Proposal Review Getting Started Guide

A general guide to getting started with the HST Cycle 29 Proposal Review.

(tick) Know the HST Cycle 29 Telescope Allocation Committee (TAC) Timeline

Friday, April 9, 2021Cycle 29 Proposal Deadline
Monday, May 3, 2021
  • STScI releases proposals to panelists for review.
    • Virtual panelists should provide preliminary grades.
    • External panelists should provide final grades and brief reports.
Tuesday, May 4, 2021Orientation meeting for Panel Chairs and Vice Chairs.
Thursday, May 6, 2021Orientation meeting for Virtual Panelists.
Friday, May 7, 2021Deadline for all panelists to identify conflicts of interest and to recommend proposals that should be moved to another Science Category.
Monday, May 10, 2021Orientation meeting for External Panelists.

Wednesday, June 2, 2021

Deadline for Virtual panelists to submit preliminary grades for proposals that they are assigned.

Friday, June 4, 2021Deadline for External panelists to submit grades and feedback comments for proposals that they are assigned.
Friday, June 4, 2021
  • STScI sends each Virtual panelist the list of proposals to be discussed by their panel.
  • Virtual panelists should review all proposals listed (especially those they did not read for preliminary grading) in preparation for the panel meeting.
  • Virtual panelists should also consider whether they wish to raise a triaged proposal for discussion.
Wednesday, June 9, 2021Deadline for Executive Committee to submit preliminary grades for Large and Treasury proposals that they are assigned.
Tuesday, June 15, 2021
  • STScI releases the list of proposals that will be discussed in the Executive Committee meeting.
  • Executive Committee members should review all those proposals in preparation for the panel meeting.
Wed - Fri June 16 - 18, 2021Virtual panels meet.
Mon - Wed June 21 - 23, 2021Executive Committee meets.
Friday, June 25, 2021Deadline for Panel Chairs to submit final consensus reports.
Friday, July 2, 2021STScI releases Cycle 29 Science Program.

(tick) An Overview of the TAC Process

The procedures for reviewing HST proposals are as follows:

Small GO proposals for less than 16 orbits, regular Archival and Snapshot proposals are distributed for external review. Those proposals will be assessed by five experts who will 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 will receive a limited number of proposals. The proposals will be grouped by subject area, matching the virtual panels. 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. Each panel has a specific allocation of orbits for Small (<16 orbit) GO proposals.

The remaining proposals are reviewed through a two stage process. Small GO proposals for 16-34 orbits and Medium GO proposals are reviewed by the TAC panels. Each panel has a specific allocation of orbits for Small (16-34 orbit) GO programs and a separate allocation for Medium GO programs.  In the first stage, panelists submit preliminary grades and comments on a set of proposals before the TAC meeting. Proposals that score highly on their preliminary grades will advance to the next stage of the review. In the second stage, the panels discuss and grade each of the remaining proposals and come to a consensus evaluation used to provide a ranked list.

During preliminary grading, each proposal is assigned 6 reviewers to provide sufficient basis to determine an initial proposal ranking; the lowest ranked proposals are flagged (triaged) and will not be discussed during the panel meeting unless explicitly resurrected. The in-person discussion is organized by the Panel Chair and Vice-Chair who do not grade panel proposals; the Vice-Chair deputizes for the Chair in case of conflicts (except for Solar System). During the meeting, the Primary and Secondary Reviewers for each proposal lead the discussion, and all of the panelists are expected to contribute to that discussion. Therefore, each panelist should read carefully all of the proposals that will be discussed at the panel meeting. STScI may adjust assignments for Primary and Secondary Reviewers after triage to balance the work load among panelists. Each panel compiles a single ranked list, including both the Small (16-34 orbit) and Medium GO proposals. The cutoff limit is set by the panel allocation of orbits for Small (16-34 orbit) GO programs.

Large and Treasury GO proposals and Legacy Archival proposals follow a similar process, but are discussed by the Executive Committee after the topical panels have completed their evaluations. The Executive Committee comprises the Panel Chairs & Vice-Chairs and At-Large TAC members, and is led by the TAC Chair. Panel Chairs/Vice-Chairs serve as Primary and Secondary Reviewers for the Executive Committee. Panelists provide comments on the Large and Treasury proposals within their topical areas to help the Panel Chairs & Vice-Chairs present a thorough review of each proposal. At-Large TAC members are not assigned to individual panels, but can step in to deputize for Panel Chairs in case of proposal conflicts. They serve as regular members of the Executive Committee.

