Stages of JWST Data Processing

The processing of JWST data goes through three stages. Stage 1 processes the raw data to produce count rate (slope) images. Stage 2 calibrates the slope images. Stage 3 carries out additional processing, including the ability to work with multiple exposures to create combined images and spectra..

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Science calibration pipeline stages

See also: JWST Data Calibration Considerations, Algorithm Documentation, Understanding JWST Data Files, JWST Science Calibration Pipeline Overview 

There are 3 main calibration pipeline stages required to completely process a set of exposures for a given observation:

  • Stage 1: Apply detector-level corrections to the raw data for individual exposures and produce count rate (slope) images from the "ramps" of non-destructive readouts
  • Stage 2: Apply physical corrections (e.g., slit loss) and calibrations (e.g., absolute fluxes and wavelengths) to individual exposures
  • Stage 3: Combine the fully calibrated data from multiple exposures
The JWST science calibration pipeline has three main stages that provide data to the archive (see Figure 1).  Each stage is composed of multiple steps (i.e., modules), which differ according to the type of observation. A summary of the input and output data for each stage are shown below, along with the type of observations that are run through the different modules.
Figure 1. JWST science calibration pipeline structure

The overall JWST science calibration pipeline structure and flow is shown. All the data start at the top and the processing becomes more specific to the particular type of observations as the data flow through the calibration pipeline. All modules in the calibration pipeline contribute processed data to the archive. Note that the "CALWEBB_" prefix has been omitted from the module names.

Stage 1

This stage applies detector-level corrections to raw non-destructively read "ramps" in order to produce count rate images per exposure, or per integration for some modes.

  • Input: raw ramps for all integrations
  • Output: uncalibrated slope images for all integrations and exposures
  • CALWEBB_DETECTOR1: applied for all data

Stage 2

See also: JWST Data Associations

This stage applies physical corrections and calibrations to individual exposures to produce fully calibrated (unrectified) exposures.

  • input: uncalibrated slope images for all integrations and exposures
  • output: calibrated slope images for all integrations and exposures
  • CALWEBB_IMAGE2: applied to all imaging data (including coronagraphy and AMI)
  • CALWEBB_SPEC2: applied to all spectroscopic data

Stage 3

See also: JWST Data Associations

This stage combines the fully calibrated data from multiple exposures.

  • input: calibrated slope images for all integrations and exposures
  • output: combined, rectified level-3 data
  • CALWEBB_IMAGE3: applied to direct imaging data
    • output: coadded image(s) (e.g., mosaic), catalog of sources, updated exposure level products
  • CALWEBB_CORON3: applied to coronagraphic data
    • output: coadded image(s), and updated exposure level products
  • CALWEBB_AMI3: applied to NIRISS Aperture Masking Interferometry data
  • CALWEBB_SPEC3: applied to spectroscopic data
    • output: coadded spectral cube, extracted 1D spectrum, and updated exposure level products
  • CALWEBB_TSO3: applied to all time series observations (photometry and spectroscopy)
    • output: photometry and 1D spectroscopy for each integration and exposure, and updated exposure level products



Stages of processing by observation type

See also: JWST Observing Template

The full list of exposure type versus calibration pipeline stage is shown in the science calibration pipeline software documentation. Table 1 below shows the calibration pipeline modules used to process the data from each JWST Observing Template.


Table 1. Science Calibration Pipeline Modules vs. Observing Template

Pipeline ModuleObserving Template
CALWEBB_DETECTOR1All
CALWEBB_IMAGE2

NIRCam Imaging

NIRCam Coronagraphic Imaging

NIRCam TSO Imaging

NIRISS AMI

NIRISS Imaging

MIRI Imaging

MIRI Coronagraphic Imaging

All Target Acquisition Imaging

FGS Science/Guide Imaging

CALWEBB_SPEC2

NIRCam WFSS

NIRCam TSO Grism

NIRSpec MOS

NIRSpec FS spectroscopy

NIRSpec IFU spectroscopy

NIRSpec BOTS / TSO spectroscopy

NIRISS SOSS

NIRISS WFSS

MIRI LRS

MIRI MRS

CALWEBB_IMAGE3

NIRCam Imaging

NIRISS Imaging

MIRI Imaging

CALWEBB_CORON3

NIRCam Coronagraphic Imaging

MIRI Coronagraphic Imaging

CALWEBB_AMI3

NIRISS AMI

CALWEBB_SPEC3

NIRCam WFSS

NIRSpec MOS

NIRSpec FS Spectroscopy

NIRSpec IFU Spectroscopy

NIRISS WFSS

MIRI LRS

MIRI MRS

CALWEBB_TSO3

NIRCam TSO Imaging

NIRCam TSO Grism

NIRSpec BOTS / TSO Spectroscopy

NIRISS SOSS

MIRI Imaging (TSO option)

MIRI LRS (TSO option)

MIRI MRS (TSO option)



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  • Addressed v1.1 comments.

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