3.2 General Observer (GO) Proposals

A GO proposal may be submitted for any amount of HST observing time, counted in terms of HST orbits. Chapter 6 of the HST Primer describes how the required number of orbits can be calculated for a particular set of observations. Programs that require fewer than 100 orbits are called Regular Programs (see Section 3.2.1), and those that require 100 or more orbits are called Large Programs (see Section 3.2.2). Programs in these categories can request observing time in future cycles when this is scientifically justified (see Section 3.2.5). The additional category of Treasury Programs (see Section 3.2.6) was started in Cycle 11 to stimulate certain types of ambitious and innovative proposals that may not naturally fit in the Regular or the Large Program categories.

Proposers are strongly encouraged to develop competitive Large and Treasury proposals.

Large and Treasury proposals will be evaluated by the TAC (see Section 6.1.2). Typically, approximately 1/3 of the available time is allocated to these types of programs; in a full cycle, this amounts to ~1000 orbits, but the allocation may be less in Cycle 16 if that cycle is truncated.

Proposers of large programs should note that all HST observations are accepted with the understanding that the timescale on which the observations will actually be obtained will depend on scheduling opportunities and demands on HST resources. Experience has shown that large programs with scheduling constraints may require execution over an extended period.

In recent cycles the acceptance rate of submitted GO Programs has been approximately independent of size. In general, proposals are either accepted or rejected in their entirety. Accordingly, you are urged to request the actual number of orbits required to achieve your science goals.

3.2.1 Regular GO Programs

Regular GO Programs are programs that request 99 orbits or less.

3.2.2 Large GO Programs

Large GO Programs are programs that request 100 orbits or more.

Large Programs should lead to a clear advance in our understanding in an important area of astronomy. They must use the unique capabilities of HST to address scientific questions in a comprehensive approach that is not possible in smaller time allocations. Selection of a Large Program for implementation does not rule out acceptance of smaller projects to do similar science, but target duplication and overall program balance will be considered.

Proposers submitting Large Programs are asked to include additional technical detail in the "Description of the Observations" section to provide information on the scheduling aspects of their program. Investigators interested in proposing Treasury/Large Programs are encouraged to consult the Treasury/Large Program User Information Report (available on the Cycle 16 Announcement Page) and the Large Program Web Page, which provide general information on how these programs are scheduled and summarize important technical and scheduling information.

Some Large Programs require substantial pipeline processing of their data to generate the final products. Examples are large mosaics for surveys, or co-additions of many exposures in deep fields. There may be situations where it would be advantageous to the PI to use the data processing infrastructures at the STScI for bulk processing of observations from a Large Program. Typically, this possibility would be explored during the budget submission process. See the Large Programs Web Page for a technical description of this opportunity.

Depending on the duration of Cycle 16, we anticipate selection of two to six programs in the 100-300 orbit range. For comparison, in Cycle 15 seven Large Programs were accepted for a total of 1209 primary orbits. Descriptions of these programs are available on the Treasury, Archival Legacy and Large (TALL) Programs Web Page.

3.2.3 Survey GO Programs

Survey Programs, introduced in the present cycle, are designed to complement Snapshot programs in providing an opportunity for statistical astronomical projects. Like other GO programs, Survey Programs are allocated a fixed number of orbits, and therefore provide guaranteed observations of a specified number of sources drawn from a larger target list. The availability of a pool of unconstrained targets is also expected to increase the overall scheduling efficiency of HST.

Survey programs have the following characteristics:

• Proposers request a specific number of orbits, corresponding to observing N targets. If the proposal is approved, the program will be allocated the requested number of orbits.
• As with Snapshot proposals, the Phase I submission requires a representative list of targets; the full target list is submitted in Phase II. Survey programs may not be used for targets of opportunity (see also Section 4.1.2).
• Proposers should submit a list of M > N targets in the Phase II stage of the proposal, where 1.5 N < M < 3N. This permits greater flexibility in scheduling observations. Survey proposals should target sources that are well distributed over a wide range of Right Ascension. Examples of programs that are not well suited to survey proposals (because they do not help improve scheduling efficiency) are surveys of targets confined to an area of a few square degrees (e.g. the LMC). or surveys confined to a few such areas (e.g. surveys of galaxies in two or three galaxy clusters). If in doubt, please consult the help desk (help@stsci.edu).
• In the case of duplications, Regular GO proposals have priority over Survey proposals, since observations of particular Survey targets are not guaranteed.
• Proposers may not assign priorities to individual targets in a survey program. Targets will be selected for execution based on available observatory resources as determined by STScI. This selection will occur as part of the normal science planning process with the other GO programs prior to the start of the observing cycle. As for all GO programs, the proposal will be deemed complete when it has exhausted the total number of orbits allocated.
• Survey proposals can request multi-orbit visits for each target.
• In order to increase scheduling efficiency, survey proposals must limit observations to less than 48 minutes per orbit (including target acquisition).
• Individual visits in a Survey proposal can be tailored in duration (number of orbits) and/or instrumental configuration for individual targets. PIs that include visits of different durations should use the Description of Observations to explain how the total orbit request was computed.
• Survey observations are not permitted to use any special scheduling constraints (e.g., CVZ, timing requirements, or telescope orientation requirements).
• Moving-target Survey Programs are acceptable only if the scheduling windows are at least one month duration. Observations of Solar system targets interior to the orbit of Mars are not permitted. Due to the amount of effort required in implementing moving target programs, these observations ordinarily cannot be revised during the observing cycle, once the initial processing has been completed.
• Survey Programs with the ACS/SBC are not allowed.
• Survey proposals cannot request time in future cycles.
• Regular Survey proposals are assessed by the review panels, in conjunction with other GO programs (see Section 6.1.1). Survey programs that request more than 100 orbits will be treated as Large Programs, and reviewed by the TAC (see Section 6.1.2).

