HST programs are selected through competitive peer review. A broad range of scientists from the international astronomical community evaluates and ranks all submitted proposals, using a well-defined set of criteria (see Section 6.2) and paying special attention to any potential conflicts of interest. The review panels and the Telescope Allocation Committee (TAC) offer their recommendations to the STScI Director. Based on these recommendations, the STScI Director makes the final allocation of observing time.
The review panels will consider Small GO (1-34 orbits; Section 3.2.1), Medium GO (35-74 orbits;
Section 3.2.2), Calibration GO (
Section 3.2.4), Snapshot (
Section 3.3), Regular AR (
Section 3.4.1), Calibration AR (
Section 3.4.3) and Theory (
Section 3.4.4) Proposals. Each review panel has an allocation of a specific number of orbits, and the panel can recommend Small GO Proposals up to its orbit allocation. Medium GO Proposals will be ranked side-by-side with the Small Proposals, but the panels will not be charged for them; instead, each panel will be allocated a fixed number of medium proposals, depending on the overall medium proposal pressure within that panel. The panel recommendations generally do not require further approval of the TAC (
Section 6.1.2), and scientific balance will be determined within each panel rather than by the TAC. The panels do not adjudicate Large GO (
Section 3.2.3), Treasury GO (
Section 3.2.6), or AR Legacy Proposals (
Section 3.4.2), but they will send comments on these proposals to the TAC for their consideration.
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). In Cycle 24, we anticipate having a panel dealing with
Solar System, two panels dealing with
Planets (including exoplanets, planet formation, and debris disks); three panels dealing with
Stars (of any temperature and evolutionary state, and including nearby star formation and Galactic ISM); two panels dealing with
Stellar Populations (resolved); three panels dealing with
Galaxies (including unresolved stellar populations and ISM in external galaxies); two panels dealing with
Massive Black Holes and Hosts (including AGN and Quasars); and two panels dealing with
IGM and Cosmology (including large-scale structure, gravitational lensing, and galaxy groups and clusters). 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.
The TAC will include the TAC chair, the fourteen panel chairs, and three at-large members to ensure broad expertise across the full range of scientific categories. The primary responsibility of the TAC is to review Large GO (Section 3.2.3), Treasury GO (
Section 3.2.6), and AR Legacy Proposals (
Section 3.4.2), and any other particularly large requests of resources (GO Calibration, SNAP, Theory, or Pure Parallel Proposals). The TAC will also consider the panel recommendations concerning the Medium Proposals (35-74 orbits, see
Section 3.2.2), will rank accepted Pure Parallel Proposals, and will be the arbiter of any extraordinary or cross-panel issues.
