Users are responsible for checking for duplicate or potentially duplicate observations, and explaining any such observations in their proposals.
In the interest of maximizing the science return of JWST, any proposed observations that duplicate existing or planned observations must be scientifically justified by the proposer. Defining exactly what constitutes a duplication can be complicated in some cases, but in general, it includes some combination of a) same source or field; b) same or similar instrument; c) same mode or template; d) similar (within a defined factor) exposure time or Signal-to-noise ratio; and e) for spectral modes, similar spectral resolution and/or significantly overlapping spectral coverage.
Duplication checking prior to submission is the user's responsibility. Any duplications or potential duplications (for programs where the details are not known up front) must be discussed and/or justified in the text of the proposal. Failure to do so may result in the rejection of the proposed observation even after proposal acceptance. For accepted proposals, STScI will perform a detailed duplication check as well.
See also: JWST Duplication policy
To avoid unintentional duplications, proposers will be required to check their proposed observations against those already approved (or actually observed in future cycles). When valid JWST observations have been obtained and archived, users will be able to go to the Mikulski Archive for Space Telescopes (MAST) and use the available tools to ensure their proposed targets are not duplicating existing or planned JWST observations. For Cycle 1 General Observers, there are of course no existing observations, but Guaranteed Time Observers (GTOs) and Early Release Science (ERS) proposals will have been accepted prior to Cycle 1. The JWST Project will make the relevant materials available to the community by the time of the JWST Cycle 1 Call for Proposals. Note that targets will not be protected, but rather observations with a particular instrument and instrument mode of targets are protected against unjustified duplications. Many users will want to do this duplication checking step prior to going to the effort of entering and validating an APT proposal, to avoid the potential of only finding out after the fact that duplications have been proposed.
In addition to the above, a tool is being developed within APT that will allow users to check a complete or nearly complete program against the MAST archive information. When this tool is available the user will select one or more observations in your APT proposal and click the Duplications tool in the top APT tool bar. This will open a separate browser window with an interface to MAST. Any potential duplications found by the MAST search will be displayed for the user to use in assessing whether the selected observation(s) are potential duplications. The availability and timing of the release of this tool in APT is currently under discussion.
Once a proposal is accepted, one of this first steps in proposal processing is a duplication check performed by STScI personnel. The STScI software not only checks for duplications against previous and planned observations, but also checks within the ensemble of accepted programs for a given cycle to catch any potential duplications. STScI personnel will contact affected PIs to resolve any such duplications if they occur. Any duplications found against previous or planned observations that were not revealed by the PI and explicitly approved by the TAC and STScI director may be disallowed and the program's resource allocation decreased accordingly.
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