HST Guidelines and Checklist for Phase I Proposal Preparation

This page describes the formatting of Phase I proposals, the page limits for various types of proposals, and provides a checklist for proposers to consult when developing their observing proposals.

General Guidelines


The deadline for proposal submission is Tuesday March 26, 2024 at 8:00pm EDT. As part of the proposal submission process, proposers should submit a Team Expertise and Background section, following the instructions in HST Filling Out the APT Phase I Proposal Form We strongly recommend that proposers start preparing their proposals early in order to give themselves enough time to learn APT. Cycle 32 will use APT 2023.7.1, with an anticipated release by February 2024.

Proposals can be resubmitted up until the deadline.  Proposers are encouraged to submit well before the deadline whenever possible, to avoid possible last-minute hardware or overloading problems, or network delays/outages. Late proposals will not be considered.

Questions about policies and technical issues should be addressed to the STScI Helpdesk well before the deadline. While we attempt to answer all questions as rapidly as possible, we cannot guarantee a speedy response in the last week before the deadline.

Phase I Proposal Format

Cycle 32 Proposals must be submitted electronically. The Java-based APT (the Astronomer's Proposal Tool) is the interface for all Phase I and Phase II proposal submissions for HST.

A Phase I proposal consists of two parts:

Both are submitted to STScI directly from within APT. 

You are responsible for ensuring that your PDF upload does not include extraneous material (such as extra cover pages, team expertise statements, and backup material). Extraneous material that causes the proposal to exceed the page limits or violate requirements of Dual Anonymous Peer Review will lead to disqualification of the proposal without review.

Page Limits for PDF Attachment

There are page limits on the size of your PDF attachment. The table below outlines these limits for different proposal categories.

Table: Page Limits

Proposal Category1

Total Page Limit for PDF Attachment

Very Small GO8
Small GO8

Medium GO


Large GO


Treasury GO


Multi-Cycle Treasury GO


Regular AR8
Calibration AR8
Theory AR8

Legacy AR


1For Calibration GOJoint HST-Chandra, Joint HST/XMM-Newton, Joint HST-NOIRLab, Joint HST-TESS, and Joint HST-NRAO Proposals, users should determine whether their proposal is Small, Medium or Large based on the HST orbit request, and use the appropriate page limits. Mid-cycle and DD proposals are also required to follow these guidelines.

In relation to these page limits, note the following:

  • Proposals that exceed the page limits will be penalized in the review process; and risk being disqualified from the review in extreme cases.
  • There are no limits on the numbers of figures and tables in the PDF attachment, and they may be interspersed in the text. However, the total page limit must be observed.
  • References should be listed at the end of the proposal and do not count against the page limits. There are no restrictions on how references should be formatted.
  • Your PDF attachment must be prepared with a font size of 12pt. Do not change the format of any of the templates provided by STScI.
  • Proposals are not allowed to delete sections of the proposal, even if those sections are not used, unless our template files say those sections may be deleted.
  • While there are no specific page limits on the scientific justification, the strongest proposals will have a balance between scientific justification and the other required sections (such as the Description of Observations or the Analysis Plan) so that reviewers can accurately assess the merits and feasibility of a proposal using the selection criteria.
  • Historically, scientific justifications for different types of programs range from 3-6 pages (depending on proposal type). Based on feedback from the peer review process in previous cycles, we strongly recommend that proposals devote 3-6 pages (depending on proposal type) to the scientific justifications, and at least 1 page to the observing descriptions, to ensure that reviewers will have sufficient information to judge the science of the proposals during the peer review process.

Proposal Preparation Checklist

Table: Proposal Preparation Checklist 



1) Review the Phase I Roadmap

The HST Phase I Proposal Roadmap is a high level step-by-step guide to writing a Phase I proposal. It includes links to various documents and training videos.

2) Install APT

Go to the APT webpage. Follow the instructions there to download and install the latest version of APT onto your machine. You can also ask your system administrator to do an institution-wide installation.

3) Fill out the APT Phase I form

Use APT to fill out the Phase I form. Information on the use of APT, including movie tutorials, is available on the APT webpage. A description of which items are requested as well as guidelines for answers are presented in HST Filling Out the APT Phase I Proposal Form. Proposers can save work in progress, so APT submission can be completed over several sessions.

4) Download a template file for the creation of your PDF attachment

Download one of the templates to create your PDF attachment. There are separate template files for GO and for AR/Theory Proposals. Template files are available in several popular word-processing applications, including LaTeX and Microsoft Word.

5) Edit the template

Edit the template using your favorite word-processing application. A description of which issues need to be discussed, and guidelines for how to discuss them, are presented in HST Preparation of the PDF Attachment.

6) Create the PDF attachment.

Transform your edited template into a PDF file. Any figures in your proposal must be included into this PDF file. We will provide the reviewers with the electronic PDF files so that figures can be viewed in color. However there is no guarantee that the reviewers will view the files electronically, so please make sure your figures are useful when printed using grey scales.

7) Anonymize the PDF attachmentEnsure that your PDF attachment containing your Scientific and Technical sections are sufficiently anonymized, in accordance with the HST Anonymous Proposal Reviews guidelines.

8) Add the PDF filename path to the APT form

In your APT form, list in the appropriate box the path that points to the PDF attachment file on your local disk.

9) Review your proposal

In APT, click on ‘PDF Preview’ to get a preview of all the final information in your proposal. What you will see is the fully synthesized proposal we keep on record at STScI. The reviewers will see essentially the same, without the list of investigators and without the Team Expertise and Background sections (see HST Proposal Selection Procedures). If you are not satisfied at this stage, make any necessary changes.

You are responsible for ensuring that your PDF upload does not include extraneous material (such as extra cover pages, team expertise statements, and backup material). Extraneous material that causes the proposal to exceed the page limits or violate requirements of Dual Anonymous Peer Review will lead to disqualification of the proposal without review.

10) Institutional Endorsement

STScI does not require institutional endorsement of GO/AR Proposals in Phase I. However, some institutions do require such endorsement of all submitted proposals. It is the responsibility of each PI to follow all applicable institutional policies concerning the submission of proposals.

11) Submit your proposal 

In APT, use the Submission tool to submit your proposal to STScI. All parts are sent together (i.e., both the APT form information and the PDF attachment).

12) Receive an STScI acknowledgment of your submission

Verification of a successful submission will appear in the Submission Log on the Submission Screen in APT within about a minute. Also, the PI and all Co-Is will receive an automatic email acknowledgment that the merged PDF submission was received successfully. After the Phase I deadline has passed, and all submissions are in their final form, you will receive final notification that your submission has been successfully processed; this email will mark the completion of the submission. You should expect to receive the final notification email within 5 business days of the deadline. If there are any problems associated with your PDF attachment, you will be contacted by email.

Next: HST Filling Out the APT Phase I Proposal Form