The Multiband Imaging Photometer for Spitzer (MIPS) provides long wavelength capability for the mission, in imaging bands at 24, 70, and 160µm and measurements of spectral energy distributions between 52 and 100µm at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The Si:As BIB 24µm array has excellent photometric properties, and measurements with rms relative errors of 1% or better can be obtained. The two longer wavelength arrays use Ge:Ga detectors with poor photometric stability. However, the use of 1.) a scan mirror to modulate the signals rapidly on these arrays, 2.) a system of on-board stimulators used for a relative calibration approximately every two minutes, and 3.) specialized reduction software result in good photometry with these arrays also, with rms relative errors of less than 10%.

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.

The purposes of the Phase II alignment are to coalign mirror pairs fr the FOC and FOS channels and to set the compensation inechathsms of each clwmel to the optimum positions to allow the overall system performance to be determined and verified through use of the RAS/HOMS equipment without requiring adjustment of the mechanism compensators chiring testing. This alignment process is performed with the COSTAR instrument installed in the COSTAR Alignment System (CAS), using a well characterized interferometer system as the optical sirce. The interferometer uses a custom designed reference sphere with built-in spherical aberration to enable the highly aberrated two-mirror systems to be observed in dib1e-pass. lii the COSTAR Phase II alignment, the DOB axial mechanism and the Ml tilt mechanisms are first positioned to optimize the interferometric measurements in the primary, or preferred, channel of the FOC instrument The mechanisms are then held fixed and the interferometer input repositkned to provide input to the secondary, or ganged, channel. The M2 bezels are then ShimiTied and laterally repositioned fx optimum perftxinance. With the DOB position fixed, the interferonieter is moved to the FOS primary channel and the Ml axial and tilt positions are set. The interferometer is moved to the secoodaiy FOS channel and the M2 position is set through adjustm&it c the shim and lateral position. The interferometer is then finally moved to the GURS channel and the Ml axial and tilt positions are set At the conclusion of the Phase II alignment, the COSTAR instrument is fully aligned and ready for perkrmance verification in the RAS/HOMS.

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