HST Duplication Policies for the TAC
There are two flavors of duplications: Target Duplications and Science Duplications.
These are observations of the same field of view using identical instrument configurations and comparable exposure times. By definition, observations using different instruments or filters are not duplications. Target Duplications are not allowed per policy. STScI uses software to identify duplications prior to the TAC meeting. The process checks for duplications of proposed targets with existing and planned current-cycle observations and between targets in the proposal pool of the TAC based on the submitted Phase 1 APT file. The proposals should have addressed any duplications with prior-cycle archival data. SPG notifies the Panel Chairs of any duplications among the recommended proposals, including the externally and virtually reviewed proposals, as well as the EC proposals. The Panels and the EC will recommend a resolution of the duplication, which could be a removal of the duplicating proposal or the individual target. If the duplication involves a single target in a Large proposal versus the same target that is the entire request in a Small program, the EC may consider just removing the target from the Large program. In some cases, duplications may be missed during the TAC meeting. These duplications will be resolved by the Director later in the process. Furthermore, a final, full Target Duplication check will be done in Phase 2.
These are dealt with by the TAC, both at the Panel and the EC level. In most cases, Science Duplications are an inefficient use of HST, and are undesirable. However, there is no policy prohibiting Science Duplications. During the TAC meeting, SPG staff will provide the Panel Chairs the recommended externally reviewed proposals. During the ranking phase of the Virtual Panel meeting, the Chairs may identify any overlapping science between the external and the top-ranked (above the 1 N line) discussion proposals. As the externally reviewed proposals are smaller and more limited in scope, Science Duplications should be extremely rare. In any case, the ranking of the externally reviewed proposals should not be changed, but the Panel may make a recommendation to the Director if they feel a modification is called for.
A similar process will be followed at the EC meeting. During the ranking phase of the EC proposals, the Chairs and Vice-Chairs will discuss any Science Duplications of top-ranked EC proposals with proposals in their respective panels. These are typically Medium proposals, whose scope may reach that of some EC proposals. The EC will make a recommendation if a genuine Science Duplication exists. The outcome could be a downgrade of an EC proposal if the recommended Panel proposal achieves identical science. Vice versa, the EC may find that a Large/Treasury proposal supersedes a recommended Panel proposal. In this case, the ranking of the EC proposal may stay the same. The EC should not rerank the proposals in the affected panel but inform the Director of the Science Duplication with the Panel proposal. The Director will decide about the reranking in the Panel.