HST Cycle 29 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 April 9, 2021 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 Cycle 28 Filling Out the APT Proposal Form We strongly recommend that proposers start preparing their proposals early in order to give themselves enough time to learn APT. Cycle 29 will use APT 2020.5, released on December 18, 2020.

Please 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 29 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. 

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

Page Limit for the text of the Scientific Justification 

Small GO83

Medium GO



Large GO



Treasury GO



Regular AR83
Calibration AR83
Theory AR83

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; pages beyond the specified limits will be removed and will not be available to reviewers.
  • 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.
  • 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.

Proposal Preparation Checklist

Table: Proposal Preparation Checklist 



1) Review the Phase I Roadmap

The HST Cycle 29 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 Cycle 28 Filling Out the APT 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 Cycle 29 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 Cycle 29 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 Cycle 29 Proposal Selection Procedures). If you are not satisfied at this stage, make any necessary changes.

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. If you do not receive the final notification email within 72 hours of the deadline, please contact the STScI Help Desk and provide the submission ID from the APT Submission Log window. If there are any problems associated with your PDF attachment, you will be contacted by email.

Next: HST Cycle 28 Filling Out the APT Proposal Form