28 August 1998 STIS on-orbit testing: limiting magnitudes, spectral sensitivity, thermal flexure, and MAMA time-tagging
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Abstract
The Space Telescope Imaging Spectrograph (STIS), installed into the Hubble Space Telescope (HST) during the second servicing mission (SSM) in February 1197, has undergone the required servicing mission orbital verification (SMOV). The overall sensitivity of STIS is summarized for direct imagery in the visible with the charge coupled device (CCD), the near UV multi-anode microchannel-array (NUV MAMA) and the far UV MAMA (FUV MAMA) detectors and likewise for the spectroscopic modes. The FUV MAMA has exceedingly low background. The NUV MAMA has a higher, temperature-dependent background due to window phosphorescence. The principle gains of the CCD over WFPCs for limiting imaging sensitivity are: high quantum efficiency, wide bandpass, low dark current and low readout-noise. The CCD, like the WFPC2 CCDs, must ge annealed periodically to heat the hot pixels generated by radiation hits. Throughput of all modes has been stable at the 1 percent level or better except for the far UV, where sensitivity is dropping slowly across the order, but more rapidly below the Lyman alpha, and beyond 150 nm. This loss in sensitivity may be due to contamination similar to that which affected the first generation HST instruments. The thermal environment for STIS is warmer than specified in the HST Interface Control Document with the result that the back end of the STIS optical bench is not under positive thermal control. Temperature swings occur due to the spacecraft solar orientation and also due to power cycling of the MAMA low voltage power supplies that are turned off during orbits that encounter the South Atlantic Anomaly. Some motion of spectral and direct image formats occurs on the detector that is correlatable with changing aft bulkhead temperature and changes in external heatloads. The MAMA detectors are capable of time-tagging photon events within 125 microsecond resolution. The Crab Pulsar was used as a time standard and demonstrates the desired performance.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Theodore R. Gull, Bruce E. Woodgate, Randy A. Kimble, Charles W. Bowers, Steven B. Kraemer, Mary Elizabeth Kaiser, Ralph C. Bohlin, Steve J. Hulbert, Richard A. Shaw, Keith Feggans, Don J. Lindler, Jennifer L. Sandoval, Robert S. Hill, Nicholas R. Collins, Thomas M. Brown, Jeff A. Valenti, "STIS on-orbit testing: limiting magnitudes, spectral sensitivity, thermal flexure, and MAMA time-tagging", Proc. SPIE 3356, Space Telescopes and Instruments V, (28 August 1998); doi: 10.1117/12.324443; https://doi.org/10.1117/12.324443
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