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This page provides information on the reference files used by the JWST pipeline to process NIRISS data. The information is sorted by pipeline stages. Detailed information on the pipeline steps and files format is provided in the specified links.


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Introduction

The JWST NIRISS instrument offers 4 science observing modes that are automatically processed by the JWST pipeline: wide field slitless spectroscopy, single object slitless spectroscopy, aperture masking interferometry, and imaging.  The following sections provide information on the NIRISS-specific reference files used by the pipeline, organised according to the different pipeline stages. 

 


CALWEBB_DETECTOR1

This pipeline stage process the LVL1 up-the-ramp raw files and returns the level 2a files in units of (counts/sec). All NIRISS data goes though the entire set of pipeline steps applied in CALDETECTOR1. To achieve that several the diverse steps in the correspondent NIR pipeline flow use the following reference files:  

Table 1. NIRISS reference files used by the JWST pipeline module calwebb_detector1.

Pipeline step

Reference files used

Usability notes

Data Quality Initialisation

jwst_niriss_mask_xxxx.fits

 

Saturation check

jwst_niriss_saturations_xxxx.fits

 

Interpixel Capacitance Correction

jwst_niriss_ipc_xxxx.fits

Step included in the pipeline, but disabled by default.

Superbias Subtraction

jwst_niriss_superbias_xxxx.fits

One reference file per readout mode/subarray.

 

Reference Pixels Correction

N/A. The correction uses reference pixels information stored in each exposure

 

Linearity Correction

jwst_niriss_linearity_xxxx.fits

 

Persistence Correction

Persat: jwst_niriss_persat_xxxx.fits

Trap density: jwst_niriss_trapdensity_xxxx.fits

Trap pars: jwst_niriss_trappars_xxxx.fits

 

Dark Subtraction

jwst_niriss_dark_xxxx.fits

One reference file per readout mode/subarray.

 

Jump Detection

Gain: jwst_niriss_gain_xxxx.fits

Read noise: jwst_niriss_readnoise_xxxx.fits

 

Ramp fit

Gain: jwst_niriss_gain_xxxx.fits

Read noise: jwst_niriss_readnoise_xxxx.fits

 

 


CALWEBB_Dark

This pipeline branch is intended for use with dark exposures. It applies all of the same detector-level correction steps as CALWEBB_Slopes and uses the same reference files, but stops just before the application of the dark subtraction step.

 


CALWEBB_IMAGE2 reference files

In this pipeline stage individual exposures from the imaging modes are processed from counts/sec to absolute flux units.  Details on the pipeline steps flow are given here.

Table 2. NIRISS reference files used by the JWST pipeline module calwebb_image2.

 

 

Pipeline step

 

 

Reference files used

 

 

Usability notes

 

Assign WCS Information

Distortion file: jwst_niriss_distortion_xxxx.asdf

 

Background Subtraction

Step does not use any reference file.

Step applies to science data if the user requests a dedicated background image. 

Not applied to Target Acquisition images. 

Flat Field Correction

Flat field: jwst_niriss_flat_xxxx.fits

 

Flux Calibration

Photom: jwst_niriss_photom_xxxx.fits

Area: jwst_niriss_area_xxxx.fits

Not applied to Target Acquisition images.

Rectify 2D image

Step does not use any reference file.

 

 


CALWEBB_SPEC2 reference files

This pipeline stage process Individual exposures from the spectroscopic modes from counts/sec to absolute flux and wavelength units.  Nominally, this stage works on individual exposures obtained for the NIRISS wide field slitless grism observations, but the steps are not yet implemented.

Table 3. NIRISS reference files used by the JWST pipeline module calwebb_spec2.

 

Pipeline step

 

 

Reference files used

 

 

Usability notes

 

Assign WCS Information

Distortion file: jwst_niriss_distortion_xxxx.asdf

 

Background Subtraction

WFSS uses a reference file (To be defined).

SOSS uses a reference file (master background).  

 

Subwindow extraction

Step does not use any reference file.

 
extract_2djwst_niriss_wavecorr_xxxx.asdfStep applied in NIRISS WFSS only

Flat Field

Flat file: jwst_niriss_flat_xxxx.fits

 

Point vs Extended Decision

Step does not require any reference file

 

Photometric Correction

Photom file: jwst_niriss_photom_xxxx.fits

Area: jwst_niriss_area_xxxx.fits

 

Rectified 2D 3D product

  

Spectral Extraction 1d

jwst_niriss_extract1d_xxxx.json

 

 


CALWEBB_IMAGE3 reference files

Multiple exposures from the direct imaging modes (e.g., dither pattern or mosaic) are combined into a single rectified (distortion corrected) image. Details on the pipeline steps flow are given in this page.

Table 4. NIRISS reference files used by the JWST pipeline module calwebb_image3.

Pipeline step

Reference files used

Usability notes

Tweakreg Catalog

Step does not use any reference file.

 

Tweakreg

Step does not use any reference file.

 

Skymatch

Step does not use any reference file.

 

Outlier_detection

Step does not use any reference file.

 

Resample

Step does not use any reference file.

 

Source_catalog

Step does not use any reference file.

 

 


CALWEBB_SPEC3

Multiple individual exposures for the spectroscopic modes (i.e. dither patters or mosaics) are combined into a single rectified cube and/or extracted spectrum.

Table 5. NIRISS reference files used by the JWST pipeline module calwebb_spec3.

 

Pipeline step

 

 

Reference files used

 

 

Usability notes

 

Outlier Detection

Step does not require any extra reference file.

 

Create Exp Level Products

  

Cube Creation

Step does not use any reference file. 

 

Spectral Extraction 1D

jwst_niriss_extract1d_xxxx.json

  

 


CALWEBB_AMI3

The Level-3 Aperture Mask Interferometry pipeline is intended to be applied to associations of individual calibrated NIRISS AMI exposures and is used to compute fringe parameters and correct science target fringe parameters using observations of reference targets. Details on the individual pipeline steps can be found here.

Table 6. NIRISS reference files used by the JWST pipeline module calwebb_ami3.

 

Pipeline step

Reference files used

Usability notes

Analize

jwst_niriss_throughput_xxxx.fits

 

Average

Step does not use any reference file.

 

Normalize

Step does not use any reference file.

 

 


 



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References

JWST technical documents

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Last updated

Updated July 15, 2017

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Published July 11, 2017


 

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