HST proposals that request observations which duplicate planned or existing JWST observations are identified and adjudicated according to STScI/NASA policy. Duplications will be adjudicated on a case by case basis, taking into account factors such as data access and the overall depth of observation. In the absence of other factors, priority will generally be given to observations that maximize the potential science. 

Introduction

Duplicate observations may be permitted if they are scientifically justified; in general, duplications in General Observer (GO) programs must be recommended for execution by the Telescope Allocation Committee. 

Special policies apply to cases in which a proposed observation with the Hubble Telescope would duplicate another observation either already obtained or scheduled to be obtained. The prime purpose is to maximize the scientific return from HST by making the most efficient use of the available observing time through minimizing scientifically-unjustified repeat observations. The goal is not to protect specific scientific programs: as with other NASA Great Observatories, HST will execute observing programs that address the same science goals through different observation techniques if those programs are recommended for approval through the review process and approved by the STScI Director.

Definition of a duplicate observation

An observation is a duplication of another observation if it is on the same astronomical source or field, with the same instrument in the same hardware mode (i.e. generally using the same Astronomer’s Proposal Tool template), with similar sensitivity and similar spectral range. It is the responsibility of observers to check their proposed observations against the catalog of previously executed or accepted observations and provide a suitable justification for any duplication.

Single source observations  

Single source observations are defined as including coronagraphy and spectroscopy with the Space Telescope Imaging Spectrograph (STIS) or the Cosmic Origins Spectrograph (COS). A duplication is an observation of the same source with the same instrument configuration and an exposure time within a factor of ~4; for present purposes, “exposure time” is defined as the total photon collection duration given by the Astronomer’s Proposal Tool. Spectroscopic observations of an individual source are flagged as potential duplications if there is major overlap (>50%) in the spectral range with previous observations of the same source.

Areal Observations

Areal observations are defined as including direct imaging and wide-field slitless spectroscopy with Wide-Field Camera 3 (WFC3), the Advanced Camera for Surveys (ACS) or STIS. Observations are identified as potential duplications if they are taken with the same instrument configuration and with an exposure time within a factor of 4, and if the telescope pointing results in major overlap (>50%) of the Field of View.

Duplication policy

Proposed observations that meet the criteria outlined above are potential duplications and should be identified as such by the proposer. Any such observations must be justified in the appropriate section of the proposal. Duplicate observations are permitted if they are scientifically justified: examples might include repeat observations of intrinsically variable objects, or duplicate imaging observations made over a time baseline to determine astrometric motions. Duplications are generally subject to review by the Telescope Allocation Committee (TAC) and require approval by the STScI Director. Duplications that are identified after the TAC are assessed by the Science Policies Group, who may ask for feedback from the TAC. The STScI Director has the final

Duplications are adjudicated on a case by case basis, taking into account factors such as data access and the overall depth of observation. In the absence of other factors, priority will generally be given to observations that maximize the potential science. 

Any unjustified duplications of previously executed or accepted observations that come to the attention of the peer reviewers and/or STScI could lead to rejection during or after the TAC deliberations. Without an explicit TAC recommendation to retain duplicating exposures, unjustified duplications discovered in an approved GO program can be disallowed. In such cases, no compensatory observing time will be allowed for GO programs and the associated observing time will be removed from the allocation.

Regular GO programs will have their orbit allocation reduced if genuine duplications are found. Principal Investigators may not propose alternative targets for disallowed observations. The TAC approves observations of a specific set of targets to achieve the science goals of a program; if a target is removed through duplication with another program, the PI will have access to the appropriate data for that target after the exclusive access period expires.

SNAP programs are allowed to substitute similar targets if duplications are found, provided the new targets match the original target selection criteria. Only a subset of SNAP targets are observed, and there is no guarantee that any particular target will be scheduled in the cycle.

Parallels are not considered in terms of duplications, so a prime observation will not be disallowed even if an accompanying parallel observation duplicates an existing observation.

How to Check for Duplications

To check for duplications with past programs, PIs should use the tools and links on the HST Proposal Support webpage at MAST. The following two options are available:

• The HST Duplication Checking Web Form
• The Planned and Archived Exposures Catalog (PAEC), which is available from the HST Catalogs webpage at MAST. This catalog contains summary information about exposures in ASCII format and can be browsed with any text editor. It is normally updated monthly, but will be kept fixed between the release of this Call for Proposals and the Phase I deadline.

PIs should ensure that they either search in the HST duplication table (automatic if you use the Duplication Checking Web Form) or the PAEC. Other archive tables, such as the science table or the ASCII format Archived Exposures Catalog (AEC) do not include exposures that have been approved but have not yet executed, and are therefore not suitable for a complete duplication check.

Adjudication

Duplications are adjudicated on a case by case basis, taking into account factors such as data access and the overall depth of observation. In the absence of other factors, priority will generally be given to observations that maximize the potential science.

Duplications are generally subject to review by the Telescope Allocation Committee (TAC) and require approval by the STScI Director. The TAC will review the justification presented in proposals for observations that duplicate those from past programs. In addition, they will adjudicate same-cycle programs that are identified prior to or during the TAC meeting.

Duplications that are identified after the TAC are assessed by the Science Policies Group (SPG). If the duplication is with a past program and the proposal lacks any justification, then the new observation will be disallowed. If the duplication is between in-cycle programs, SPG may ask for feedback from the TAC before making a recommendation to the STScI Director, who has the final decision.

Embargoed observations

Under exceptional circumstances, duplicate observations may be held in embargo for a short period. Any such decisions will require formal approval by the STScI Director.