Hubble Space Telescope Call for Proposals for Cycle 31

STScI solicits proposals for HST Observing, Archival, and Theoretical Research. The full details are made available through two documents, the Call for Proposals, and the HST Primer. Downloadable PDF collections of these articles are provided as a courtesy, made available and updated when feasible. The online documentation is the authority, and will be updated with the latest information.

Late Breaking News

  • May 19, 2023:

    • There was a typo in the text regarding AR program guidelines. Please note, any HST data that you wish to analyze must reside (or be expected to reside) in the Archive, and be released from exclusive access rights by the start of Cycle 31 (December 1, 2023). This restriction does not apply to the ULLYSES datasets.
  • May 8, 2023:

    • There will be one Mid-Cycle opportunity in Cycle 31. The deadline for Mid-Cycle submissions will be Wednesday November 15, 2023 at 11:59pm. Notification of results are expected in mid-January 2024.
  • May 2, 2023:

    • Proposers submitting combined GO-Archival proposals should use the GO template, and include the Analysis Plan section.
  • May 1, 2023:

    • The ACS/SBC offers far-UV imaging with a low dark rate that historically varies from ~1E-5 to ~5E-5 cts/sec/pix during the course of a visit, as the detector temperature increases by ~10 degrees C for a visit spanning 5 orbits.  Recently, the dark rate has been elevated by a factor of ~2, even though the temperature profile has not changed.  This behavior is under investigation, but users considering the SBC for their observations should plan on shorter visits (1-2 orbits) to help mitigate this behavior, if it persists.

See also HST New and Important Features.


We invite scientists to participate in Cycle 31 of the Hubble Space Telescope (HST). The telescope and its instruments were built under the auspices of the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). Management of HST’s scientific program is carried out by the Space Telescope Science Institute (STScI). We anticipate allocating up to 2300 orbits in this cycle, including 1200 orbits for Small Programs, 600 orbits for Medium Programs, and 500 for Large and Treasury Programs. An additional 850 Snapshot observations and 500 Pure-Parallel observations may be allocated. Abstracts of previously accepted programs can be found on the HST proposal catalogs webpage.

This document establishes the goals, requirements, and policies for General Observer (GO) and Archival Research (AR) programs in Cycle 31. The table of contents for the web version of this document is on the right side of the page, and links there can take you to any page from any other page (click the arrow to expand the entire table of contents under "Hubble Space Telescope Call for Proposals for Cycle 31"). The links at the top of each page correspond to sections within that given page.

Proposing Calendar and Deadlines

Cycle 31 Dates: December 1, 2023 – September 30, 2024

Cycle 31 Phase I proposal deadline: Wednesday May 24, 2023 at 8:00pm EDT

Cycle 31 Peer Review meeting: August 1-9, 2023

Cycle 31 Phase II proposal deadline: September 15, 2023

Cycle 31 Budget submission deadline: September 28, 2023 at 5:00pm EDT

Cycle 31 Mid-Cycle deadline: Wednesday November 15, 2023 at 11:59pm EST

Notification of the outcome of the Phase I selection process will be sent to all proposers in late August 2023.

What's New for Cycle 31

See HST New and Important Features

Where to Get Help

Who's Responsible

The HST Call for Proposals and related materials for Cycle 31 were edited by Laura Watkins and Molly Peeples. The Associate Director for Science, Neill Reid, and the Science Mission Office (SMO) at STScI are responsible for the oversight of the HST science program selection process. SMO members include Alessandra Aloisi (SMO Mission Head), Elena Sabbi (SMO Deputy Mission Head), Laura Watkins (SMO Deputy Mission Head), Claus Leitherer (Hubble Science Policies Lead), Molly Peeples (Hubble Science Policies Deputy Lead), Katey Alatalo, Christine Chen, Andrew Fruchter, Amaya Moro-Martin, Jamila Pegues, Linda Smith, and Technical Manager Brett Blacker.

Download the PDF

This PDF is provided as a courtesy, made available and updated when feasible. The online documentation is the authority, and will be updated with the latest information.

Next: HST New and Important Features