JWST allows two different types of parallel observations - Coordinated and Pure - and this article contains the descriptions of those types.
Parallel science uses two or more Science Instruments at the same time. The Primary observation determines the pointing of JWST and always takes precedence. The Parallel observation is enabled because the primary observation provides suitable conditions.
- Coordinated parallels are written to be part of the same proposal, with the intention of scheduling the primary and the parallels together. Coordinated parallels are inextricably linked with their primaries: both must be scheduled in order for either to be scheduled.
- Pure parallel slots are defined at the beginning of the observing cycle based on available primary visits. The pure parallel observations are crafted to match these slots and are scheduled simultaneously with and according to the plan windows of those primary visits. Pure parallels may not affect the scheduling of primary visits. Pure parallel observations are always in a different proposal from the prime observations.
More about Parallel Observations