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Improving the photometric precision of IRAC Channel 1

Mighell, Kenneth J. and Glaccum, William and Hoffmann, William (2008) Improving the photometric precision of IRAC Channel 1. In: Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter. Proceedings of SPIE. No.7010. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 70102W. ISBN 9780819472205.

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Planning is underway for a possible post-cryogenic mission with the Spitzer Space Telescope. Only Channels 1 and 2 (3.6 and 4.5 μm) of the Infrared Array Camera (IRAC) will be operational; they will have unmatched sensitivity from 3 to 5 microns until the James Webb Space Telescope is launched. At SPIE Orlando, Mighell described his NASA-funded MATPHOT algorithm for precision stellar photometry and astrometry and presented MATPHOT-based simulations that suggested Channel 1 stellar photometry may be significantly improved by modeling the nonuniform RQE within each pixel, which, when not taken into account in aperture photometry, causes the derived flux to vary according to where the centroid falls within a single pixel (the pixel-phase effect). We analyze archival observations of calibration stars and compare the precision of stellar aperture photometry, with the recommended 1-dimensional and a new 2-dimensional pixel-phase aperture-flux correction, and MATPHOT-based PSF-fitting photometry which accounts for the observed loss of stellar flux due to the nonuniform intrapixel quantum efficiency. We show how the precision of aperture photometry of bright isolated stars corrected with the new 2-dimensional aperture-flux correction function can yield photometry that is almost as precise as that produced by PSF-fitting procedures. This timely research effort is intended to enhance the science return not only of observations already in Spitzer data archive but also those that would be made during the Spitzer Warm Mission.

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Additional Information:© 2008 Society of Photo-Optical Instrumentation Engineers (SPIE). We wish to thank David Elliott, Patrick Lowrance, and the rest of the IRAC Instrument Team for their support of this research effort. I also wish to thank Mike Merrill and Ron Probst for many useful discussions about state-of-the-art near-infrared detectors. This work has been supported by a grant from the National Aeronautics and Space Administration (NASA), Interagency Order No. NNG06EC81I which was awarded by the Applied Information Systems Research (AISR) Program of NASA’s Science Mission Directorate. Additional support was provided by an award issued by JPL/Caltech (Spitzer Space Telescope Cycle 4 Archive Proposal #40106; Subcontract No. 1311641).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:stellar photometry, astrometry, infrared detectors, Spitzer Space Telescope, IRAC, MATPHOT
Series Name:Proceedings of SPIE
Issue or Number:7010
Record Number:CaltechAUTHORS:20190516-160301460
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Official Citation:Kenneth J. Mighell, William Glaccum, and William Hoffmann "Improving the photometric precision of IRAC Channel 1", Proc. SPIE 7010, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 70102W (12 July 2008); doi: 10.1117/12.789801;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95551
Deposited By: Tony Diaz
Deposited On:17 May 2019 04:01
Last Modified:16 Nov 2021 17:13

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