Hubble Cycle 18 Proposal Selection

The TAC and the panels in Cycle 18 had 2,600 orbits available for allocation. Of these, 2,000 were made available to the panels, and 600 to the TAC. This allocation is smaller than in the previous cycle, due to the allocation of orbits to the (1) Multi-Cycle Treasury Program, (2) remaining COS GTO orbits, and (3) unexecuted Cycle 16 and 17 programs. The oversubscription ratio was 9:1 by orbits, which translated into a proposal acceptance rate of one out of six.

The acceptance rate for archival research was about one out of three, similar to the long-term average.

Quite a few observing proposals fell into the medium category (40–99 orbits), making them quite expensive, but still too small to fall into the large category (100+ orbits). In prior cycles, a “subsidy” was given to medium proposals, meaning that—if such a proposal were approved—the panel would be charged fewer orbits than the number requested. The subsidy is taken from a central pool. In Cycle 18, because of the large oversubscription and the relatively smaller number of orbits available to the panels, there was a concern that—even with the subsidy available—the panels would be hesitant to support any of the medium proposals. To guarantee the approval of at least some scientifically outstanding, medium proposals, 300 orbits from the panel allocation were set aside for them, in lieu of a panel subsidy. Out of this pool, the panel chairs of each set of mirror panels could allocate orbits to their top-ranked medium proposals. We have requested feedback from the panelists on the merits of this approach, in order to develop the process to be used for Cycle 19.

Our policy for handling conflicts of interest remained unchanged from Cycle 17, when we defined co-investigators (Co-Is) who are close collaborators to be minor conflicts. Similarly, institutional conflicts were considered to be minor.  When a minor conflict arises, the panelist may, at the chair’s discretion, participate in the proposal discussion—but must not cast a vote. Striking a balance between minimizing conflicts of interest and maximizing the expertise of a panel is becoming increasingly challenging as collaborations expand and proposals grow in size. We found our rules led to a healthier discussion in the panels, with no evidence for bias.

Summary of Cycle 18 Results

ProposalsRequestedApproved% AcceptedESA
General Observer  872 14616.7% 3020.5%
Snapshot   51   917.6%  333.3%
Archival Research   75  2634.7%  0
AR Legacy   10   220.0%  0
Theory   43  1330.2%  0
Total 1051 19618.6% 3316.8%
Primary Orbits23096 2578*11.2%38214.8%
*Does not include 16 Calibration orbits (9 Prime + 7 Internals)