Guidelines for External Panelists


GO proposals requesting less than 16 orbits, regular Archival (AR), Theory and Snapshot (SNAP) proposals are distributed for external review. Remember that HST proposals can request observing time and funding. GO proposals typically request both. Archival and Theory proposals request only funding, no observing time. Snapshot proposals are filler programs, typically only a random subset of the proposed targets are observed and the science case should be crafted accordingly.

Those proposals are assessed by five experts who grade on an absolute scale against the primary criteria: scientific merit within the field, broader importance for astronomy & the strength of the data analysis plan (where applicable); HST’s unique capabilities must also be required to achieve the scientific goals. Each external panelist receives a limited number of proposals. Panelists grade those proposals using the Selection Criteria and Scoring System and provide Proposal Feedback Comments.

The proposals will be grouped by subject area, matching the virtual panels. The averaged grades from the external reviewers will be combined for each proposal to give a ranked list. The rank ordered list from each subject area will be provided to the chair of the appropriate virtual panel prior to the meeting to allow the identification of potential conflicts. In addition, the chairs will have an opportunity to flag proposals with divergent grades for discussion by the virtual panel.

Cycle 29 External Panelist Schedule

May 3
  • Receive proposal notifications.
  • Log in to the SPIRIT reviewer tool.
  • Identify proposal assignments.
  • Check for Conflicts of Interest.
Throughout May
May 7
May 10
  • Attend virtual panel orientation meeting.
June 4
  • Deadline for submitting grades and feedback comments.

Conflicts of Interest

Panelists should let the Science Policies Group know if they believe they have Conflicts of Interest with any proposals in their initial assignment. Those proposals will be re-assigned.


Reviewers must provide Proposal Feedback Comments for each proposal they are assigned, panelists should review the guidelines for providing this feedback. The comments submitted by external reviewers will be forwarded directly to the proposers. Reviewers must therefore take appropriate care in framing their responses.


All HST Phase I proposals and documents related to the proposal review are strictly confidential. Panelists should review the Confidentiality information.

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