The Hubble Space Telescope Primer for Cycle 27

The HST Primer provides an introduction to the Hubble Space Telescope for Phase I proposers

About This Document

The Hubble Space Telescope (HST) Primer for Cycle 27 is a companion document to the Hubble Space Telescope Call for Proposals for Cycle 27. It provides an overview of HST, with basic information about telescope operations, instrument capabilities, and technical aspects of the proposal preparation process. A thorough understanding of the material in this document is essential for the preparation of a competitive proposal. The Call for Proposals discusses the policies and procedures for submitting a Phase I proposal for HST observing or archival research. Technical documentation on the instruments are available in their respective handbooks, available on the HST Document overview site.

Late Breaking News


  • Two important reminders:
    • Proposers are reminded that the HST proposal review follows a Dual Anonymous system, and proposals must conform with the guidelines presented in the Call for Proposals. Reviewers are asked to flag non-compliant proposals, and excessive violations can (and have) resulted in proposals being disqualified from consideration. Proposers will receive a limited number of warnings for minor infringements.
    • All proposers must indicate whether any of their observations will require orientation constraints. Detailed orientations need not be specified at this time, but the specific observations affected must be identified, with an appropriate justification, in the “Special Requirements” section of the proposal. As endorsed by the STUC, the goal is to minimize unnecessary scheduling constraints on HST observations. Proposers who fail to identify and justify orientation constraints in the Phase I proposal will generally require approval by the TTRB to add any constraints in Phase II.


  • Joint Program proposers do not need to specify whether they were recently awarded time for similar or related observations with the coordinating facility. The HST Cycle 27 Preparation of the PDF Attachment instructions have been updated.

See also HST Cycle 27 New and Important Features

Proposing Calendar and Deadlines

  • Phase I proposal deadline: April 5, 2019 at 8:00pm EDT

  • Cycle 27 Peer Review: June 2019

  • Phase II proposal deadline: July 25, 2019

  • Budget deadline: August 8, 2019

  • Cycle 27 Mid-Cycle Deadline: September 27, 2019

Where to Get Help

Submit questions to the HST Help Desk at See for additional tools and resources.

Who's Responsible

The HST Call for Proposals and related materials for Cycle 27 were edited by Louis-Gregory Strolger. The Associate Directory for Science, Neill Reid, and the Science Mission Office at STScI are responsible for the oversight of the HST science program selection process, whose members include Alessandra Aloisi (Head of Science Mission Office), Claus Leitherer (Head of Science Policies Group), Katey Alatalo, Christine Chen, Andrew Fruchter, Amaya Moro-Martin, Molly Peeples, Louis-Gregory Strolger, and Technical Manager Brett Blacker.

Next: HST Cycle 27 Primer Resources, Tools, and Other Documentation

The Hubble Space Telescope Primer for Cycle 27

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HST Proposal Opportunities and Science Policies

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