STScI Logo

Hubble Space Telescope

Phase II Proposal Instructions

During Phase II, General Observers (GOs) with accepted proposals, must provide complete details of their proposed observations so that STScI can conduct a full technical feasibility review. The Phase II information will then be used to schedule the actual observations and obtain data.

The Phase II Proposal Instructions, has the following purposes:
* To describe the information that must be submitted to STScI by GOs during Phase II.
* To describe what you have to provide in APT (Astronomer’s Proposal Tool).
* To show how to submit the information to STScI.

Proposers should be familiar with the Cycle 26 Call for Proposals, and with the Instrument Handbooks.


The Phase II Proposal Instructions are available on our Hubble Space Telescope User Documentation (HDOX) site at: Phase II Instructions.

Release Documents

    The Call for Proposals describes the policies and procedures for submitting a HST Phase I proposal. Go to the CP.

    The Primer provides an introductory overview of the Hubble Space Telescope and explains how to calculate the appropriate number of orbits for an observing proposal. Go to the Primer.

    Science Justification Templates for Cycle 26 HST Phase I

  • Full Set of HST Documentation

HST Phase I Roadmap

    The Roadmap is a step-by-step guide to proposing and submitting an HST proposal. Download APT here.

DD Time

Up to 10% of the available HST observing time may be reserved for Director's Discretionary (DD) allocation.

Mid-Cycle Proposals

Up to 200 orbits per cycle will be available for Mid-Cycle GO programs. Mid-Cycle programs were initiated in Cycle 23 to provide the community with an opportunity to propose for in-cycle observations of recently-discovered, non-variable objects. As such, they complement Director’s Discretionary programs, which target unexpected transient phenomena and time-critical observations..

Special Programs from Past Cycles

Status of Current and Past Programs:

Past Proposal Opportunities