Reference Files

The residual_fringe step uses the FRINGEFREQ reference file.

FRINGEFREQ reference file

REFTYPE:

FRINGEFREQ

Data models:

FringeFreqModel

The FRINGEFREQ reference files contain parameter values used to correct MIRI MRS images for residual fringes that remain after applying the fringe flat.

Reference Selection Keywords for FRINGEFREQ

CRDS selects appropriate FRINGEFREQ reference file based on the following keywords. FRINGEFREQ is not applicable for instruments not in the table.

Instrument	Keywords
MIRI	INSTRUME, EXP_TYPE, DETECTOR, 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 FRINGEFREQ

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

Keyword	Data Model Name
DETECTOR	model.meta.instrument.detector
EXP_TYPE	model.meta.exposure.type

Reference File Format

The FRINGEFREQ reference files are FITS format, with 4 BINTABLE extensions. The FITS primary data array is assumed to be empty. The format and content of the FRINGEFREQ reference file is

EXTNAME	XTENSION	Dimensions
RFC_FREQ_SHORT	BINTABLE	TFIELDS = 7
RFC_FREQ_MEDIUM	BINTABLE	TFIELDS = 7
RFC_FREQ_LONG	BINTABLE	TFIELDS = 7
MAX_AMP	BINTABLE	TFIELDS = 2

The formats of the individual table extensions are listed below.

Table	Column	Data type	Units
RFC_FREQ_SHORT	SLICE	double	N/A
	FFREQ	double	cm-1
	DFFREQ	double	cm-1
	MIN_NFRIGES	int	N/A
	MAX_NFRINGES	int	N/A
	MIN_SNR	double	cm-1
	PGRAM_RES	double	cm-1
FRC_FREQ_MEDIUM	SLICE	double	N/A
	FFREQ	double	cm-1
	DFFREQ	double	cm-1
	MIN_NFRIGES	int	N/A
	MAX_NFRINGES	int	N/A
	MIN_SNR	double	cm-1
	PGRAM_RES	double	cm-1
RFC_FREQ_LONG	SLICE	double	N/A
	FFREQ	double	cm-1
	DFFREQ	double	cm-1
	MIN_NFRIGES	int	N/A
	MAX_NFRINGES	int	N/A
	MIN_SNR	double	cm-1
	PGRAM_RES	double	cm-1
MAX_AMP	WAVELENGTH	double	micron
	AMPLITUDE	double	N/A

These reference files contain tables for each MIRI band giving the fringe frequencies and other parameters for each band to fit and remove residual fringes.

The reference table descriptions:

• RFC_FREQ_SHORT table contains the fringe frequencies and parameters for the SHORT band.

• RFC_FREQ_MEDIUM table contains the fringe frequencies and parameters for the MEDIUM band.

• RFC_FREQ_LONG table contains the fringe frequencies and parameters for the LONG band.

• MAX_AMP table contains a wavelength dependent maximum amplitude which is use for feature identification and fit rejection.