Pure parallel JWST observations are specified by the observer once the long range plan has been published for the new observing cycle and pure parallel observing slots are assigned. All pure parallel observations must be finalized at least 4 weeks prior to the plan window start for the primary observation.

Observing slots

The JWST calibration team has priority in the selection of available science slots needed for calibration programs. After the calibration teams select needed science slots, the remaining science slots are distributed among the accepted pure parallel programs. Scientific and technical specifications in the accepted observing proposal will determine the slots distributed to a pure parallel program. If there are multiple pure parallel proposals accepted in the cycle that have similar specifications for slots, the Program Coordination team and Planning and Scheduling team may meet to discuss the distribution of slots. After the distribution of slots has been decided, the available slots will be assigned to pure parallel programs. 

Specify observations in APT

Pure parallel observations are crafted by the observer based on their example observations and sized to fit the pure parallel slots assigned to them. Each slot corresponds to a single exposure (i.e., a single dither position). Currently only the following 5 templates can be proposed for science pure parallel observing: MIRI imaging, NIRCam imaging, NIRCam WFSS, NIRISS imaging and NIRISS WFSS. There are no options for dithering in the observing templates. There can only be one exposure specification in a pure parallel observation, EXPOSURES/DITHER must be set to 1, and no special requirements may be specified for a science pure parallel observation. 

More details for specifying observations can be found at https://jwst-docs.stsci.edu/jppom/parallel-observations/pure-parallel-observations.  

Making changes

Pure parallel observations may be changed after their initial specification, as follows:

1. Go to https://parallels.stsci.edu/
2. Select the cycle your program was accepted
3. Go to the pure parallel observation(s) you need to make changes to
4. Look at the start time in the column labeled "Plan Windows" for the matched prime visit(s)
5. Major changes must be made at least 4 weeks prior to the start of the plan window of the primary visit.
6. If for any reason you miss the 4 week mark to make changes, please consult with your PC on the changes needed and they will let you know if any last minute changes are possible.  

The above timeline is for major changes. Problems that need to be fixed following PC review are considered minor changes (e.g., reduction in exposure times). Minor changes can be made in less than 4 weeks as the reviews take less time to complete. However, updates should be made as soon as possible just in case the prime visit(s) get moved earlier than planned for scheduling.