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Hubble Space Telescope Call for Proposals for Cycle 22 > Chapter 3: Proposal Categories > 3.3 Snapshot (SNAP) Proposals

3.3 Snapshot (SNAP) Proposals
Snapshot (SNAP) Programs consist of separate, relatively short observations with typical durations of 45 minutes or less (including all overheads). During the process of optimizing the HST observing schedule, the scheduling algorithm occasionally finds short time intervals where it is impossible to schedule any exposures from the pool of accepted GO Programs. In order to make the HST schedule more efficient, STScI has developed the capability to insert Snapshot exposures of objects selected from a large list of available candidates. In Cycle 22, up to 1000 SNAP observations may be accepted to provide a sufficiently large pool of candidates.
3.3.1 Characteristics of SNAPs
Accepted SNAP Programs are allocated a specific number of targets. However, there is no guarantee that any individual target will be observed, because SNAPs are placed on the schedule only after the observing sequence has been determined for the higher-priority GO targets. The number of observations actually executed depends on the availability of appropriate schedule gaps. In general, only a fraction of the allocated targets will be observed. Unlike GO Programs (see Section 3.2.5), SNAP Programs cannot request observing time in future cycles. However, un-executed SNAPs remain active at decreased priority for a second cycle.
There is no commitment on the part of STScI to obtain any specific completion factor for SNAP Programs.
The average expected completion rate for SNAP Programs is ~33%. However, the actual completion rates for individual programs vary, depending on several factors including the number of targets and the average duration and sky distribution of the observations. In general, shorter-duration and well-distributed SNAP observations have a higher number of scheduling opportunities and a higher chance of being executed than longer duration and/or spatially clustered SNAP observations.
Investigators interested in proposing for SNAPs are encouraged to consult the SNAP User Information Report, which contains details on how SNAPs are scheduled, the rules pertaining to them, and other useful information.
3.3.2 Calibration SNAP Proposals
Calibration Proposals (see Section 3.2.4) may also be submitted as SNAP Proposals. As with GO Calibration Programs, all data obtained will be non-proprietary unless proposers specifically request a proprietary period. Successful proposers will be required to deliver documentation, and data products and/or software to STScI to support future observing or archival programs.
Users submitting Calibration Proposals are required to contact the appropriate instrument group to discuss their program prior to submission.
3.3.3 Guidelines for SNAP Proposals
Please consider the following when developing your SNAP Proposal:
You need not give a complete list of all targets and their coordinates in your Phase I proposal. However, you must specify the number of targets, and unambiguously identify the targets (e.g., reference to target lists in papers, or give a detailed description of the target characteristics). SNAP exposures may not be used for targets of opportunity (see also Section 4.1.2).
In the ‘Observation Summary’ section of the proposal (see Section 8.16) you should provide a typical example of a SNAP exposure.

Hubble Space Telescope Call for Proposals for Cycle 22 > Chapter 3: Proposal Categories > 3.3 Snapshot (SNAP) Proposals

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