Proposal Types, Sizes and Science Areas

More information about everything on this page can be found in the Call for Proposals, and relevant links are provided throughout. Here we give a high level summary.

HST proposals may request both observing time and funding (proposers from U.S. institutions only). There are three main types.

General Observer (GO)

General Observer proposals request observing time in orbits. GO proposals are classified by size:

  • Small (1-34 orbits), of which we will refer to a subset as Very Small (1-15 orbits).
  • Medium (>34-74 orbits)
  • Large (>74 orbits).

US-based investigators on successful proposals are awarded funding to carry out the data reduction and analysis.

GO are flagged as Joint Observing Programs if they require Chandra, TESS, NOIRLab, NRAO, or XMM time to complete their science goals, a Calibration proposal if the observations will lead to an improved calibration of the facility for the community, a Treasury proposal if the proposal addresses multiple science questions and the team plans to provide high level science products, or a Long-Term Status Proposal if the observations are spread over Cycle 30 and subsequent cycles. GO-Archival programs are GO programs that also have a significant Archival research component.

Snapshot (SNAP)

Snapshot programs use small amounts of otherwise idle observing time in the HST schedule; they are allocated a number of targets of which in practice only a fraction, ~30 - 70%, will actually be observed. US-based investigators on successful proposals are awarded funding to carry out the data reduction and analysis.

Typically, only one third of the proposed targets are likely to be observed and exactly which of the targets is not known. The science case should be made with these facts in mind, that is, the science should be possible with around one-third of the targets and should not depend on any particular target or subset of targets.

Archival Research (AR)

Archival programs are to carry out investigations using HST data from the Mikulski Archive for Space Telescopes (MAST) or to do theoretical work to benefit HST science (AR Theory). US-based investigators on successful proposals are awarded funding ONLY to carry out their proposed program. Reviewers will not be asked to recommend or judge the amount of funding, but they are asked to assess whether the proposal requests sufficient resources to achieve the science goals.

A subset of AR proposals are Theory proposals, which propose theoretical and computational work to support HST science. Be aware that, despite being classed as AR proposals, these proposals will use little or no archival data.

Calibration AR proposals support analysis of Calibration data that will already be available in Cycle 31. Finally, Cloud Computation Studies will take advantage of the availability of HST data on Amazon Web Services (AWS) for large-scale data analyses.

Science Areas

Proposals are assigned to eight science areas:

  1. Solar System Astronomy,
  2. Exoplanets and Exoplanet Formation,
  3. Stellar Physics and Stellar Types,
  4. Stellar Populations and the Interstellar Medium,
  5. Galaxies,
  6. Intergalactic Medium and Circumgalactic Medium,
  7. Supermassive Black Holes and Active Galaxies,
  8. Large-Scale Structure of the Universe.

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