The Space Dynamics Laboratory at Utah State University built an infrared imaging radiometer with dual, large-format detector arrays and a passively cooled telescope for low earth orbit. The confocal detector arrays include a 128 X 128 HgCdTe array operating from 4.5 to 7.5 micrometers and a 256 X 256 InSb array operating from 2.0 to 4.5 micrometers . These arrays yield simultaneous dual-band images. A 13 cm aperture, passively cooled telescope with single- axis scan mirror gives high system sensitivity, excellent image quality, and precision tracking of targets and backgrounds without the usual complexity of cooled optics. High speed cryogenic filter wheels with 6 to 8 filters per detector provide for rapid band selection. A modular cooling system allows the detector arrays and filters to be cooled using either a mechanical cryocooler or a solid cryogen cryostat depending on mission requirements. An on-board calibration source performs pixel-to-pixel uniformity correction on- orbit.