The Call for Proposals describes the policies and procedures for submitting a Phase I proposal for HST Observing, Archival or Theoretical Research. Please read our guide to the use of electronic document formats.
- Full Set of HST Documentation
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. Get the Primer as: PDF [US Letter Size], PDF [A4 Size], or as HTML.
Science Justification Templates for Cycle 24 HST Phase I
HST Phase I Roadmap
Up to 10% of the available HST observing time may be reserved for Director's Discretionary (DD) allocation.
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..