About this Article

The Space Telescope Users Committee (STUC) met in person on December 5 and 6, 2024. Several topics were covered, including mission status, new opportunities for Cycle 33, and updates on the budget process for Hubble. The observatory continues to operate with extraordinary scientific productivity. Three STUC members have completed their term on the committee, and we are grateful for their contributions: Jeyhan Kartaltepe (Rochester Institute of Technology), Hannah Wakeford (Bristol), and Mike Wong (Berkeley). We encourage the community to view the presentation slides on the STScI website. The STUC will also write a full report with recommendations based on the information presented.

Ongoing Success

The Hubble Space Telescope is operating with extraordinary success, excelling by every metric of evaluation. It is in the golden age of scientific productivity, with a record publication in 2023 of 1056 journal articles, increasing the number of publications from both new and archival observations. Demand for Hubble observing time remains high with an over-subscription of 6:1 in Cycle 32.

The transition to Reduced Gyro Mode (RGM) has gone extremely well. Observing efficiency has returned to 70+ orbits per week (only a 10-15% reduction from three-gyro mode), though the instantaneous field of regard is reduced to about 50%, similar to JWST (the full sky remains available over the course of a year). Gyro-6 is in the pointing control loop, with the highly reliable gyro-4 as a powered back-up. Gyro-3, which had been unreliable, is powered on and monitored for potential future use. The science data quality is unchanged since 1-gyro guiding during science observations has been in place since 2021 (in particular, RGM does not degrade the precision of exoplanet transits).

All instruments are operating nominally and observatory subsystems are expected to be reliable into the next decade, with increased success probabilities when planned redundancies in the science instrument command & data handler are restored in 2025. Re-entry date predictions are updated regularly with the most recent predictions having less than 10% probability of re-entry before December 2029, and a median re-entry date of August 2033, even if no intervention is done. Similarly, the Tracking and Data Relay Satellite system is expected to be reliable for more than 5 years, ​​and mitigations are possible beyond the five-year horizon. Despite these successes, significant reduction of the budget put Hubble’s future operations (including potential cuts to instrument modes), science impact, and productivity in peril.

The last six months have brought several major breakthroughs enabled because of Hubble’s ever-growing long-time baselines and continued coordination with JWST. Hubble's long-time baseline enables science from the Outer Planet Atmospheres Legacy (OPAL) program in particular, with over 65 publications based on a decade of data covering dark spots on Neptune, seasonal polar hazes on Uranus, spokes in Saturn's rings and subtle color changes in the cloud bands, and variable winds and storms on Jupiter. The decades-long time baselines also have enabled unprecedented discoveries of the first-known intermediate-mass black hole, in the globular cluster ω Centauri, and the existence of more – and more massive than expected – flickering black holes in the early Universe revealed in Hubble’s Ultra-Deep Field. Hubble and JWST have teamed up to observe the circumstellar disk around the visible-eye star Vega, finding it to be smoother than expected, showcasing the lack of large planets there. The STUC continues to be impressed by the novel ways the community is leveraging the strengths and unique capabilities of Hubble to do previously unimaginable science.

Senior Review Process

STScI provided an update on the continuing evolution of the budget situation. The Fiscal Year (FY) 2025 budget was set below the historical norm, but at a level high enough to continue operations and support for all modes in Cycle 32. However, grant funding was constrained to a level close to Cycle 31 and could not return to historical values. Funding for general outreach and social media activities at STScI, as well as the Hubblesite.org website hosting all Hubble news releases, was terminated. In addition, Hubble continues to be directed to fully support the Hubble-Einstein-Sagan fellows within the observatory budget. Future budget decisions will be informed by the outcome of the 2025 Senior Review of NASA’s operating missions. The review is held every three years to evaluate NASA missions in their extended phase of operations. The outcome of the Senior Review is expected in late Spring 2025, in time for the next budget cycle. 

As part of the 2025 senior review, Hubble was directed to submit a budget that meets the levels set in the most recent President’s Budget Request, which was considerably (>20%) lower than the cost of continuing operations and grant funding without changes. In response to community input, Hubble submitted a proposal that would continue operations of all instrument modes in the near term, but with ACS/WFC and WFC3/IR offered as shared-risk. These modes would receive no observer support and minimal calibration support (ACS/WFC anneals, superbias and superdark updates would be performed, but no other calibration file would be updated; WFC3/IR calibration files and pipeline would not be updated). STScI is investigating the impact of minimal support on the science quality of the data, and expectations are that the degradation in calibration accuracy would be small enough to continue enabling impactful science for ~3 years. The nominal budget request would support reduced grant funding, but significantly (~30%) below the Cycle 32 value. Grants would be determined by a formula, rather than peer review. Outreach activities at GSFC and STScI would be reduced. High level science product (HLSP) development would be reduced, but STScI would continue to maintain and ingest all HLSPs (including HAP, HASP, community-provided HLSPs, and HLSPs from large Director Discretionary programs, such as Frontier Fields and ULLYSES). Mission risk would also increase as staff expert in responding to unexpected failures would be removed.

