Hubble Cycle 20 Proposal Selection

Andrew Fox, afox@stsci.edu, Claus Leitherer, leitherer@stsci.edu, & Brett Blacker, blacker@stsci.edu

Twenty-two years after launch, and three years after Servicing Mission 4, Hubble is operating with a full instrument capacity and continues to draw high demand for observing time. The Advanced Camera for Surveys (ACS), Cosmic Origins Spectrograph (COS), Fine Guidance Sensor (FGS), Space Telescope Imaging Spectrograph (STIS), and Wide Field Camera 3 (WFC3) are all operating successfully and were available for Hubble observing proposals in Cycle 20.

The Cycle 20 Call for Proposals was released in December 2011, and the Phase I deadline was February 24, 2012. As usual, although some proposals were submitted weeks before the deadline, the majority arrived on the last day, with a rapid rise in submission rate as the deadline, 8 p.m. eastern time, approached. We received a total of 1090 proposals, 83 more than in Cycle 19.

Review process

Hubble proposals are reviewed by members of the international astronomical community. In Cycle 20, reviewers were grouped into panels organized by science category. Each panel had one or more “mirrors,” so that proposals could be transferred to an alternate panel if needed to avoid conflicts. In Cycle 20, there were two Planets and Star Formation panels, three Stars panels, two Stellar Populations and Interstellar Medium panels, three Galaxies panels, two Active Galactic Nuclei and Intergalactic Medium panels, and two Cosmology panels, for a total of 14 panels. These panels reviewed four categories of proposals: Regular General Observer (GO), Archival (AR), Theory, and Snapshot (SNAP). Large GO, Treasury GO, and AR Legacy proposals were reviewed by the Time Allocation Committee (TAC), which consisted of the chairs of the 14 panels, three at-large TAC members, and the TAC chair. The at-large members have broad expertise and advised panels when additional perspective was needed to review a particular proposal.

The process of selecting the panelists began with the selection of the TAC chair about six months prior to the proposal deadline. Mario Mateo (University of Michigan) served as Chair of the Cycle 20 TAC. Next, we selected the chairs of the panels, the at-large TAC members, and the panel members. The recruitment of panelists was completed about four months prior to the proposal deadline. The primary consideration when constructing panels was to ensure each contained an appropriate range of scientific expertise to cover the relevant astronomical topics. Other considerations included ensuring a healthy mix of experienced senior panelists and younger postdoctoral panelists, gender balance, and appropriate representation of European Space Agency (ESA) member states and other countries. The final Cycle 20 review involved 132 panelists and TAC members.

All panels were close to the same size (9–10 members, including the chair) and were typically assigned between 60 and 90 proposals. The assignment of proposals to panels and to primary and secondary reviewers was based on matching the scientific keywords provided by the proposers and the reviewers, considering the balance of workload between panels, and minimizing conflicts of interest.