Recent Developments

Major events or important changes in the JWST mission are posted in dated sections of this article. 

Please note the following:

  • For a list of new JDox articles and updates to existing articles, please go to JWST JDox Latest Updates

  • JDox has been updated for on-orbit performance. As Cycle 1 continues, ongoing calibration activities will continue to improve calibrations, which may result in further updates.

  • At the bottom of each article is a table that has information on when a page was published and when notable updates have been made. Get in the habit of checking those dates to know when updates have been made!

On this page

March 15, 2023 update

Patch for JWST Operational Pipeline Build 9.1

Lists of all relevant changes to the operational pipeline that was released with build 9.1 and patch build 9.1.1, on February 28, 2023, and patch 9.1.2 on March 15, 2023, are available at JWST Operational Pipeline Build 9.1 Release Notes.

Build 9.1 and patch 9.1.1

  • Updated the ramp_fitting and some other downstream steps to assign "NaN" to pixels for which a count rate cannot be computed, instead of zero.
  • Fixed the handling of NIRSpec "leakcal" exposures, including updates to the way they are associated with both target and background exposures in association files, and the way they are subtracted during calwebb_spec2 pipeline processing.
  • Fixed issues with the computation of the output WCS grid for resampled NIRSpec MOS and fixed slit data.
  • Fixed bugs in the application of flux calibration to NIRSpec IFU extended source data and the construction of NIRSpec IFU cubes.
  • Updated the NIRISS SOSS "Algorithme de Traitement des Orders ContAminée" (ATOCA) algorithms used for creating 1-D extracted spectra.
  • Adjusted the level1b FITS keyword values in science data products for TARG_RA and TARG_DEC to account for proper motion of the target.

Patch 9.1.2

  • The opencv-python package was added to the pipeline requirements to support the new snowball and shower correction in the jump step, which is now turned on by default.
  • Fixed an issue causing linked background exposures to not always get associated with their corresponding science exposures.

March 8, 2023 update

JWST Operational Pipeline Build 9.1

A list of all relevant changes to the operational pipeline that was released with build 9.1 and patch build 9.1.1, on February 28, 2023, is available at JWST Operational Pipeline Build 9.1 Release Notes.


  • Updated the ramp_fitting and some other downstream steps to assign "NaN" to pixels for which a count rate cannot be computed, instead of zero.
  • Fixed the handling of NIRSpec "leakcal" exposures, including updates to the way they are associated with both target and background exposures in association files, and the way they are subtracted during calwebb_spec2 pipeline processing.
  • Fixed issues with the computation of the output WCS grid for resampled NIRSpec MOS and fixed slit data.
  • Fixed bugs in the application of flux calibration to NIRSpec IFU extended source data and the construction of NIRSpec IFU cubes.
  • Updated the NIRISS SOSS "Algorithme de Traitement des Orders ContAminée" (ATOCA) algorithms used for creating 1-D extracted spectra.

December 14, 2022 update

APT Version 2022.7.2 Release

STScI released a new version of APT v2022.7.2 today. Cycle 2 GO/AR proposals must be submitted using APT v2022.7.2. This version includes a patch to create new Cycle 2 proposals from existing proposals, for example declined Cycle 1 General Observer and Director's Discretionary Time proposals. See the Release Notes and Previous APT Releases for more information.

News from December 6, 2022 and earlier

December 6, 2022 update

Delivery and freeze of materials and software supporting the Cycle 2 Call for Proposals

As stated below, the JWST Call for Proposals for Cycle 2 was released on November 15, 2022. As of today, December 6, 2022, all software and documentation in support of the call is available to proposers and will be frozen for the duration of the open call period, which closes at 8 p.m. US Eastern Standard Time on January 27, 2023. The extra time to update the JDox documentation—from November 15, 2022 to today—was granted to STScI in order to provide the most up-to-date information possible in support of Cycle 2 proposing.  

This documentation delivery and freeze includes the ETC, APT, the ancillary planning tools (visibility tools, JIST, backgrounds tool, etc.), and JDox itself.  As for JDox, all articles have been checked and updated when necessary to include the latest information available to date from in-orbit operations of the observatory and instrumentation. Articles intentionally not updated have been flagged with appropriate banners stating it.

