Information about what's new in the latest JWST pipeline build, and what was done in previous builds, is provided in this article. It also gives a preview of some updates likely to be coming soon in upcoming builds. The information contained here is generally a high-level summary of changes, with links provided to more extensive external documentation. 

Build lifecycle

JWST pipeline development proceeds according to a quarterly build schedule. Each quarter, the active development version of the JWST Science Calibration Pipeline is frozen, combined with other dependent software (e.g., the JWST Science Data Processing system; SDP) and a particular CRDS reference file context, and tagged to produce a candidate build. This candidate build is then tested extensively prior to becoming an operations build installed by the Data Management System (DMS) at STScI and used to reprocess all previous JWST data as well as newly obtained observations. Once a build is no longer operational, it becomes archived.

There are thus four kinds of builds:

• Development (Dev) build:  Changing daily, uses the Latest CRDS context, not recommended for non-developers.
• Candidate build: Development has finished, currently working on testing and documentation. Uses a fixed CRDS context. Available for experienced users.
• Operations build: Installed at STScI and being used to produce data products available in MAST. Uses a fixed CRDS context. Default recommendation for users.
• Archived build: Outdated operations build that is no longer recommended for general use (may still correspond to some MAST data products until reprocessing is completed).
  

Record of JWST Operations Pipeline builds

Table 1 provides a historical record of JWST operations builds, along with links to the build release notes and tagged software versions. The "CRDS Context" column indicates the fixed context used by default by each pipeline version. Note that many intermediate development tags of the JWST Science Calibration Pipeline (indicated by minor version releases of the jwst package) are never installed in STScI DMS operations, but can be installed by end users. For full information on all jwst releases, see the github software version table.

Table 1. Release notes and associated versions for JWST Operations Pipeline releases

What's new in the latest build?

The latest released JWST Calibration Pipeline is build 12.3. Some highlights are provided here about major relevant changes; please refer to the build 12.3 release notes for additional details.

Please also refer to the calibration notes broken down by instrument mode in the JWST calibration status articles, and the known issues with JWST data articles for instrument-specific information.

Major pipeline updates in build 12.3

• Support for three new observing modes:
  • NIRCam Dispersed Hartmann Sensor (DHS) (short wavelength grism time series),
  • NIRISS SOSS multistripe (brighter targets via sequential subarray readouts), and
  • MIRI wide field slitless spectroscopy.
• NIRISS SOSS spectral extraction runtime is decreased by a factor of 30 or more (depending on the number of integrations).
• Automatic 1/f correction (clean_flicker_noise step) is now applied for NIRISS Imaging and WFSS, along with a new correction for SOSS time series.  The corresponding rms noise in SOSS light curves has improved by a factor of 5–20 (depending on source magnitude).
• Implemented an optional correction (adaptive_trace_model step) for resampling noise in MIRI MRS and NIRSpec IFU data cubes. See Resampling Artifacts for further information.
• Implemented an optional spectral contamination correction (wfss_contam step) for NIRCam, NIRISS, and MIRI wide field slitless spectroscopy.  This correction is currently off by default but may be enabled in a future build.
• Implemented optional correction for NIRSpec thermal picture frame artifacts (picture_frame step).
• Improved the robustness of the MIRI MRS residual fringe correction.
• Deprecated the MIRI firstframe step and updated the rscd step to reject more groups at the start of integrations, if doing so does not result in a null slope estimate. This helps mitigate the impact of systematic reset effects at the start of each ramp; see MIRI Known Issues for further information.
• Migrated to a new package (scikit-image) for characterizing large cosmic ray snowball and shower artifacts.
• Updated major jwst version number to 2.0.0 due to multiple major changes to pipeline architecture, dependencies, and default behavior for uninitialized variables. See detailed Release Notes for information on potentially breaking changes for advanced users.

Major reference file updates in build 12.3

Build 12.3 is tied to the CRDS reference file context 1535. A full list of CRDS context updates can be found at https://jwst-crds.stsci.edu/display_all_contexts/. Significant reference file deliveries included in this context include:

• Updated to the NIRISS SOSS (jwst_1490.pmap), NIRISS WFSS (jwst_1498.pmap), and NIRCam WFSS and TS grism (jwst_1469.pmap, jwst_1480.pmap) spectral trace models.
• Updated the NIRISS photometric calibration for all observing modes (jwst_1467.pmap, jwst_1476.pmap, and jwst_1483.pmap). These new files are incompatible with prior pipeline versions.
• Updated the NIRSpec IFU distortion solution, pixel area, and photometric calibration (jwst_1496.pmap and jwst_1534.pmap). This major update refines the spatial scale and spectral tilt of the IFU model, correcting up to 0.05" relative offsets seen between IFU slices and removing up to 0.15 pixel quadrupolar patterns in the wavelength solutions. Point source fluxes will remain relatively unchanged, but the surface brightnesses of extended sources are expected to change slightly and decrease by approximately 3%.
• Updated NIRCam imaging aperture corrections (jwst_1491.pmap).
• Enabled single-group ramp fitting by default for multiple observing modes.
• Updates darks and bad pixel reference files for multiple observing modes.

Coming soon

The next JWST pipeline build is build 13.0 (release candidate expected Summer 2026).  The following list indicates some of the areas in which users can expect to see changes and updates in the coming months.

Pipeline development

Ongoing JWST Science Calibration Pipeline development work in build 13.0 includes:

• Improved treatment of persistence flagging
• Improvements to WFSS background subtraction

Reference files

Major reference file updates currently planned for build 13.0 include:

• Further updates to the NIRSpec IFU distortion solution.

Reference files

In the early phases of the JWST mission, reference file contexts updated frequently and data within MAST processed with a given build could thus have used different reference files.

As of build 11.1 (December 2024), JWST now uses a fixed CRDS reference file context for each pipeline build (see the CRDS overview and CRDS Migration to Quarterly Calibration Updates).

Ephemeris information

Note that ephemeris information (the 3-dimentional position and velocity as a function of time) for JWST can evolve between the initial processing of a dataset available through MAST and subsequent reprocessing of that data. The Flight Dynamics Facility (FDF) group at Goddard evaluates the ephemeris for JWST's orbit and releases a weekly update that includes the actual ephemeris up to a specific date, and a predicted ephemeris that is used for planning and executing upcoming observations. Both are stored in a database within minutes of the files being delivered by FDF, and the database is accessed by level 1 data processing in the operations pipeline. Subsequent weekly deliveries by FDF will update the predicted ephemeris database values.

To populate the ephemeris headers in the JWST data products, the JWST Data Management System (DMS) uses the definitive ephemeris values, or if they are not yet available, they use the predicted ephemeris values. Most data are initially processed with the predicted ephemeris values, while later reprocessing will use the definitive values. The header keyword EPH_TYPE lists if Definitive or Predicted was used. The ephemeris files (both definitive and predicted) are also ingested into MAST. The ephemeris is used for aberration correction in the WCS parameters in the science headers, so all science types are affected.

References

Bushouse, H., et al. 2023, Zenodo 
JWST Calibration Pipeline