The Advanced Camera for Surveys is an instrument containing two CCD cameras and a MAMA detector being built by Ball Aerospace and Technologies Corporation for NASA. The instrument will be placed aboard the Hubble Space Telescope during a space shuttle mission in December 1999. The CCD detectors need to operate at a temperature below -80*C in order to avoid unacceptable dark current and signal noise. This cooling is achieved through detailed thermal design which minimizes the parasitic load to a 4K x 4K array and cools the detector with a combination of thermo-electric coolers (TECs). This paper will describe the innovative thermal design necessary to maintain the CCD at its cold operating temperature while providing the means to reject the heat generated by the TECs. It will focus on optimization techniques to manage parasitic loads including material selection, surface finishes, and thermal isolation. The paper will also address analytical techniques to characterize TEC performance. Finally, a comparison with the STIS CCD design currently operating in the Hubble Space Telescope will be made.
Keywords: HST Advanced Camera, CCDs, thermal design, TECs
Mr. Greg Johnson received a Bachelor of Science in Engineering from the United States Military Academy in 1968 and a Master of Science in Physics from the University of Colorado in 1974. After a three-year assignment as Assistant Professor in the Department of Physics at West Point, Johnson joined Ball Aerospace in 1980. Since then he has worked in the Thermal Group on a wide variety of programs, from spacecraft to instruments and from cryogenic applications to laser-hardening phenomena.
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