HST Cycle 33 proposers are encouraged to follow this checklist for writing and submitting proposals for the Hubble Space Telescope (HST).

 Know the deadlines

The Cycle 33 Phase I proposal deadline is Thursday, April 10, 2025 at 8:00pm EDT.

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

HST Phase I Proposal Roadmap

 Know where to find the HST User Documentation

• HST User Documentation
• HST Proposal Opportunities and Science Policies
• HST Observatory and Instrumentation Documentation
  • The Hubble Space Telescope Primer for Cycle 33
  • Advanced Camera for Surveys
  • Cosmic Origins Spectrograph
  • Space Telescope Imaging Spectrograph
  • Wide Field Camera 3
  • Fine Guidance Sensor

 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 a 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 or targets  
• 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 Technical Justification.  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.  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 72 hours of the deadline, please submit an incident to the HST Help Desk, https://hsthelp.stsci.edu/, as your submission was NOT RECEIVED and the 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 Telescope Allocation Committee 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.

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

Next: HST Anonymous Proposal Reviews