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Published June 2018 | Submitted
Journal Article Open

Laboratory Measurement of the Brighter-fatter Effect in an H2RG Infrared Detector


The "brighter-fatter" (BF) effect is a phenomenon—originally discovered in charge coupled devices—in which the size of the detector point-spread function (PSF) increases with brightness. We present, for the first time, laboratory measurements demonstrating the existence of the effect in a Hawaii-2RG HgCdTe near-infrared (NIR) detector. We use JPL's Precision Projector Laboratory, a facility for emulating astronomical observations with UV/VIS/NIR detectors, to project about 17,000 point sources onto the detector to stimulate the effect. After calibrating the detector for nonlinearity with flat-fields, we find evidence that charge is nonlinearly shifted from bright pixels to neighboring pixels during exposures of point sources, consistent with the existence of a BF-type effect. NASAs Wide Field Infrared Survey Telescope (WFIRST) will use similar detectors to measure weak gravitational lensing from the shapes of hundreds of million of galaxies in the NIR. The WFIRST PSF size must be calibrated to ≈0.1% to avoid biased inferences of dark matter and dark energy parameters; therefore further study and calibration of the BF effect in realistic images will be crucial.

Additional Information

© 2018. The Astronomical Society of the Pacific. Received 2017 December 15; accepted 2018 February 13; published 2018 April 25. We thank Chris Hirata, Jeff Kruk, Dave Content, Mike Seiffert, Warren Holmes, the WFIRST detector requirements working group, the Euclid detector working group, and Goddard's Detector Characterization Laboratory group for useful discussions. We thank Stefanie Wachter for useful discussions and feedback on the initial drafts of this document. We thank Warren Holmes and the Euclid detector working group for providing the H2RG detector used in this work. We acknowledge funding from the WFIRST and Euclid projects. A.A.P. is supported by the Jet Propulsion Laboratory. A.A.P. acknowledges support from the Italian Ministry of Foreign Affairs and International Cooperation, Directorate General for Country Promotion. C.S., J.R., and E.H. are being supported in part by the Jet Propulsion Laboratory. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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