6.1 How STScI Evaluates Submitted Proposals

HST Programs are selected through competitive peer review. A broad range of scientists from the international astronomical community evaluates all submitted proposals, using a well-defined set of criteria (see Section 6.2). They rank the proposals and offer their recommendations to the STScI Director. Based on these recommendations, the STScI Director makes the final allocation of observing time.

6.1.1 The Review Panels

Review panels will consider Regular GO (fewer than 100 orbits; see Section 3.2.1), SNAP, Regular AR, and Theory proposals. Each review panel can recommend Regular GO proposals up to a certain limited number of orbits that it has been allocated. In order to encourage the acceptance of larger proposals, a progressive orbit "subsidy" is allocated to the panels, with orbits in the subsidy coming from outside the direct panel allotment. The algorithm for this "subsidy" has the goal of creating an acceptance rate of submitted programs that is approximately independent of size.

The panel recommendations generally do not require further approval of the TAC (see Section 6.1.2) and scientific balance will be determined within each panel rather than by the TAC. The panels do not decide on Large GO proposals (100 orbits or more; see Section 3.2.4), Treasury GO proposals (see Section 3.2.4), or AR Legacy proposals (see Section 3.4.2), but they will send their comments on these proposals to the TAC for their consideration. Calibration proposals (see Section 3.6) will only be reviewed by the TAC.

Panelists are chosen based on their expertise in one or more of the areas under review by the panel. Each panel spans several scientific categories (as defined in Section 8.8). For example, in Cycle 12 there were three panels dealing with Hot Stars, ISM and Circumstellar Medium; two panels dealing with Star Formation, Cool Stars and Stellar Populations; three panels dealing with Galaxies, AGN and Quasars; two panels dealing with Quasar Absorption Lines and Cosmology; and one panel dealing with the Solar System. The division of scientific categories over panels may be different in Cycle 13, but the breadth of the panels will remain the same. Within a panel, proposals are assigned to individual expert reviewers based on the keywords given in the proposal (see Section 8.9). These keywords should therefore be chosen with care.

Given the breadth of the panels, proposers should frame their scientific justification in terms appropriate for a panel with a broad range of astronomical expertise.

6.1.2 The Telescope Allocation Committee (TAC)

The TAC will be composed of a TAC chair and the panel chairs. The primary responsibility of the TAC is to review the Large GO proposals (100 orbits or more; see Section 3.2.2), Treasury GO proposals (see Section 3.2.4), AR Legacy proposals (see Section 3.4.2), any other particularly large requests of resources (SNAP, AR, Theory or pure parallel), and Calibration proposals (see Section 3.6). It will also be the arbiter of any extraordinary or cross-panel issues.