JWST Data Calibration Considerations

The JWST calibration program is charged with obtaining the necessary reference files used by the JWST Science Calibration Pipeline to remove instrumental signatures and produce data products that are absolutely calibrated. 

Ongoing calibration 

Aspects of the Cycle 1 calibration plan will be executed throughout the coming months. Expect frequent updates to calibration reference files and reprocess your data when needed. 

Please refer to JWST Calibration Pipeline Caveats for more information.

On this page

See also: JWST Data Absolute Astrometric CalibrationJWST Data Absolute Flux CalibrationJWST Data Absolute Wavelength CalibrationJWST Data Calibration Reference Files

Absolute calibration

The requirements for the JWST absolute flux, wavelength, and position calibration are given in the tables below. At this point, we expect to meet all these requirements. The planned calibration programs are sufficient to meet or exceed these requirements. 

Flux

The requirements for absolute flux calibration vary by instrument and observation mode. They are listed in Table 1. For the details of targets, etc. see the JWST Data Absolute Flux Calibration article. Note that the needed flux prediction accuracy on the targets exceeds those listed in the table as there are other terms involved beyond the prediction accuracy (aperture correction accuracy, stability, etc.). 


Table 1. Absolute flux requirements

Instrument

Imaging

Coronagraphy

Spectroscopy

NIRCam

5%

5%

10%

NIRSpec

N/A

N/A

10%

NIRISS

5%

N/A

10% 

MIRI

5%

15%

15%


For sources observed through slits, the value is for well centered observations. 
 Not a formal requirement, by analogy with NIRSpec spectroscopy.

Wavelength

The requirements for absolute wavelength calibration vary by instrument. They are listed in Table 2. For the details of targets, etc., see the JWST Data Absolute Wavelength Calibration article. Note that the needed wavelength prediction accuracy on the targets exceeds those listed in the table as there are other terms involved beyond the prediction accuracy (aperture centering accuracy, stability, etc.). 


Table 2. Absolute wavelength requirements

Instrument

Accuracy
(resolution element)

NIRCam

10%*

NIRSpec

12.5%

NIRISS

10%

MIRI

10%

* Not a formal requirement, by analogy with NIRISS spectroscopy.

Position (astrometry)

The requirement for absolute position (astrometric) calibration is 5 mas. Specifically, the 5 mas refers to the uncertainty in the observatory field distortion correction within any instrument and the guider. For details see the article titled JWST Data Absolute Astrometric Calibration.



Cycle 1 calibration programs

The instrument Cycle 1 calibration programs will provide a set of deliverables needed to remove instrumental signatures and calibrate the JWST observations. The main deliverables from the calibration program are reference files for the science calibration pipeline. The Cycle 1 calibration program will be used in combination with any similar observations taken during the JWST commissioning to produce the highest quality reference files.

Example deliverables




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