3.2.4 Calibration GO Programs

HST is a complex observatory, with many possible combinations of observing modes and spectral elements on each instrument. Calibrations and calibration software are maintained by STScI for all of the most important and most used configurations. However, STScI does not have the resources to calibrate fully all potential capabilities of all instruments. On the other hand, the astronomical community has expressed interest in receiving support to perform calibrations for certain uncalibrated or poorly calibrated modes, or to develop specialized software for certain HST calibration and data reduction tasks. In recognition of this, STScI is encouraging outside users to submit proposals in the category of Calibration Proposals, which aims at filling in some of the gaps in our coverage of the calibration of HST and its instruments.

Calibration Proposals should not be linked explicitly to a specific science program, but should provide a calibration or calibration software that can be used by the community for existing or future programs.

Successful proposers will be required to deliver documentation, and data products and/or software to STScI to support future observing programs or archival research.

Funding is available to support Calibration Proposals in the same manner as for normal science programs. However,

Scientists affiliated with STScI are not eligible for any funding to support their role (as PI or CoI) in a Calibration Proposal.

Calibration Programs will be reviewed internally by the Instrument Division. The internal review will provide the TAC with an assessment of the feasibility of the proposal, how the proposal complements/extends the existing calibration program, and the type of science impacted by the proposed calibrations. Proposers should summarize the relevance and overall scientific utility of the calibration techniques and products described in their proposal.

Note that a specific science program that has special calibration requirements is not a Calibration Proposal; such a proposal should be submitted as a normal GO proposal and the necessary calibration observations should be added to the science program as described in Section 4.3.

Investigators interested in the submission of a Calibration Proposal are encouraged to study the Instrument Handbooks to determine the level at which STScI provides calibration and characterization, and to discuss ideas for extending these calibrations with STScI staff. Examples of the kinds of topics that have been addressed by calibration outsourcing programs of the type discussed here are:

• Calibration of faint photometric standards for ACS and WFPC2
• NICMOS polarimetric calibrations
• ACS photometric zero point verification
• Calibration of the ACS emission line filters

For a complete description of the instrument calibration plans/accuracies, and for other potential topics, please see the Scientific Instruments Web Page. Programs related to final calibration and closeout of WFPC2 are encouraged.

The data obtained for a GO Calibration Proposal will nominally be non-proprietary, as is the case for regular calibration observations. Proposers may request a proprietary period (which should be explained in the 'Special Requirements' section of the proposal; see Section 9.3), but such a request will be subject to panel and TAC review and will be granted only in exceptional circumstances if exceedingly well justified. Calibration proposals can also be submitted as Snapshot Programs (see Section 3.3.2) or Archive Programs (see Section 3.4.3). Archival Research proposals are appropriate in cases where the necessary data have already been taken, or for programs that do not require specific data but aim to develop specialized software for certain HST calibration and data reduction tasks.

All proposers are strongly encouraged to contact the appropriate instrument group to discuss their program prior to submission.

Calibration Proposals must be identified in the 'Special Proposal Types' section of the proposal (see Section 8.10).

3.2.5 Long-Term GO Programs

Regular and Large GO Programs may request HST observing time for more than one cycle.

Long-Term Programs must be limited to cases where long-baseline, multi-epoch observations are clearly required to optimize the scientific return of the project.

Long-term Programs require a long time baseline, but not necessarily a large number of HST orbits, in order to achieve their science goals. Examples include astrometric observations or long-term monitoring of variable stars or active galactic nuclei.

You may request time in as many as three observing cycles (i.e., Cycles 16, 17 and 18), but you cannot request instruments other than those presently offered in Cycle 16. Proposers should assume that WFPC2, scheduled to be replaced in SM4, will not be available in Cycles 17 and 18. Long-term proposals should describe the entire requested program and provide a cycle-by-cycle breakdown of the number of orbits requested. The scientific justification for allocating time beyond Cycle 16 should be presented in detail. For long-term programs, it is the sum of all orbits requested for Cycle 16, 17 and 18 that determines whether the program is Large or Regular.

