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STScI will be performing network upgrades on the following dates:
  • Sat 17 Apr 2021, 7:00 AM - 2:00 PM EDT (11:00 - 18:00 UTC)
  • Sat 24 Apr 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sat 1 May 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sun 2 May 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sat 8 May 2021, TBD
  • Sun 9 May 2021, TBD
Services may be unavailable or interrupted during these times.

HST Data Reduction & Analysis

Hubble Space Telescope (HST) science data are stored in the HST Archive in FITS format. Information on the FITS header keywords in HST data files can be obtained from the keyword dictionary. Access to the archive is open to everybody but non-astronomers should be aware of the fact that HST data are intended for professional astronomical data reduction and analysis systems.

The Space Telescope Science Institute (STScI) supports dedicated software, the Space Telescope Science Analysis System (STSDAS), for reducing and analyzing HST data. This software works within the Image Reduction and Analysis Facility (IRAF).

Specific details about the format and content of science datasets can be found in the HST Data Handbook. For any questions about HST data reduction and analysis users should contact the STScI Help Desk at

Improved calibration of FOS data using new STSDAS software is available from the web site, along additional FOS-related news, documentation, and activities.

The HST proposal process involves various steps, going from the Call for Proposals, to writing and submitting a proposal (Phase I), to providing the details (Phase II). For more details please check this page.

The results of investigations with HST archive data are generally published in the scientific literature. All publications based on these data should carry an acknowledgment.