JWST Cycle 1 Special Submission Requirements

Some observation types may require special accommodations for full specification in the Astronomers Proposal Tool.

There are known limitations in submitting observations using some observing modes through APT. Those special submission requirements are described here. Most updates to planning guides, or more specific submission tips, will be posted as articles in the JWST Help Desk, particularly in the Knowledge Base

Mosaic observations

Proposers are required to submit complete APT files of programs requesting mosaics by the proposal deadline, as this is the only way to estimate the total time requested. In addition, complex programs like large mosaics that involve timing constraints impose significant restrictions on the Long Range Plan and therefore need to be incorporated into the schedule as early as possible. Proposers should be aware that:

1. The Guide Star Catalog used by APT at the time of the release of this Call may be insufficient to find guide stars for all the mosaic tiles at the same time. In those cases, when running the program through the Visit Planner in APT, warnings are triggered and the mosaic tiles cannot be scheduled simultaneously. If guide stars are not available for all the tiles at the same orientation, proposers should refer to the mosaic documentation for guidelines on how to proceed (see for example documentation discussing mosaic planning and tile splitting). Please note that it is important to resolve  as many as possible of these scheduling warnings before submission because otherwise smart accounting will not work and APT will assume each tile is a separate observation, each requiring a major slew, greatly overestimating the requested time.

2.  If  tile splitting is required for scheduling purposes, proposers are recommended to set the Position Angle at a value that allows the largest number of tiles to be scheduled simultaneously. Proposers should be aware that a fixed position angle imposes constraints on scheduling observations in the Long Range Plan. Consequently, if the proposal is accepted, STScI may adjust the Position Angle of the mosaic to minimize disruptions to the schedule. If a specific Position Angle is necessary to achieve the science objectives, this should be clearly indicated in the PDF of the proposal. Proposers are discouraged to request this unless necessary to achieve science objectives.

3.  Proposers should bear in mind that if tile splitting is necessary, observations of problematic tiles will be made at a different Position Angle from the majority of the mosaic. This may create gaps in the coverage. If the science goals require full coverage, the proposer should indicate this clearly in the PDF of the proposal because it may require adjusting the size and/or dithering pattern of the tiles that need to be scheduled separately.

STScI staff will work with proposers to resolve, as far as possible, any outstanding issues and optimize the observing efficiency for accepted proposals.

NIRSpec MOS observations

The target selection process for NIRSpec MOS observations must take account of how objects are projected onto the micro-shutter array, and therefore depends on the orientation of the observations and the optical distortions present along the NIRSpec optical path.   In general, to ensure program schedulability, NIRSpec MOS science observations should be submitted with no orient constraint in proposals. We recommend that proposers who wish to constrain their observation orient define a preferred orientation within a range of no less than 30o (or ±15o), with an appropriate scientific justification. The exact execution orientation for any observation will not be determined until that observation is placed on the Long Range Plan (LRP) for Cycle 1.  As a result, NIRSpec MOS observations cannot be fully specified at the time of submission. Proposers must submit in their proposals an associated source list for the final target assignment within any given pointing (see JWST Cycle 1 Observation Mode Restrictions). Once the orientation has been defined for successful proposals, the proposer will be informed and can select the individual targets for MOS observation. A full description of the NIRSpec MOS APT submission process is given in the NIRSpec MOS JDox pages.

Coronagraphic observations

Proposers should be aware that:

  1. The PSF calibrator star that must be fully specified in the proposals might be changed prior to executing an accepted program if both the proposer and STScI agree that this change is beneficial to the science yield of the program, under the condition that the science goals are unaffected and requested time is not increased.
  2. The overheads associated with a given observation depend on the exact observing sequence and the ordering of the exposures. Proposers should make their best effort to optimize the program by minimizing overheads following the guidelines in the High Contrast Imaging documentation. As with all GO proposals, if the proposal is accepted, the Instrument Scientist may also suggest changes to achieve this goal. 

Background limited observations

By requirement, the JWST Science & Operations Center (S&OC) will schedule background-limited observations when the Zodiacal background for each target is relatively low. Users may indicate that observations are background-limited by using the Background special requirement in APT.  The JWST Background-Limited Observations page provides a method to to determine whether an observation is background-limited, and advice on whether to opt in to the Background special requirement. Proposers should be aware that the background special requirement is effectively a scheduling constraint, and as such may conflict with other user-applied scheduling constraints.

Overhead override requests

Proposers should be aware that in rare cases there may be inaccuracies in the total charged duration reported in their APT submission. Known issues will be described in APT User Documentation; proposers should check that site for updates until the time of submission, as well as the Late Breaking News section of the Call.  In some cases, specific guidelines will be given with regard to adjusting the charged duration reported by APT; in those cases, the proposer should report and justify their corrected charged duration in the PDF of the proposal. For overhead inaccuracies not covered by the guidelines, please contact the JWST Help Desk. All overhead override requests will be subject to a review by STScI. 

Next: JWST Cycle 1 Observation Mode Restrictions

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