The Cycle 33 Call for Proposals reflects this budget scenario. STScI submitted an additional request for increased funding, which would be prioritized to restore grants, support for instrument modes, risk posture, and outreach, depending on the level of a potential funding increase.

Community Advocacy

We encourage the US community to get involved in helping advocate for NASA astrophysics and science. While this advocacy can and should showcase many of Hubble’s strengths and its high productivity, we encourage the community to center their advocacy messages around strong federal support for NASA science as a whole. Below, we offer suggestions for possible ways to begin doing this, but we also encourage the community to take advantage of additional opportunities that may present themselves.

• Attend the next meeting of the NASA Astrophysics Advisory Committee (APAC) and submit a public comment.
• Get involved with the AAS Committee on Astronomy and Public Policy (CAPP).
• Attend public policy events and sessions at the next AAS meeting. At the 2025 winter meeting AAS #245, these include the NASA Townhall, the STScI Townhall, and the special session on Policy and Advocacy for the Astronomical Sciences in 2025. 
• Invite a member of the AAS Public Policy team to give a policy talk at an upcoming colloquium or seminar.
• If you are an AAS member and eligible to vote in the US, consider applying to take part in a future AAS Congressional Visits Day to speak directly with your elected representatives and their staff on Capitol Hill.
• Work with your campus Government Relations office to set up a local, in-district meeting with one or more of your elected representatives when they are on recess. Note that the AAS Public Policy team is also available to help support local visits.

New in Cycle 33 

The Cycle 33 Call for Proposals was released on December 18. This will be the first cycle with shorter page limits for all proposal categories, in line with the new guidelines for JWST proposals. Budgetary constraints have also led to a restructuring in how AR funds are allocated, and to a pause in Legacy AR programs. Finally, several new initiatives will be implemented in the Cycle 33. They are: 

Long-term monitoring: This initiative serves to highlight Hubble's longevity and its importance for time-domain astronomy, and also allows proposals to request multiple observations over up to 5 cycles. Proposers should justify the need in the special requirements section of the proposal and check the long-term monitoring box in the APT.

Roman Preparatory Science: As was done for JWST, there is a call for Roman Preparatory Proposals. These are indicated with a checkbox in the APT. There is no exclusive access period for these data (as was the case with, for example, JWST preparatory science some cycles back) because this is a service to the community and there will be no exclusive access period for Roman data. 

Discovery Director's Discretionary Time (Discovery DDT) Programs: This is an extended DDT program that provides more avenues for timely follow-up of exciting discoveries. Midcycle proposals will not be offered in the future, so this pathway provides a channel to get data on exciting, timely programs and those that will significantly accelerate the pace of scientific progress even if they can nominally wait for the next call for proposals. Discovery DDT programs will ideally be <10 orbits. 

Community Target of Opportunity (ToO) Programs: A new initiative that may begin observations during Cycle 33 is the Community Target of Opportunity (ToO). These are designed for exciting, high-impact science that is unlikely to trigger but essential to observe with Hubble and Webb. The community will identify the science cases, ideally about 3, through White Paper submissions. Selected programs will be designed by the community and will stay in the queue until they execute. 

The Success of Dual Anonymous Peer Review

Dual Anonymous Peer Review (DAPR) was introduced for Hubble Cycle 26 proposals in 2018. The main goal was to spotlight scientific merit as the key criterion for evaluation, focusing reviews and panel discussion on the proposal, not the proposers. While there has been an adjustment period for the community accustomed to the way proposals have traditionally been written, that transition has largely been completed, with only a handful of issues in each proposal cycle. Especially exciting is the five-fold increase in the rate of new HST PIs (from ~6% to ~30% new PIs per cycle) after the implementation of DAPR.

Feedback

We encourage the community to provide feedback to STScI and to the STUC. Comments to the STUC chair can be made via the link on the STUC webpage.

Serve on the STUC

Would you like to serve on the STUC? Nominations for STUC membership can be submitted at any time by email to stuc-nominations@stsci.edu. Self-nomination is welcome, but not required. Submissions are encouraged, but not required, to include a cover letter and a one-page curriculum vitae summarizing the nominee’s relevant background and HST-related interests. While members must be affiliated with institutions in the U.S. or in ESA countries, there is no restriction on citizenship. Nominations will be considered on a rolling basis, as several members rotate off after every meeting, approximately every 6 months.