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More Flexibility in Representing Geometric Distortion in Astronomical Images

Shupe, David L. and Laher, Russ R. and Storrie-Lombardi, Lisa and Surace, Jason and Grillmair, Carl J. and Levitan, David and Sesar, Branimir (2012) More Flexibility in Representing Geometric Distortion in Astronomical Images. In: Software and Cyberinfrastructure for Astronomy II. Proceedings of the SPIE. No.8451. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 84511M. ISBN 978-0-8194-9152-7.

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A number of popular software tools in the public domain are used by astronomers, professional and amateur alike, but some of the tools that have similar purposes cannot be easily interchanged, owing to the lack of a common standard. For the case of image distortion, SCAMP and SExtractor, available from, perform astrometric calibration and source-object extraction on image data, and image-data geometric distortion is computed in celestial coordinates with polynomial coefficients stored in the FITS header with the PV i_j keywords. Another widely-used astrometric-calibration service,, solves for distortion in pixel coordinates using the SIP convention that was introduced by the Spitzer Science Center. Up until now, due to the complexity of these distortion representations, it was very difficult to use the output of one of these packages as input to the other. New Python software, along with faster-computing C-language translations, have been developed at the Infrared Processing and Analysis Center (IPAC) to convert FITS-image headers from PV to SIP and vice versa. It is now possible to straightforwardly use for astrometric calibration and then SExtractor for source-object extraction. The new software also enables astrometric calibration by SCAMP followed by image visualization with tools that support SIP distortion, but not PV . The software has been incorporated into the image-processing pipelines of the Palomar Transient Factory (PTF), which generate FITS images with headers containing both distortion representations. The software permits the conversion of archived images, such as from the Spitzer Heritage Archive and NASA/IPAC Infrared Science Archive, from SIP to PV or vice versa. This new capability renders unnecessary any new representation, such as the proposed TPV distortion convention.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Shupe, David L.0000-0003-4401-0430
Laher, Russ R.0000-0003-2451-5482
Storrie-Lombardi, Lisa0000-0002-5987-5210
Surace, Jason0000-0001-7291-0087
Grillmair, Carl J.0000-0003-4072-169X
Sesar, Branimir0000-0002-0834-3978
Additional Information:© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). September 24, 2012. PTF is a scientific collaboration between the California Institute of Technology, Columbia University, Las Cumbres Observatory, the Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science. This interproject work was performed at the Spitzer Science Center and the NASA Herschel Science Center as part of missions/projects managed by Jet Propulsion Laboratory, California Institute of Technology, under contracts with the National Aeronautics and Space Administration.
Group:Space Radiation Laboratory, Infrared Processing and Analysis Center (IPAC)
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Series Name:Proceedings of the SPIE
Issue or Number:8451
Record Number:CaltechAUTHORS:20130206-153455094
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Official Citation:More flexibility in representing geometric distortion in astronomical images David L. Shupe, Russ R. Laher, Lisa Storrie-Lombardi, Jason Surace, Carl Grillmair, David Levitan, Branimir Sesar Proc. SPIE 8451, Software and Cyberinfrastructure for Astronomy II, 84511M (September 24, 2012); doi: 10.1117/12.925460
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36801
Deposited On:08 Feb 2013 17:27
Last Modified:09 Nov 2021 23:24

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