Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21942509m&link_type=abstract
American Astronomical Society, AAS Meeting #219, #425.09
Astronomy and Astrophysics
Astrophysics
Scientific paper
The measured distance between two stars on a single Spitzer Space Telescope Infrared Array Camera (IRAC) Channel 1 (Ch1) BCD image can be systematically off by as much as one-fifth of a pixel which is 0.24 arcsec on the sky -- if standard intensity-weighted mean centroids are calculated (Mighell, Glaccum, & Hoffman 2008). The square centroid error distribution is well modeled by using a Point Spread Function (PSF) described by a diffraction-limited Airy pattern at 3.6 microns with a 60 percent circular central obscuration. This simple model describes (1) the separability of the centroid errors in the X and Y direction, (2) the size (amplitude) of the maximum centroid errors in X and Y, and (3) the shape (nearly sinusoidal) and (almost) the phase of the separable centroid errors as a function of X and Y pixel phase. The primary physical cause of the square centroid error distribution is that the space-based nearly-diffraction-limited PSF of the IRAC Ch1 PSF was strongly undersampled at the focal plane of the IRAC Ch1 camera by its detector array. This work has been supported by a grant from the National Aeronautics and Space Administration (NASA), NNX10AD45G, which was awarded by the Astrophysics Data Analysis Program (ADAP) of NASA's Science Mission Directorate.
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