calwebb_image2: Stage 2 Imaging Processing

Class:

jwst.pipeline.Image2Pipeline

Alias:

calwebb_image2

Stage 2 imaging processing applies additional instrumental corrections and calibrations that result in a fully calibrated individual exposure. There are two parameter references used to control this pipeline, depending on whether the data are to be treated as Time Series Observation (TSO). The parameter reference is provided by CRDS and the reftype pars-image2pipeline. In general, for non-TSO exposures, all applicable steps are applied to the data. For TSO exposures, some steps are set to be skipped by default (see the list of steps in the table below).

The list of steps applied by the Image2Pipeline pipeline is shown in the table below.

Step	Non-TSO	TSO
background	✓
assign_wcs	✓	✓
flat_field	✓	✓
photom	✓	✓
resample [1]	✓

[1]

Resampling is only performed for exposure types “MIR_IMAGE”, “NRC_IMAGE”, and “NIS_IMAGE”.

Arguments

The calwebb_image2 pipeline has one optional argument:

--save_bsub  boolean  default=False

If set to True, the results of the background subtraction step will be saved to an intermediate file, using a product type of “_bsub” or “_bsubints”, depending on whether the data are 2D (averaged over integrations) or 3D (per-integration results).

Inputs

2D or 3D countrate data

Data model:

ImageModel or CubeModel

File suffix:

_rate or _rateints

The input to Image2Pipeline is a countrate exposure, in the form of either “_rate” or “_rateints” data. A single input FITS file can be processed or an ASN file can be used, as long as there is only one output product specified in the association. If “_rateints” products are used as input, each step applies its algorithm to each integration in the exposure, where appropriate.

TSO and coronagraphic exposures are expected to use 3D data as input, to be processed on a per-integration basis.

Outputs

2D or 3D background-subtracted data

Data model:

ImageModel or CubeModel

File suffix:

_bsub or _bsubints

This is an intermediate product that is only created if “–save_bsub” is set to True and will contain the data as output from the background step. If the input is a “_rate” product, this will be a “_bsub” product, while “_rateints” inputs will be saved as “_bsubints.”

2D or 3D calibrated data

Data model:

ImageModel or CubeModel

File suffix:

_cal or _calints

The output is a fully calibrated, but unrectified, exposure, using the product type suffix “_cal” or “_calints”, depending on the type of input, e.g. “jw80600012001_02101_00003_mirimage_cal.fits”.

2D resampled image

Data model:

ImageModel

File suffix:

_i2d

This is the output of the resample step and is only created for regular direct imaging observations (not for TSO or coronagraphy 3D data sets). The output file will use the “_i2d” product type suffix, e.g. “jw80600012001_02101_00003_mirimage_i2d.fits”. Note that this product is intended for quick-look use only and is not passed along as input to Stage 3 processing. Calibrated, but unrectified (_cal) products are used as input to Stage 3.

PARS-IMAGE2PIPELINE Parameter Reference File

REFTYPE:

PARS-IMAGE2PIPELINE

Data model:

N/A

Reference Selection Keywords

CRDS selects appropriate pars-image2pipeline references based on the following keywords.

Instrument	Keywords
FGS	EXP_TYPE, TSOVISIT, VISITYPE
MIRI	EXP_TYPE, TSOVISIT, VISITYPE
NIRCAM	EXP_TYPE, TSOVISIT, VISITYPE
NIRISS	EXP_TYPE, TSOVISIT, VISITYPE
NIRSPEC	EXP_TYPE, TSOVISIT, VISITYPE

Standard Keywords

The following table lists the keywords that are required to be present in all reference files. The first column gives the FITS keyword names. The second column gives the jwst data model name for each keyword, which is useful when using data models in creating and populating a new reference file. The third column gives the equivalent meta tag in ASDF reference file headers, which is the same as the name within the data model meta tree (second column).

FITS Keyword	Data Model Name	ASDF meta tag
AUTHOR	model.meta.author	author
DATAMODL	model.meta.model_type	model_type
DATE	model.meta.date	date
DESCRIP	model.meta.description	description
FILENAME	model.meta.filename	N/A
INSTRUME	model.meta.instrument.name	instrument: {name}
PEDIGREE	model.meta.pedigree	pedigree
REFTYPE	model.meta.reftype	reftype
TELESCOP	model.meta.telescope	telescope
USEAFTER	model.meta.useafter	useafter

NOTE: More information on standard required keywords can be found here: Standard Required Keywords