(tick) Become Familiar with the Call for Proposals

The HST Cycle 29 TAC recommends a Science Program to the STScI Director in response to the Call for Proposals. STScI has solicited General Observer, Snapshot and Archival Proposals.

General Observer proposals are divided into categories primarily based on their size (Small, Medium or Large). However, they are also flagged as Joint Observing Programs if they require Chandra, TESS, NOIRLab, NRAO, or XMM time to complete their science goals, a Calibration proposal if the observations will lead to an improved calibration of the facility for the community, a Treasury  proposal if the proposal addresses multiple science questions and the team plans to provide high level science products, or a Long-Term Status Proposal if the observations are spread over Cycle 29 and subsequent cycles. Snapshot (SNAP) proposals are programs that can fill space in the HST observing schedule, there is no guarantee how many or which targets will be observed.

Archival (AR) proposals are divided into categories. Regular and Legacy AR proposals support analysis of HST data that will be public by the start of Cycle 29. Theory proposals support theoretical and computational research that is relevant to HST. Calibration AR proposals support analysis of Calibration data that will already be available in Cycle 29. Finally, Cloud Computation Studies will take advantage of the availability of HST data on Amazon Web Services (AWS) for large-scale data analyses.

(tick) Become Familiar with Dual Anonymous Reviews

Peer review of HST Cycle 29 General Observer proposals will be Dual Anonymous. At the time of the review, proposers will not know the identities of panel members and panel members will not know the identities of the proposal teams. The community has successfully used the Dual Anonymous review process for HST General Observer Cycles 26 - 28, NuSTAR Cycle 6, JWST Cycle 1 and other NASA reviews. For more information, about the Dual Anonymous review, please review the Anonymous Proposal Reviews page.

(tick) Become Familiar with Panel Roles and Responsibilities

Each topical panel consists of one Panel Chair and Vice Chair (except for Solar System) who will organize and lead the discussion of the proposals, 8-10 Panel Members who will review the proposals and draft consensus feedback briefly summarizing the proposal and explaining the strengths and weaknesses discussed by the panel, a Panel Support Scientist who assists the Panel Chair with administrative aspects of the panel review, and a Leveler who is dedicated to keeping the panel discussion focused on the scientific strengths and weaknesses.

Panel Members play one of several roles for each proposal, depending on the subject of the proposal and the expertise of the Panel Member:

  • The Primary Reviewer submits preliminary grades and leads the discussion at the panel meeting
  • A Secondary Reviewer submits preliminary grades and supports the discussion at the panel meeting
  • A Reviewer submits preliminary grades and contributes to the discussion at the panel meeting
  • All panelists discuss all proposals (unless they are conflicted) at the panel meeting.
  • If you are Not Assigned a formal role to a proposal for preliminary grading, please familiarize yourself with the proposal so that you can contribute to the discussion at the meeting

Panel members also review a subset of the Large/Treasury/Legacy proposals. They do not grade those proposals but provide the Chair and Vice-Chair with feedback on their strengths and weaknesses to aid the later discussion.

(tick) Download Proposals and Submit Preliminary Grades

STScI has developed the web-based SPIRIT tool to facilitate preliminary grading of the proposals before the TAC meeting and final grading of the proposals during the TAC meeting. Grading assignments can be viewed in SPIRIT ( A Quick Guide to SPIRIT (Reviewer Tool) can be downloaded here.

Panelists are required to provide three grades for each proposal matched against the following criteria:

  1. The scientific merit of the program and its potential contribution to the advancement of scientific knowledge;
  2. The program’s importance to astronomy in general. This should be stated explicitly in the “Scientific Justification” section of the proposal;
  3. A demonstration that the unique capabilities of HST are required to achieve the science goals of the program.

The final grade is the straight average of those values.

Panelists do NOT need to provide a complexity rating for proposals.

(tick) The TAC Meeting

Panel members should come prepared to discuss each of the proposals that are to be discussed at the TAC meeting. After the discussions of individual proposals, each topical panel will rank the proposals in the panel, paying close attention to proposals near the cut-off to award telescope time. Typically, panels rank the proposals to twice the amount of time allocated in case the telescope has unforeseen technical problems. Once the panel agrees on the proposal ranking, then the Primary reviewer is responsible for drafting the panel consensus evaluation with the help of the Secondary Reviewer and other Reviewers. Once the Panel Chair signs off on the panel consensus evaluations, then the work of the Panel Members is complete.

(tick) Getting Help

Please contact the HST Help Desk ( for any questions that you may have, including questions about science policy or technical performance. In your correspondence, please identify yourself as a TAC member. If your question is about a specific proposal, please state the ID for the proposal associated with your question.

Next: Overview