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Lossy Compression of Weak-Lensing Data

Vanderveld, R. Ali and Bernstein, Gary M. and Stoughton, Chris and Rhodes, Jason and Massey, Richard and Johnston, David and Dobke, Benjamin M. (2011) Lossy Compression of Weak-Lensing Data. Publications of the Astronomical Society of the Pacific, 123 (906). pp. 996-1003. ISSN 0004-6280.

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Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is, by construction, less than the Poisson error from photon shot noise. For simulated space-based images (without cosmic rays) digitized to the typical 16 bits pixel^(-1), application of the lossy compression followed by imagewise lossless compression yields images with only 2.4 bits pixel^(-1), a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies’ measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m ≈ -4 × 10^(-4). This bias is small when compared with the many other issues that precision weak-lensing surveys must confront; furthermore, we expect it to be reduced further with better calibration of ellipticity measurement methods.

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Additional Information:© 2011 Astronomical Society of the Pacific. Received 2011 April 29; accepted 2011 June 26; published 2011 July 12. This work was supported in part by the Kavli Institute for Cosmological Physics at the University of Chicago through grants NSF PHY-0114422 and NSF PHY-0551142 and an endowment from the Kavli Foundation and its founder Fred Kavli. This work was also carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, and funded by JPL’s Research and Technology Development Funds. C. S. and D. J. acknowledge support from the Fermi Research Alliance, LLC, under contract DE-AC02-07CH11359 with the US Department of Energy (DOE). G. M. B. acknowledges support from grant AST-0607667 from the National Science Foundation and DOE grant DE-FG02-95ER40893. R. M. acknowledges support from a Science and Technology Facilities Council Advanced Fellowship and from European Research Council grant MIRG-CT-208994.
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Kavli FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC02- 07CH11359
Science and Technology Facilities Council (STFC)UNSPECIFIED
European Research CouncilMIRG-CT-208994
Subject Keywords:Data Analysis and Techniques
Issue or Number:906
Record Number:CaltechAUTHORS:20110914-112416274
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Official Citation:Lossy Compression of Weak-Lensing Data R. Ali Vanderveld, Gary M. Bernstein, Chris Stoughton, Jason Rhodes, Richard Massey, David Johnston and Benjamin M. Dobke Publications of the Astronomical Society of the Pacific Vol. 123, No. 906 (August 2011), pp. 996-1003
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:25340
Deposited By: Jason Perez
Deposited On:20 Sep 2011 17:06
Last Modified:03 Oct 2019 03:05

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