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Proceedings Paper

NIRCAM image simulations for NGST wavefront sensing
Author(s): Anand Sivaramakrishnan; Russell B. Makidon; Donald Frank Figer; Robert Ian Jedrzejewski; Howard A. Bushouse; John E. Krist; H.S. Peter Stockman; Philip Hodge; Nadezhda M. Dencheva; Bernard J. Rauscher; Victoria G. Laidler; Catherine Mayumi Ohara; David C. Redding; Myungshin Im; Joel D. Offenberg
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Paper Abstract

The Next Generation Space Telescope (NGST) will be a segmented, deployable, infrared-optimized 6.5m space telescope. Its active primary segments will be aligned, co-phased, and then fine-tuned in order to deliver image quality sufficient for the telescope's intended scientific goals. Wavefront sensing used to drive this tuning will come from the analysis of focussed and defocussed images taken with its near-IR science camera, NIRCAM. There is a pressing need to verify that this will be possible with the near-IR detectors that are still under development for NGST. We create simulated NIRCAM images to test the maintenance phase of this plan. Our simulations incorporate Poisson and electronics read noise, and are designed to be able to include various detector and electronics non-linearities. We present our first such simulation, using known or predicted properties of HAWAII HgCdTe focal plane array detectors. Detector effects characterized by the Independent Detector Testing Laboratory will be included as they become available. Simulating InSb detectors can also be done within this framework in future. We generate Point-Spread Functions (PSF's) for a segmented aperture geometry with various wavefront aberrations, and convolve this with typical galaxy backgrounds and stellar foregrounds. We then simulate up-the-ramp (MULTIACCUM in HST parlance) exposures with cosmic ray hits. We pass these images through the HST NICMOS `CALNICA' calibration task to filter out cosmic ray hits. The final images are to be fed to wavefront sensing software, in order to find the ranges of exposure times, filter bandpass, defocus, and calibration star magnitude required to keep the NGST image within its specifications.

Paper Details

Date Published: 5 March 2003
PDF: 10 pages
Proc. SPIE 4850, IR Space Telescopes and Instruments, (5 March 2003); doi: 10.1117/12.461933
Show Author Affiliations
Anand Sivaramakrishnan, Space Telescope Science Institute (United States)
Russell B. Makidon, Space Telescope Science Institute (United States)
Donald Frank Figer, Space Telescope Science Institute (United States)
Robert Ian Jedrzejewski, Space Telescope Science Institute (United States)
Howard A. Bushouse, Space Telescope Science Institute (United States)
John E. Krist, Space Telescope Science Institute (United States)
H.S. Peter Stockman, Space Telescope Science Institute (United States)
Philip Hodge, Space Telescope Science Institute (United States)
Nadezhda M. Dencheva, Space Telescope Science Institute (United States)
Bernard J. Rauscher, Space Telescope Science Institute (United States)
Victoria G. Laidler, Space Telescope Science Institute (United States)
Computer Sciences Corp. (United States)
Catherine Mayumi Ohara, Jet Propulsion Lab. (United States)
David C. Redding, Jet Propulsion Lab. (United States)
Myungshin Im, California Institute of Technology (United States)
Joel D. Offenberg, Science Systems and Applications, Inc. (United States)

Published in SPIE Proceedings Vol. 4850:
IR Space Telescopes and Instruments
John C. Mather, Editor(s)

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