Reference Files

The straylight step uses the MRSXARTCORR reference file, which stores vectors describing the appropriate cross-artifact convolution kernel for each MRS band. In Channel 1 these vectors include power in a broad Lorentzian core plus a pair of double-Gaussian profiles. In Channels 2 and 3 these vectors include only power in the broad Lorentzian, while in Channel 4 there is no correction.

Optionally, the straylight step can also use the REGIONS reference files during correction of residual cosmic ray showers. These reference files describe the footprint of the dispersed IFU traces on the detector and are used to identify inter-slice pixels that do not see direct light from the sky.

MRSXARTCORR reference file

REFTYPE:

MRSXARTCORR

Data models:

MirMrsXArtCorrModel

The MRSXARTCORR reference file contains parameter values used to model and subtract the cross-artifact in the straylight step.

Reference Selection Keywords for MRSXARTCORR

CRDS selects appropriate MRSXARTCORR references based on the following keywords. MRSXARTCORR is not applicable for instruments not in the table.

Instrument	Keywords
MIRI	INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

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

Type Specific Keywords for MRSXARTCORR

In addition to the standard reference file keywords listed above, the following keywords are required in MRSXARTCORR reference files, because they are used as CRDS selectors (see Reference Selection Keywords for MRSXARTCORR):

Keyword	Data Model Name
EXP_TYPE	model.meta.exposure.type

MIRI Reference File Format

The MIRI MRSXARTCORR reference files are FITS format, with 12 BINTABLE extensions. The FITS primary data array is assumed to be empty. The format and content of the MIRI MRSXARTCORR reference file

EXTNAME	XTENSION	Dimensions
1A	BINTABLE	TFIELDS = 7
1B	BINTABLE	TFIELDS = 7
1C	BINTABLE	TFIELDS = 7
2A	BINTABLE	TFIELDS = 7
2B	BINTABLE	TFIELDS = 7
2C	BINTABLE	TFIELDS = 7
3A	BINTABLE	TFIELDS = 7
3B	BINTABLE	TFIELDS = 7
3C	BINTABLE	TFIELDS = 7
4A	BINTABLE	TFIELDS = 7
4B	BINTABLE	TFIELDS = 7
4C	BINTABLE	TFIELDS = 7

The formats of the individual table extensions are listed below.

Table	Column	Data type	Units
CH1A	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH1B	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH1C	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH2A	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH2B	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH2C	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH3A	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH3B	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH3C	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH4A	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH4B	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A
CH4C	YROW	shortint	pixels
	LOR_FWHM	float	pixels
	LOR_SCALE	float	N/A
	GAU_FWHM	float	pixels
	GAU_XOFF	float	pixels
	GAU_SCALE1	float	N/A
	GAU_SCALE2	float	N/A

These reference files contain tables for each wavelength band giving the appropriate kernel properties to use to model the cross-artifact for each band. These include Lorentzian plus Gaussian models.

The MIRI reference table contains parameters for each band in the corresponding EXTNAME extension.