Serendipitous background monitoring of the Hubble Space Telescope's Faint Object Spectrograph

John E. Fitch, Glenn Schneider

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The nature of the Hubble Space Telescope's (HST) low Earth orbit imposes scheduling restrictions and interruptions in the data collection periods for it's compliment of scientific instruments. During many of these times the Faint Object Spectrograph (FOS) is in a full operational configuration and is taking detector background measurements which are continually reported in HST's engineering telemetry stream. These data are primarily used to monitor the instrument for changes in behavior resulting, principally, from intermittently noisy diodes in its digicon arrays. These same data may be used to monitor temporal changes in the charged particle environment of HST's near-earth orbit. We present here the results of a study of two years of on-orbit FOS background data obtained serendipitously during periods while the FOS in an operational state, but not exposing on external, or calibration targets. These in situ data, which represent more than 100,000 discrete samples (equivalent to more than 1100 orbits) have allowed us to accurately measure variations in the background proton flux seen by the FOS. An analysis of these variations have permitted us to model the geomagnetic environment of the South Atlantic Anomaly (SAA) as a function of time as well as the change in detector background as a function of geomagnetic latitude.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsPierre Y. Bely, James B. Breckinridge
PublisherPubl by Society of Photo-Optical Instrumentation Engineers
Number of pages10
ISBN (Print)0819411817
StatePublished - 1993
Externally publishedYes
EventSpace Astronomical Telescopes and Instruments II - Orlando, FL, USA
Duration: Apr 13 1993Apr 14 1993

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


ConferenceSpace Astronomical Telescopes and Instruments II
CityOrlando, FL, USA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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