPIRIT III telescope.
	MSX was launched on 24 April 1996 into a ~900 km polar orbit. The first phase or infrared portion of the mission terminated on 20 February 1997, when the radiometer focal plane temperatures reached 13K. For the year following cryogen loss, Phase 2 emphasized astronomy and atmospheric measurements with the ultraviolet-far red sensors.
	_______________
	⁵Mill, J.D., R.R. O’Neil, S. Price, G.J. Romick, O.M. Uy, E.M. Gaposchkin, G.C. Light, W.W. Moore Jr., T.L. Murdock and A.T. Stair Jr., “Midcourse Space Experiment: Introduction to the Spacecraft, Instruments and Scientific Objectives,” J. Spacecraft and Rockets, 31, 900-907, 1994.