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R.A. Kimble (NASA's GSFC), J.W. MacKenty (STScI), R.J. Hill (NASA's GSFC), M. Robberto (STScI), G. Delo, R. Foltz, E.M. Malumuth, S. Reed, A.M. Russell, A. Waczynski, Y. Wen (NASA's GSFC), D. Figer (STScI), WFC3 Team
Wide Field Camera 3 is a powerful UV/visible/near-IR imager currently in development for installation into the Hubble Space Telescope. The IR channel of the instrument covers the wavelength range from 800 to 1700nm and will provide HST with a powerful capability for studying high-redshift galaxies, high-redshift Type Ia supernova “standard candles”, star formation regions, and planetary atmospheres. At the heart of the IR channel is a custom HgCdTe focal plane array (1024 x 1024 pixels) developed by Rockwell Science Center. A high-quality array has been packaged for flight and has demonstrated good performance in thermal-vacuum test. However, as described in the accompanying poster by Hill et al., we have discovered a radiation-induced luminescence phenomenon in the CdZnTe substrates on which the HgCdTe detection layers are grown; in the orbital radiation environment, the resulting background could potentially be strong enough to affect the sensitivity of WFC3 observations.
Fortunately, Rockwell is now capable of manufacturing high-quality HgCdTe arrays with the offending substrate removed. Hence, the WFC3 program is currently procuring new substrate-removed arrays to eliminate the radiation-induced background risk. Testing of the new arrays demonstrates that they exhibit greatly improved quantum efficiency performance vs. the original flight device. We report here on the performance of the new IR arrays in development for WFC3, present the sensitivity improvement that can be anticipated for the instrument, and describe the processing flow for getting a new flight array packaged and integrated for launch.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.