Selection of the Infrared Detectors for Wide Field Camera 3 on the Hubble Space Telescope M. Robberto 1,# , M. Stiavelli 1 , S. Baggett 1 , B. Hilbert 1 , J. W. MacKenty 1 , R. A. Kimble 2 , R. J. Hill 2 , D. A. Cottingham 2 , G. Delo 2 , S. D. Johnson 2,% , W. Landsman 2 , E. M. Malumuth 2, & , E. Polidan 2, % , A. M. Russel 2 , A. Waczynski 2, % , Wassel, E., Y. Wen 2,& , A. Haas 3 , J. T. Montroy 3 , E. Piquette 3 , K. Vural 3 , C. Cabelli 3 , and D. N. B. Hall 4 1 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 2 NASA/Goddard Space Flight Center, Greenbelt, MD 20771 3 Rockwell Scientific Company, 5212 Verdugo Way, Camarillo, CA 93012 4 University of Hawaii, Institute for Astronomy, 640 N. Aohoku Place, Hilo, HI 96720 ABSTRACT Wide Field Camera 3 is a fourth generation instrument for the Hubble Space Telescope (HST), to be installed during the next HST Servicing Mission 4. For its infrared channel Rockwell Scientific Company has developed a new type of HgCdTe 1K×1K detector, called WFC3-1R, with cutoff wavelength at 1.7µm and 150K operating temperature. The WFC3-IR detectors are based on HgCdTe MBE grown on a CdZnTe substrate and use a new type of multiplexer, the Hawaii-1R MUX. Two flight detectors, a prime and a spare, have been recently selected on the basis of the measures performed at NASA Goddard Research Center – Detector Characterization Laboratory. These parts show quantum efficiency higher than 80% at λ=1.6µm and greater than 40% at λ>1.1µm, readout noise of ~25 e - rms with double correlated sampling, and mean dark current of ~0.04 e/s/pix at 150K. We show that the IR channel of WFC3, equipped with one of these flight detectors, beats the instrument requirements in all configurations and promises to have a discovery efficiency significantly higher than NICMOS. In particular, a two-band wide-area, deep survey made with WFC3 exceeds the discovery efficiency of NICMOS before and after the installation of NCS by a factor of 15 and 10, respectively. 1. INTRODUCTION WFC3 is the panchromatic fourth-generation instrument for HST, configured as a two-channel wide-field imager covering with diffraction limited performance the entire wavelength range between 2000Å and 1.72μm (Cheng et al. 2002; MacKenty et al 2002). It has an optical and an infrared channel, the latter spanning between 0.8μm and 1.72μm. With this range falls the minimum of background emission at the focal plane of the HST, due to the relatively high temperature (~300K, Robberto et al. 2000) of the optical assembly. An IR detector optimized for this spectral region can be operated at relatively high temperatures and still keep the dark current at an acceptably low level, due to the relatively large bandgap. Moreover, temperatures as low as ~150K can be achieved and maintained indefinitely by thermoelectric coolers, unlike disposable cryogenic fluids like LN 2 that allow short instrument lifetime. In July 2000, Rockwell Scientific Company, LLC (RSC) was contracted to fabricate the WFC3-1R FPA, a 1024x1024 hybrid HgCdTe device MBE grown on a CdZnTe substrate, with Hg-Cd stoichiometric balance tuned to provide a long- wavelength cutoff at ~1.7µm and a T=150K operating temperature. The detector array is indium bonded to the new # On Assignment from the Space Telescope Operations Division of the European Space Agency (ESA) % Global Science and Technology, Inc. & Science Systems and Applications, Inc.