Hubble Space Telescope Call for Proposals for Cycle 33
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
- April 13, 2025:
- We will acknowledge receipt of proposals within 5 business days of the deadline.
- April 4, 2025:
- Shared Risk for ACS/WFC and WFC3/UVIS: As announced in HST New and Important Features, ACS/WFC and WFC3/IR are offered at shared risk in Cycle 33. A decision on their status will be made when the outcome of the senior review and subsequent budgetary direction from NASA HQ are known. If NASA does not allocate funding to continue fully supporting ACS/WFC and WFC3/IR, we anticipate that:
- Only basic calibration activities (anneals, superdark, and superbias updates for ACS/WFC; bad pixel updates for WFC3/IR) would be performed. The calibration accuracy would drift at a rate of a few tenths of a mmag per year.
- There would be no user support, meaning no contact scientist, no helpdesk, no documentation updates etc.
- HOPRs would not be allowed as there would be no staff to assess the quality of data in case of suspected observation failure.
- The use of ACS/WFC or WFC3/IR will not be penalized during proposal selection. However, in cases where the science can be equivalently achieved with WFC3/UVIS (for ACS/WFC) or JWST (for WFC3/IR), users are encouraged to use these modes. In cases where the science cannot be achieved with WFC3/UVIS or JWST, users should therefore briefly justify why the use of WFC3/UVIS or JWST is not possible and ACS/WFC or WFC3/IR is required.
- Shared Risk for ACS/WFC and WFC3/UVIS: As announced in HST New and Important Features, ACS/WFC and WFC3/IR are offered at shared risk in Cycle 33. A decision on their status will be made when the outcome of the senior review and subsequent budgetary direction from NASA HQ are known. If NASA does not allocate funding to continue fully supporting ACS/WFC and WFC3/IR, we anticipate that:
- April 1, 2025:
- Observations of Moving Targets: We have relaxed the restrictions on observations of moving targets. Visits will have a typical practical limit of about 6 contiguous orbits, but are no longer strictly limited to 2 contiguous orbits.
- Observations of Moving Targets: We have relaxed the restrictions on observations of moving targets. Visits will have a typical practical limit of about 6 contiguous orbits, but are no longer strictly limited to 2 contiguous orbits.
- March 25, 2025:
- New COS Lifetime Usage Policy: Starting in Cycle 33, COS FUV programs will be limited to a maximum of 2% lifetime usage per Lifetime Position (LP), with usage beyond 1% requiring justification in the Phase I proposal. Proposers should consult the updated lifetime usage table to determine whether their proposed observations approach or exceed the usage limits.
- New COS Lifetime Usage Policy: Starting in Cycle 33, COS FUV programs will be limited to a maximum of 2% lifetime usage per Lifetime Position (LP), with usage beyond 1% requiring justification in the Phase I proposal. Proposers should consult the updated lifetime usage table to determine whether their proposed observations approach or exceed the usage limits.
- February 3, 2025:
- New COS Lifetime Positions: Starting in Cycle 33, FUV gratings G130M utilizing cenwaves 1055, 1096, 1222, and 1291 and G160M utilizing all cenwaves will move to use new lifetime positions (LPs). Similar to previous moves, these LPs have different overheads and spectral resolution. More information is available in the March 2025 STAN.
- New COS Lifetime Positions: Starting in Cycle 33, FUV gratings G130M utilizing cenwaves 1055, 1096, 1222, and 1291 and G160M utilizing all cenwaves will move to use new lifetime positions (LPs). Similar to previous moves, these LPs have different overheads and spectral resolution. More information is available in the March 2025 STAN.
- January 9, 2025:
- APT: APT 2024.7.1 is now available. Cycle 33 proposers should use this version to submit their proposals. Submissions started in earlier versions can be transferred to 2024.7.1.
See also HST New and Important Features.
Welcome
We invite scientists to participate in Cycle 33 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 2600 orbits in this cycle, including approximately 1300 orbits for Very Small and Small Programs, 650 orbits for Medium Programs, and 650 for Large and Treasury Programs. An additional 1000 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 33. 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 33"). The links at the top of each page correspond to sections within that given page.
Proposing Calendar and Deadlines
Cycle 33 Dates: November 1, 2025 - October 31, 2026
Cycle 33 Phase I proposal deadline: Thursday, April 10, 2025 at 8:00pm EDT
Cycle 33 Peer Review meeting: June 23 - July 3, 2025
Cycle 33 Phase II proposal deadline: anticipated August 14, 2025 at 5:00pm EDT
Cycle 33 Budget submission deadline: August 14, 2025 at 5:00pm EDT
Notification of the outcome of the Phase I selection process will be sent to all proposers in late July 2025.
What's New for Cycle 33
See HST New and Important Features.
Where to Get Help
- Read this Call for Proposals and The Hubble Space Telescope Primer for Cycle 33.
- Visit the STScI HST Phase I Proposal Roadmap and the HST Phase II Proposal Roadmap.
- Visit STScI’s website at http://www.stsci.edu/.
- Register (or review/check) a STScI Single Sign-On (SSO) Account.
- Contact the STScI HST Help Desk (web: https://hsthelp.stsci.edu).
Who's Responsible
The HST Call for Proposals and related materials for Cycle 33 were edited by Molly Peeples (Hubble Science Policies Deputy). The Associate Director for Science, Mercedes López-Morales, and the Science Mission Office (SMO) at STScI are responsible for the oversight of the HST science program selection process. SMO members include Marc Postman (SMO Mission Head), Laura Watkins (SMO Deputy Mission Head), Claus Leitherer (Hubble Science Policies Lead), Katey Alatalo, Daniel D'Orazio, Andrew Fruchter, Amy Jones, Susan Kassin, Rebecca Levy, Amaya Moro-Martin, Nikolay Nikolov, Jamila Pegues, Linda Smith, and Technical Manager Aleksandra Hamanowicz. Neill Reid (Multi-Mission Project Scientist) participates in an advisory capacity.
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