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]

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 file can be processed or an ASN file listing multiple inputs can be used, in which case the processing steps will be applied to each input exposure, one at a time. 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