JWST Conventions

Association Naming

When produced through the ground processing, all association files are named according to the following scheme:



  • jw: All JWST-related products begin with jw

  • PPPPP: 5 digit proposal number

  • TNNNN: Candidate Identifier. Can be one of the following:

    • oNNN: Observation candidate specified by the letter o followed by a 3 digit number.

    • c1NNN: Association candidate, specified by the letter ‘c’, followed by a number starting at 1001.

    • a3NNN: Discovered whole program associations, specified by the letter ‘a’, followed by a number starting at 3001

    • rNNNN: Reserved for future use. If you see this in practice, file an issue to have this document updated.

  • YYYYMMDDtHHMMSS: This is generically referred to as the version_id. DMS specifies this as a timestamp. Note: When used outside the workflow, this field is user-specifiable.

  • ATYPE: The type of association. See Association Types

  • MMMMM: A counter for each type of association created.

Association Types

Each association is intended to make a specific science product. The type of science product is indicated by the ATYPE field in the association file name (see Association Naming), and in the asn_type meta keyword of the association itself (see Association Meta Keywords).

The pipeline uses this type as the key to indicate which Level 2 or Level 3 pipeline module to use to process this association.

The current association types are:

Field Guide to File Names

The high-level distinctions between stage 2, stage 3, exposure-centric, and target-centric files can be determined by the following file patterns. These patterns are not intended to fully define all the specific types of files there are. However, these are the main classifications, from which the documentation for the individual calibrations steps and pipelines will describe any further details.

The most general regex matches all files that have been produced by Stage 3 processing:


The following regexes differentiate between exposure-centric and target-centric files.

  • Files containing exposure-centric data

    The following regex matches files names produced by either Stage 2 or 3 calibration and containing exposure-centric data:

  • Files containing target-centric data

    The following regex matches file names produced by Stage 3 calibration and containing target-centric data: