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STUC Update

The Hubble Space Telescope Users Committee is a group of 12 scientists who represent the interests of the Hubble user community. The STUC meets twice a year, and most recently we met in May 2022. This meeting was the first in-person meeting since 2019, given the COVID-19 pandemic which previously forced STUC meetings to online-only affairs. It was great to be able to meet everyone in person once again at STScI, and we all carefully ensured that COVID-19 safety protocols were strictly followed, to ensure the safety of all attending.

During the two-day meeting, the STUC heard presentations on the status of the Hubble itself, its operations and the running of the observing and proposing program. We also heard updates on the various science programs collecting data that will provide a huge legacy for Hubble itself and be a crucial community resource. Regarding Hubble operations, the STUC continues to be impressed by the improvements that continue to be made to the mission despite its 30+ year lifetime. These include efforts to increase the lifetime of the Cosmic Origins Spectrograph (COS), a new spectropolarimetry mode for the Advanced Camera for Surveys (ACS) and the development of machine-learning algorithms to help identify and mitigate "ghosts" seen in Wide Field Camera 3 (WFC3) UV Imaging Spectrograph (UVIS) data. The development of Jupyter Notebooks for analyzing Space Telescope Imaging Spectrograph (STIS) data provides the community with great guidance on how to process data using the increasingly popular Python-based system.

Although Hubble suffered issues with its onboard electronics, forcing the switch from "Side B" to the redundant "Side A" electronics, the STUC was impressed by the efforts to fix the "Side B" electronics. The primary concern of the STUC is the reliability of the onboard gyros, which in the past have experienced failures, although we note that loss of one or even two of the three remaining gyros would not be a mission-ending event, although it may reduce scheduling flexibility.

The STUC was presented with an update on the Cycle 29 midcycle and Cycle 30 of the General Observer (GO) program. The use of dual-anonymous reviewing, pioneered by Hubble, continues to pay dividends in diversifying the PIs of accepted programs. Due to the need to review large numbers of proposals, a hybrid approach is taken when reviewing, with smaller (<16 orbits) GO proposals mostly being reviewed by external panelists, with larger programs reviewed "face-to-face" with some triaging from preliminary grades. These steps are necessary in order to manage the large number (1,062 in Cycle 30) proposals received, and the STUC was happy that the review process was both efficient and fair.

The May STUC meeting saw a change in leadership for the ESA/HST program, with Dr. Chris Evans taking over the role of ESA HST Project Scientist from Dr. Antonella Nota. Dr. Paule Sonnentrucker is now both the ESA HST and JWST Mission Manager. The ESA community continues to be vitally important for Hubble, with 20% of proposals in Cycle 30 coming from scientists from ESA member states. ESA/HST also has a strong public outreach program, including submitting HST content to the popular Giphy website, and the ESASky website provides an excellent and easy way for people to explore Hubble and other astronomy data with the click of a mouse.

The STUC heard about progress on the "Hubble UV Legacy Library of Young Stars as Essential Standards" (ULLYSES) project, a large (1,000 orbit) observing program to create a UV spectroscopy library of young high- and low-mass stars. Observations for the ULLYSES program are now 72% complete, however it is noted that a larger-than-expected number of observations needed to be repeated due to issues with the observations. However, overall the STUC is very impressed by this program, the scope of which can only be performed as part of Director's Discretionary Time (DDT).

Given the increased interest in Time Domain Astrophysics and Multi-Messenger Astrophysics (TDAMM), there has been increased pressure on Hubble to perform rapid turnaround Target of Opportunity (TOO) observations. The upcoming LIGO/Virgo/KAGRA O4 run in 2023 will likely increase this pressure. However, due to the highly constrained nature of many Hubble observations, and how disruptive TOOs can be to critical observation programs, these TOOs can be difficult to schedule. The STUC was presented with a novel concept in how to handle this: Designating one Thursday a month as "constraint free." This would allow observations on this day to be bumped, without causing major interruptions to programs where loss of a single observation would be of too high an impact. The concept would be that TOO requests for this day can be scheduled 2–5 days before the designated Thursday, with a deadline of 6 a.m. EST on the Tuesday preceding the constraint-free Thursday. The STUC was supportive of this idea, but wanted a better idea of how it would likely be utilized.

The STUC was presented with implementation concepts for reducing the default Exclusive Access Period (EAP) of Hubble GO data from the current six months for Small and Medium programs to zero months, i.e., having data becoming public immediately. This proposed change came from the STScI Director, within the context of recent changes in NASA's Science Information Policy (SPD‑41). Though Hubble and JWST are not required to follow this policy at this time, it was presented that Hubble would show leadership by following the recommendation to make data public. Large and Treasury programs already have zero EAP. Under the proposed change, proposers would be able to request a non-zero EAP if necessary.

The STUC noted that although open data is generally a good thing, EAPs may protect early-career researchers. The STUC also wanted clarification on how exceptions would be judged by panels or by STScI. For these reasons, the STUC did not recommend moving to zero EAP in Cycle 31, instead recommending a period of community outreach to gauge community feeling on this. The Science Policies Group has since confirmed that no changes will be made to the EAP this cycle, and that they will be working with the STUC and the JWST STUC (JSTUC) to survey the community regarding the Hubble and JWST exclusive access periods within the coming months.

Finally, given the success of the ULLYSES project, the STUC recommended that the STScI Director start looking towards the definition of the next large DDT project, a process that should start with requests for community input on a program that will be a defining achievement for the final years of the mission.

The full STUC report, presentations to the STUC, and STUC membership list can be found on the Space Telescope Users Committee page.