HST Cycle 34 proposers are encouraged to follow this checklist for writing and submitting proposals for the Hubble Space Telescope (HST).

 Know the deadlines

The Cycle 34 Phase I proposal deadline is Thursday, April 16, 2026 at 8:00pm EDT.

Director's Discretionary Time proposals can be submitted at any time.

 Know where to find the HST User Documentation

• HST User Documentation is the top level page containing HST documentation for users.
• HST Proposal Opportunities and Science Policies is the top level page with information about HST proposals and STScI science policy (including the Call for Proposals and Primer).
• HST Phase I Proposal Roadmap has guidelines for how to prepare and submit your HST Phase I proposal.
• HST Observatory and Instrumentation Documentation
  • The Hubble Space Telescope Primer is the top level page for the HST Cycle 34 Primer, which contains information about the current status of HST and its instruments.
  • Advanced Camera for Surveys Instrument Handbook
  • Cosmic Origins Spectrograph Instrument Handbook
  • Space Telescope Imaging Spectrograph Instrument Handbook
  • Wide Field Camera 3 Instrument Handbook
  • Fine Guidance Sensor Instrument Handbook

 Learn the HST observation planning tools

• Proposers should assume nominal performance from HST, as described in the HST User Documentation, and as assumed by the HST Exposure Time Calculator (ETC).
   
• HST Exposure Time Calculator (ETC) – The HST ETC is a web-based tool for estimating how much exposure (science) time will be required for different HST instrument modes and configurations to achieve the desired science goals.
  
  
• Astronomer's Proposal Tool (APT) –  APT is a stand-alone software package required for preparing HST observations and submitting HST proposals. Download APT here.

 Design an HST observing program in APT

• Download and install the latest version of APT. 
• Create a New HST proposal in APT and fill out the Proposal Information section
• Enter your target(s)
• Create a new Observation Folder and a new Observation with an observation template. 
• View an Observation with the Aladin visualizer tool. 
• Resolve any errors or warnings in APT.

• Check for duplicate observations in the archive and with the list of approved observations.

 Write your science proposal

Create the PDF attachment of the proposal narrative, which includes a number of required text sections such as the Scientific Justification, and Description of Observations (GO) or Analysis Plan (AR). Note that any special requirements (orient constraints, timing constraints, linking visits, etc.) MUST be specified in the Special Requirements section of the proposal AND flagged in APT. Failure to do so could result in disqualification of the proposal or termination of the program. See the documentation for the Special Requirements section of the proposal and flags in APT for more details.

 Submit your HST proposal

• Attach the PDF of your scientific proposal to the APT program on Proposal Information form.
• Preview the entire proposal by selecting the APT PDF Preview tool. This view will merge the information provided in APT along with the PDF attachment, and is what the Telescope Allocation Committee (TAC) will review. 
• Submit your completed proposal with APT. Select the APT Submission Tool in the top tool bar and follow the instructions.  In the Submission Log window you will see a message giving the time of the submission, the assigned proposal ID (if a new proposal), and the submission status.
• After the initial submission, proposals can be re-submitted as needed (up to the stated deadline). Resubmitting does not change the proposal number received upon the initial submission.

 Wait and Check

After you submit your proposal, all investigators will receive an automatic email acknowledgment that the submission was received successfully. If you do not receive that email within minutes of your submission, please check the APT Submission Log Window for a problem. In addition, all investigators will receive an additional email indicating whether your proposal was successfully processed after the submission deadline. If you do not receive this acknowledgement within 5 business days of the deadline, please submit an incident to the HST Help Desk, https://hsthelp.stsci.edu/, as your submission was NOT RECEIVED and the Telescope Allocation Committee (TAC) WILL NOT see your proposal; please provide the submission ID information from the APT Submission Log window. If there are any problems associated with your PDF attachment or APT information submitted, you will be contacted by email separately.

Notification of your proposal's status (approved or rejected) generally occurs within ~3 weeks of the TAC meeting. 

 Next steps for approved programs

Selected Phase I programs are contingent on the approval of the Phase II proposal. The HST Phase II Proposal Roadmap provides an overview and further details of the Phase II process.

Successful HST observing proposals will be reviewed by a STScI instrument scientist and program coordinator. Programs may require adjustments or revisions after the award. The Instrument Scientist and Program Coordinator will iterate with proposers to finalize the observations in accordance with the TAC recommendations, under the approval of the STScI Director.

U.S. investigators with approved HST programs are eligible for funding. See HST Grant Funding and Budget Submissions for further details. 

Next: HST Anonymous Proposal Reviews