Point source fitting of IRAC images using a PRF

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The IRAC PRFs

PRFs for IRAC have been created by Bill Hoffmann of the University of Arizona, a member of the IRAC instrument team. The starting point for these PRFs (070131 version) were the Code V optical models for Spitzer/IRAC made at the Goddard Space Flight Center. These were constructed on a 5x5 grid covering each of the IRAC arrays. Observations of a calibration star made during in-orbit checkout at each of these 25 positions per array were then deconvolved by their respective optical models. The results were averaged into a single convolution kernel per array which represents additional PRF scatter from unmodeled optical effects and spacecraft jitter. The intrapixel sensitivity function was estimated using a polynomial fit as a function of pixel phase. The PRFs were then transposed, and flipped in x and y to align them with the BCD coordinate system.