sci20001 — Announcement

Of Proposals and Papers — The Success of the European Community in the Scientific Utilisation of the Hubble Mission

22 June 2020

Every year we await with anticipation the results of the Hubble time allocation review. This year the Cycle 28 Time Allocation Committee (TAC) met on 11–15 May 2020. Because of Covid-19 the meeting was held remotely, with astronomers participating from countries spanning several time zones. The European presence on the review panels — as panelists, chairs and TAC members — was, as always, significant. Again this cycle, the proposal review process was dual-anonymous, with the identities of the proposing team concealed from reviewers. The virtual meeting went extremely well and produced an exciting scientific program that the STScI Director endorsed. Approximately 2800 orbits were allocated to successful proposals, with a proposal pressure of 1/6 for proposals and 1/8 for orbits in the General Observer category.

ESA Member State astronomers were quite successful in this cycle also, obtaining 23.6% of the proposals, and 19.4% of the orbits. ESA Co-Is were 32.4% of the total number of Co-Is, showcasing the high level of engagement of the European community in the Hubble mission.

The NASA-ESA Memorandum of Understanding for the Hubble mission states a guaranteed access to 15% of the allocated Hubble observing time, over the duration of the mission. In the 30 years of Hubble scientific operations, European astronomers have always won more than the stipulated fraction, in very competitive reviews.

In Cycle 28, most of the successful observations require WFC3 (47.2%), followed by STIS (20.5%), COS (18.9%) and ACS (13.5%). Of interest, 33% of Principal Investigators (PI) were first time PIs — to the next generation of Hubble users, welcome!

The final scientific program for Cycle 28, now public, is broad and reflects the versatility of the Hubble observatory, able to produce breakthrough results in a variety of diverse astronomical fields. Trending scientific topics in Cycle 28 were galaxies, exoplanets, stellar physics and supermassive black holes.

We look forward to seeing how these new ideas will generate unique datasets that will enrich the Hubble Archive, and will produce exciting results that will be published in professional astronomical journals.

The success of the mission, and of the community, is also shown by the number of publications that are based on Hubble data. According to Apai et al. (2010), the philosophy behind the Hubble article classification is to include only those articles that present analysis of HST data to reach a scientific conclusion. With this assumption, we counted 17 361 refereed papers based on Hubble data over the lifetime of the mission, of which 1014 in 2019 (Fig. 1). For the first time, in 2019, Hubble passed the magic number of 1000 publications in one year.

Almost half of the 2019 Hubble publications (401, ~ 40%!) were authored by a European astronomer. In the graph above we see the distribution across the various categories of publications. In light green we show papers based on new observations (GO), while in purple we show publications based on purely archival data. Yellow indicates papers that are based on both new and archival data. A small number of Hubble-based publications cannot be easily placed into any of these categories and they are shown in dark green.

Most interestingly, the number of pure archival papers equals the number of papers based on new observations. This speaks volumes to the benefits of having a reliable data archive which is continuously augmented by new observations. With a baseline of 30 + years, new scientific studies are enabled by the powerful combination of new and archival observations. For European astronomers this is a true success story, as they are responsible for 37% of the Hubble papers based on new observations, and 43% of those based on archival data.

The community of Hubble users in Europe is large: 2770 out of ~ 8000 users worldwide, and growing year on year. It is also very engaged and dedicated, and as we have shown here it is very successful. I look forward to seeing what they will be able to do with both Hubble and Webb operating together. Can’t wait for that time to come.


Antonella Nota
ESA/HST & ESA/JWST Project Scientist
STScI Baltimore, USA

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