Notable updates made prior to the documentation freeze are listed at the JWST JDox Latest Updates page. In addition, each article has a date stamp at the bottom of the page indicating when significant updates were made to it. 

If any changes or updates are deemed necessary by STScI during the freeze period, they will be communicated appropriately to the community at large.  

As always, you are encouraged to direct any questions to the JWST Help Desk. Good luck on your Cycle 2 proposals!

November 15, 2022 update

JWST Cycle 2 Call for Proposals

We are pleased to announce that the JWST Cycle 2 Call for Proposals for General Observer (GO) time has been released, with up to 5,000 hours available in this cycle. 

Proposals are due by 8 p.m. US Eastern Standard Time on January 27, 2023. The Cycle 2 Telescope Allocation Committee will meet in mid-April 2023, with selections announced in May 2023.

APT 2022.7.1, for use with Cycle 2 proposing, will be available to the public as of November 17, 2022.  The release date for Exposure Time Calculator for Cycle 2, ETC 2.0, has been set to December 6, 2022. Our documentation system will continue to be updated frequently over the next several weeks, but will be frozen on December 6, 2022, for the remainder of the Cycle 2 open proposal period. You can always check the JDox Latest Updates page to see what has been changed recently.

For more details, please consult the full suite of articles that make up the JWST Call for Proposals for Cycle 2. Questions may be submitted to the JWST Help Desk.

Micrometeoroid avoidance zone

NASA has announced the establishment of a "zone of avoidance" to help protect the observatory from damage due to micrometeoroids. This zone overlaps a portion of the normal field of regard, thus reducing viewing opportunities for many targets. The intention is to strongly limit the number of observations that need to be scheduled when the observatory is pointing in the avoidance zone. A new JDox article, JWST Micrometeoroid Avoidance Zone, provides more insight into this avoidance region. The Astronomer's Proposal Tool for Cycle 2 proposing (APT 2022.7.1, release date ) includes new features to help users understand their proposed observations in this context and help minimize observations in this region. More information on the APT implementation is available in the article APT Micrometeoroid Avoidance.

November 10, 2022 update

MIRI medium resolution spectrometer (MRS) science operations resumed on November 2, 2022 

Operations with this mode were paused on August 24, 2022 due to excess frictional torque in the grating wheel used for this mode. After careful analysis, a new operational strategy is in place to allow resumed use of this mode. STScI will be in contact with individual affected investigators regarding the re-scheduling of pending MIRI MRS observations.

JWST PUB CRDS server to be decommissioned

As of November 10, 2022, all observers should be using the standard CRDS OPS server ( for obtaining the best JWST calibration reference files. The alternate PUB server ( that was available prior to that date will be decommissioned soon. For more information, please see the JWST Observer announcement or refer to the JDox article on JWST Data Calibration Reference Files.

September 26, 2022 update

NIRSpec news

  • The NIRSpec instrument model was updated in APT 2022.5.3 and released in mid-September 2022. The instrument model includes the detailed conversion of pixel positions to the sky based on updated astrometric solutions for the instrument. Any observations that use the NIRSpec MSA for target acquisition or for multi-object spectroscopy will be impacted by this update. (Affected users have been contacted directly.)  
  • A problem with NIRSpec nods was also corrected in the APT 2022.5.3 release.
  • See the APT release notes for more information.

MIRI news

  • On August 24, 2022, the grating wheel on the MIRI MRS channel experienced excess friction, and NASA has decided to study this situation carefully prior to restarting use of this observing mode. MIRI’s other 3 observing modes—imaging, low-resolution spectroscopy, and coronagraphy—are operating normally and remain available for science observations. Stay tuned for updates when more details become available.
  • In the APT 2022.5.3 update described above, a fix was applied to the MIRI coronagraphic background "repeat" option that now uses a quadrant opposite to the initial background.

July 12, 2022 initial post-commissioning news

JWST science performance report at the end of commissioning

A report on the actual JWST science performance, as characterized through the 6-month commissioning activities, is now available.

