On-orbit performance of the Spitzer Space Telescope

Roellig, Thomas L.; Werner, M. W.; Gallagher, David; Irace, William R.; Fazio, G. G.; Houck, J. R.; Rieke, G. H.; Wilson, Robyn; Soifer, T.

doi:10.1117/12.551037

Cited by 10 publications

(4 citation statements)

References 11 publications

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“…Then by Fast Fourier Transform, compute the diffraction image distribution at the plane of the array for each wavelength sampled. 3. Sum these intensity distributions over wavelength, weighting for the spectral response of the array and filter and for the source spectrum (Rayleigh-Jeans for a star).…”

Section: Introductionmentioning

confidence: 99%

Determination of Spitzer Space Telescope focus from IRAC images without a focus slew

et al. 2004

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Prior to launch, the Spitzer Space Telescope (SST) secondary focus mechanism was set to a predicted desired in-orbit focus value. This predicted setting, determined from double-pass cold chamber measurements and calculated groundto-orbit corrections, had an uncertainty greater than the required in-orbit focus accuracy. Because of concern about the potential for failure in a cryogenic mechanism affecting all Spitzer instruments, it was required that any focus correction be made in a set of moves directly from the initial to the desired setting. The task of determining the required focus moves fell to IRAC (Infrared Array Camera), the instrument most affected by and sensitive to defocus. To determine the focus directly from examining images at a fixed focus, we developed two methods, "Simfit" and "Focus Diversity" (W. F. Hoffmann, et. al. 1 ). Simfit finds the focus by obtaining the best match between observed images and families of simulated images at a range of focus settings. Focus Diversity utilizes the focal plane curvature to find the best fit of the varied image blur over the focal plane to a model defocus curve. Observations of a single star at many field locations in each of the four IRAC bands were analyzed before and during the refocus activity. The resulting refocus moves brought the focus close to the specified requirement of within 0.3 mm from the desired IRAC optimum focus. This is less than a "Diffraction Focus Unit" (λ×(f/ 2 )) of 0.52 mm at the SST focus at the shortest IRAC band (3.58 microns). The improvement in focus is apparent in both the appearance and the calculated noise-pixels of star images.

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Section: Introductionmentioning

confidence: 99%

Determination of Spitzer Space Telescope focus from IRAC images without a focus slew

et al. 2004

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“…The Infrared Array Camera (IRAC) 1,2,3,4 is one of three focal plane instruments in the Spitzer Space Telescope 5,6 . IRAC is a four-channel camera that obtains simultaneous images at 3.6, 4.5, 5.8, and 8 µm.…”

Section: Introductionmentioning

confidence: 99%

Normal and unusual transient events in IRAC images

et al. 2004

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The Spitzer Space Telescope Infrared Array Camera (IRAC) is a four-channel camera that uses two pairs of 256 x 256 pixel InSb and Si:As IBC detectors to provide simultaneous images at 3.6, 4.5, 5.8, and 8 µm. IRAC experiences a flux of cosmic rays that produce transient events in images from each of the arrays, with 5-7 pixels per second being affected in an IRAC integration. The vast majority of these transient events can be adequately characterized so they can be effectively detected and flagged by a pipeline software module. However, because of the nature of the arrays and their arrangement in the camera structure, a small fraction of the cosmic ray hits on IRAC produce transients with unusual morphologies that cannot be characterized in a general way. We present nominal cosmic ray rates observed for IRAC on-orbit and rates observed during a period of elevated solar proton flux following a series of X-class solar flares in late 2003. We also present a guide for observers to help identify unusual transient events in their data. We comment on the physical nature of the production of many of these unusual transients and how this mechanism differs from the production of "normal" transient events.

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“…The IRAC instrument 1,2 is a four-channel camera on board the Spitzer Space Telescope 3,4 that can obtain simultaneous 5.2×5.2 arcmin images in broad-band filters centered at wavelengths of 3.6, 4.5, 5.8, and 8 µm. Two nearly adjacent fields of view are imaged in pairs (3.6 and 5.8 µm; 4.5 and 8.0 µm) using dichroic beamsplitters.…”

Section: Introductionmentioning

confidence: 99%