The Cycle 16 Review Panels and TAC will be able to award limited amounts of time to Long-Term Programs for Cycles 17 and 18. GOs with approved Long-Term Programs need not submit continuation proposals in the subsequent cycles (and hence, GOs who had Cycle 16 time approved in Cycles 14 or 15 do not have to submit a Phase I continuation proposal, although a new Phase II submission will be required).

3.2.6 Treasury GO Programs

Starting in Cycle 11, the opportunities for large-scale research with HST were expanded with the introduction of the Hubble Treasury Program. This allows proposals for datasets of lasting value to the HST program that should be obtained before HST ceases operations. A Treasury Program is defined by the following characteristics:

• The project should focus on the potential to solve multiple scientific problems with a single, coherent dataset. It should enable a variety of compelling scientific investigations.
• Enhanced data products are desirable to add value to the data. Examples are reduced images, object catalogs, or collaborative observations on other facilities (for which funding can be provided). Funding for the proposed data products will depend on their timely availability, as negotiated with the STScI Director. They should be delivered to STScI in suitable digital formats for further dissemination via the HST Data Archive or related channels.
• Data taken under the Treasury Program will usually have no proprietary period (see Section 5.1), although brief proprietary periods may be requested if that will enhance the public data value.

The following additional characteristics are particularly encouraged:

• Development of new techniques for observing or data reduction.
• Creation and dissemination of tools (software, Web interfaces, models, etc.) for the scientific community to work with the data products.
• Inclusion of an Education/Public Outreach component. Note that a Phase I Treasury proposal need only summarize the planned E/PO component briefly; typically, one paragraph at the end of the Scientific Justification section. A detailed E/PO proposal should be submitted later as discussed in Chapter 11.

The emphasis in Cycle 16 remains on observations whose value is maximal if taken soon. For example, the on-orbit degradation of CCD detectors means that deep observations with ACS are of most value when obtained early in its lifetime.

Treasury Programs may request observing time to be distributed in future cycles with appropriate justification (similar to the situation for Regular and Large GO Programs; see Section 3.2.5). In addition, Treasury Programs may request observing time in future cycles if the requested number of orbits is large enough to make implementation in a single cycle impractical or impossible.

Approximately 1/3 of the available HST observing time in upcoming cycles (~1000 orbits for a full cycle, scaled appropriately for the expected duration of Cycle 16) will be available for allocation to the combination of Large Programs and Treasury Programs. As a reference, in Cycle 15 three Treasury Programs were accepted for a total of 587 primary orbits. Descriptions of all Treasury Programs are also available on the HST Treasury, Archival Legacy and Large Programs Web Page.

Selection of Treasury Programs will be handled by the TAC as part of the normal peer review process (see Section 6.1.2). Successful proposals will be reviewed by STScI to ensure observing efficiency. STScI resources may be made available to approved Treasury Programs by decision of the STScI Director. In particular, some programs require substantial pipeline processing of their data to generate the final products. Examples are large mosaics for surveys, or co-additions of many exposures in deep fields.

If scientifically justified, it is possible to propose a multi-cycle Treasury Program of order 1,000 orbits, with commensurate funding, to produce an enhanced dataset of high impact.

STScI reserves the right to conduct midterm progress reviews of Treasury Programs, to ensure that adequate progress is being made to achieve the goals of the project. Ongoing funding is contingent on the results of such reviews. For Treasury Programs above a certain cost threshold, STScI may require successful proposers to use professional project management personnel to aid the scientific team in such areas as planning, scheduling, budgeting, cost-control, and reporting.

Proposers submitting Treasury Programs are asked to include additional technical detail in the "Description of the Observations" section to provide information on the scheduling aspects of their program. Investigators interested in proposing Treasury/Large Programs are encouraged to consult the Treasury/Large Program User Information Report (available on the Cycle 16 Announcement Page) and the Large Program Web Page, which provide general information on how these programs are scheduled and summarize important technical and scheduling information.

Those interested in submitting a Treasury proposal are encouraged to read the Hubble Second Decade Committee Treasury Program Report. The report sets out the main motivations for the Treasury Program. Following the recommendation of the HST Second Decade Committee and the recent external HST TAC review (J. Toomre, chair), the Institute may organize workshops in the months before each annual TAC meeting to stimulate ideas, strategies, and collaborations for Treasury Programs. Updates on the status of Cycle 16 will be posted on the STScI home Web page, which should be visited periodically by all scientists interested in participating in Cycle 16 in any way.

Treasury Programs should be identified in the 'Special Proposal Types' section of the proposal (see Section 8.10).

The 'Scientific Justification' section of the proposal (see Section 9.1) should include a description of the scientific investigations that will be enabled by the final data products, and their importance. The 'Description of the Observations' section of the proposal (see Section 9.2) should not only describe the proposed observations and plans for data analysis, but should also describe the data products that will be made available to STScI and the community, the method of dissemination, and a realistic time line.