The JWST commissioning team has prepared a detailed report describing JWST's science performance as characterized in commissioning.  The report provides an excellent summary of the observatory and science instrument performance as it is known at the end of commissioning. Several highlights of most interest to observers include:

  • Slewing and pointing performance is as good or better than pre-mission expectations and guide star acquisitions are working well. Guiding performance is also excellent, with the pointing stability of the line of sight under fine guidance control several times better than the requirement. See section 2.4 and all of section 3 of the report.

  • The science instruments are meeting or exceeding their requirements (see section 6 of the report). Overall throughput is generally higher than pre-mission expectations, with up to 30% increased sensitivity for some instrument modes and wavelengths. This has at least 2 ramifications of interest to the user community:

    • Until full sensitivity details are known from commissioning, which will enable proper updates to the Exposure Time Calculator (ETC) and JWST Interactive Sensitivity Tool (JIST), these tools will generally underpredict actual performance in most cases. Both tools will be updated prior to the Cycle 2 Call for Proposals.

    • At this time, the JWST Project is not recommending that observers update their programs or their APT files for this effect since the signal-to-noise ratio in observations will usually be higher than predicted. The only exception is for very bright targets that were predicted to saturate in the second group (and that could now, in principle, saturate within the first group). Any programs containing such targets should be carefully reconsidered prior to observation. For questions or concerns, please contact your program coordinator or the JWST Help Desk.

  • The JWST background levels are a combination of multiple components that vary with time, orientation, wavelength, and observatory conditions. It will take time to fully characterize these components and their variability, and to get the changes into the various planning tools. However, commissioning data are largely consistent with predictions; if anything, near-IR backgrounds may be somewhat lower than expected. See section 5 of the report for details.

Artifacts seen in JWST data

See also: Data Features and Artifacts

In-flight experience has identified a number of artifacts and features that may appear in data, depending on circumstances at the time a given data set was obtained. Some of these effects are seen in data from multiple instruments while others are specific to a given instrument. The Data Features and Artifacts article has pointers to currently available information.

The user community will certainly want to be on the lookout for any of these features in science data and identify them appropriately. If you see anomalies in your data, contact the JWST Help Desk, as ongoing operations can help STScI characterize and possibly mitigate these effects going forward.

Caveats and limitations of the science calibration pipeline

See also: Section 7 in Characterization of JWST Science Performance from Commissioning.

Oct. 4, 2022 update: Because of the dynamic nature of the science calibration pipeline and data processing subsystem, as well as frequent reference file updates early in the mission, early JWST publications should include the CAL_VER, SDP_VER, and CRDS_CTX entries from the relevant data headers so that future researchers can place these results in proper context. For example, an independent researcher may use a version of the data with a later calibration, which may affect a comparison to the earlier data presentation. Given that there are currently 2 servers available for retrieving calibration reference data (CRDS-PUB or CRDS-OPS) and these may provide different versions of the data, publications should also indicate which server was used. See the JWST Calibration Pipeline Caveats article for further details.

The JWST Science Calibration Pipeline software performs nominal processing of JWST data for the many different instruments and instrument modes, making science-ready data products available to users. However, early in the mission, the pipeline software as well as the available calibration reference files are expected to be dynamic, with the scheduling of new software builds as experts implement improvements to the current algorithms or address features and artifacts found during in-flight operations. However, even with these improvements, it is impossible to accommodate certain specialized data processing schemes within the context of a standard pipeline processing system. The bottom line for JWST users is that early data will likely need to be reprocessed as improved information becomes available.

Science data will be reprocessed periodically as new versions of the JWST Science Calibration Pipeline are released and/or as new reference files become available. Use the MAST Portal to subscribe to observations of interest; you will then receive notifications when recalibrated products appear in the Archive for that observation. See the "Program Subscriptions and Notificationschapter of the MAST Portal Users Guide for information on how to subscribe. 

If your data were reprocessed due to changes in the JWST Science Calibration Pipeline, please refer to this article, JWST Pipeline Build Information, for release notes about those software changes.

