Muttiband imaging photometer for SIRTF

The Multiband Imaging Photometer for SIRTF (MIPS) provides the Space Infrared Telescope Facility (SIRTF) with imaging, photometry, and total power measurement capability in broad spectral bands centered at 24, 70, and 160tm, and with low resolution spectroscopy between 50 and 95p.m. The optical train directs the light from three zones in the telescope focal plane to three detector arrays: l28x128 Si:As BIB, 32x32 Ge:Ga, and 2x20 stressed Ge:Ga. A single axis scan mirror is placed at a pupil to allow rapid motion of the field of view as required to modulate above the 1/f noise in the germanium detectors. The scan mirror also directs the light into the different optical paths of the instrument and makes possible an efficient mapping mode in which the telescope line of sight is scanned continuously while the scan mirror freezes the image motion on the detector arrays. The instrument is designed with pixel sizes that oversample the telescope Airy pattern to operate at the diffraction limit and, through image processing, to allow superresolution beyond the traditional Rayleigh criterion. The instrument performance and interface requirements, the design concept, and the mechanical, optical, thermal, electrical, software, and radiometric aspects of MIPS are discussed in this paper. Solutions are shown to the challenge of operating the instrument below 3K, with focal plane cooling requirements down to 1.5K. The optical concept allows the versatile operations described above with only a single mechanism and includes extensive self-test and on-board calibration capabilities. In addition, we discuss the approach to cryogenic end-to-end testing and calibration prior to delivery of the instrument for integration into SIRTF.