Coordinated and Pure-Parallel Observations

Parallel observing refers to simultaneously operating more than a single science instrument (limited to two instruments for Cycle 1).  For JWST proposals, there will be two basic modes of parallel operations: coordinated parallels and pure parallels. Further information with examples, roadmaps, and templates are provided on JWST Parallel Observations. Related policy can be found on JWST Science Parallel Observation Policies and Guidelines

Coordinated science parallel observations are those in which simultaneous observations may be made with instruments other than the primary instrument. Coordinated science parallel observations must have science goals that support or complement the prime science programs, and must be explicitly justified in the proposal. In Cycle 1, the following coordinated parallel modes will be supported:

  1. NIRCam Imaging and MIRI Imaging,

  2. NIRCam imaging and NIRISS Wide-Field Slitless Spectroscopy (WFSS), 

  3. NIRCam imaging and NIRISS Imaging (NIRCam must be the prime instrument),

  4. NIRCam imaging and NIRSpec MOS (NIRSpec must be the prime instrument),

  5. MIRI imaging and NIRISS WFSS,

  6. NIRCam WFSS and MIRI Imaging (NIRCam must be the prime instrument),
  7. NIRCam WFSS and NIRISS Imaging (NIRCam must be the prime instrument),
  8. NIRSpec MOS and MIRI Imaging (NIRSpec must be prime instrument).  

Only direct imaging with standard narrow, medium, or broad band filters is allowed for NIRCam and MIRI observations in these coordinated parallel modes. Additional instrument combinations may be available in future cycles. 

Pure-parallel observations utilize instruments other than the primary instrument on observations from unrelated proposals. Unlike coordinated parallels, pure parallel observations are proposed as entirely separate programs of investigation.  Pure parallels use parallel observing slots created by observations of programs that do not use coordinated parallels. Pure parallel observations will not be allowed to influence the dither patterns or other aspects of the observing strategy of the primary observations to which they are attached, since the primary observations will belong to entirely separate science proposals. 

Pure-parallel programs may propose for observations with NIRCam imaging, NIRISS imaging and WFSS, and MIRI imaging (NIRSpec is not allowed as the parallel instrument). For accepted programs, the observations will be paired with suitable prime observations by GO, GTO and ERS programs. A number of prime templates cannot have pure parallels attached to them, including MIRI Coronagraphic Imaging, NIRCam Coronagraphic Imaging, NIRCam Time Series, NIRCam Grism Time Series, NIRISS Single Object Slitless Spectroscopy, NIRISS Aperture Masking Interferometry, and NIRSpec Bright Object Time Series. Please check JWST Parallel Observations for the full list of template combinations that are allowed and expected to be available for use in Cycle 1. We anticipate that pure parallel opportunities with durations from ~100 seconds to several thousand seconds will be available; the number of such opportunities will not be known until the Cycle 1 GO program is selected. Note that observatory activities such as calibration observations for the instruments will take priority in the assignment of available pure parallel slots.

Next: Time Constrained Observations