In this release of JDox (on July 12, 2022), STScI is publishing a suite of articles outlining the currently known caveats and limitations of the pipeline products for many of the instrument modes. New articles will be added and the existing articles will be updated as more information becomes available, so check back frequently. 

An important point, mentioned above, that bears repeating: due to the dynamic nature of the science calibration pipeline, as well as frequent reference file updates early in the mission, early JWST publications should include the following information:

  • The CAL_VER and CRDS_CTX entries from the relevant data headers
  • The server used to retrieve reference files (CRDS-PUB or CRDS-OPS)

This is needed so that future researchers can reproduce results and retrospectively assess calibration issues or the need to recalibrate the data. Please see the JWST Calibration Pipeline Caveats article for more details.

A heads-up to NIRSpec MOS/MSATA users

See also: NIRSpec MPT - Catalogs and NIRSpec MSA Target Acquisition

Initial experience with the NIRSpec MOS observing highlights the need for careful vetting of the astrometry derived from pre-imaging against source positions in the Gaia catalog. In particular, the MSA target acquisition procedure has a very limited ability to correct for errors in the initial roll, and so it is essential that the rotation of the reference stars on the sky be aligned with that of the Gaia frame to better than 30” in rotation. Care should be taken to consider any proper motion of the Gaia stars and reference stars to avoid introducing a spurious roll offset larger than this. Early NIRCam pre-imaging observations are included in this requirement until camera distortions are better characterized and included in the NIRCam data processing pipeline. Since this is a dynamic area with ongoing development, it is best to contact your program coordinator and NIRSpec instrument scientist or the JWST Help Desk for more details.

JWST data analysis tool (JDAT) video tutorials now available

All early release observations (ERO) and commissioning data became public during the ERO release on July 12, 2022. Also, as Director's Discretionary Early Release Science program data are obtained (primarily over the first 5 months of science operations), those data will immediately be publicly available. You are encouraged to grab some public data and investigate it!

A number of new videos on the JWST data analysis tools suite (JDAT; Imviz, Specviz, and Cubeviz) are posted at the JWST Observer YouTube channel. A convenient tabular listing with summary descriptions and direct links to each video is now available at JWST Data Analysis Tool Video Tutorials.

Users may also refer to the videos and support materials from the previous JWebbinar series (open the "Materials and Videos" tab) to get started on working with JWST data.

Looking for JWST data?

Everything you need to get started is available from the Accessing JWST Data article. Don't forget to check the pedigree of existing data in MAST by checking the CRDB context of the calibration files applied to the data set of interest. See the JWST Calibration Pipeline Caveats article (and in particular, the section on CRDS reference file status) for details. Good luck!

Publishing JWST data

As a reminder, please refer to the red box above dated Oct. 4, 2022, for information regarding referencing of the heritage of your data and data processing. When publishing JWST data, please remember to add the appropriate standard acknowledgements, examples of which are shown in MAST. Also, paper authors are obliged to include a digital object identifier (DOI) that points to the data they analyzed. Instructions for doing that can be found in the Special Searches article that is part of the MAST Portal Guide.

The JWST Director's Discretionary Time program

Coinciding with the July 12, 2022 release of Early Release Observations, the opportunity to propose for JWST Director’s Discretionary Time (DDT) has been opened to the astronomy community! Consistent with the policies for DDT proposals, they should be proposed for time-critical observations that are unable to wait to go through the regular TAC process.

Cycle 2 Guaranteed Time Observer call for proposals

JWST Guaranteed Time Observers (GTOs) are invited to submit Cycle 2 GTO science proposals. The details for submitting proposals can be found in the JWST Cycle 2 GTO Call for Proposals, which has just been released. 

Latest updates
    Information about JWST Operational Pipeline Build 9.1

    Announcement about release of APT v2022.7.2 

    Announcement of Cycle 2 software and documentation freeze.

    Announcement about Cycle 2 Call for Proposals and the micrometeoroid avoidance zone (MAZ)

    MIRI MRS resumed operations, JWST PUB CRDS server to be decommissioned

    Update on how to express the heritage of data products in publications

    Updated information on MIRI MRS and NIRSpec performance 

    Added pointer to DOI information in the Publication section
Originally published