Reference Files

The rscd correction step uses an RSCD reference file.

RSCD Reference File

REFTYPE:

RSCD

Data model:

RSCDModel

The RSCD reference file contains the number of groups to flag as ‘DO_NOT_USE’ based on readout mode and subarray size.

Reference Selection Keywords for RSCD

CRDS selects appropriate RSCD references based on the following keywords. RSCD is not applicable for instruments not in the table. All keywords used for file selection are required.

Instrument	Keywords
MIRI	INSTRUME, 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 RSCD

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

Keyword	Data Model Name
DETECTOR	model.meta.instrument.detector

Reference File Format

RSCD reference files are in FITS format. The number of groups to set to ‘DO_NOT_USE’ is contained in the first BINTABLE extension. The FITS primary HDU does not contain a data array. The BINTABLE extension uses the identifier EXTNAME = “RSCD_GROUP_SKIP” and the characteristics of the table columns are as follows:

Column name	Data type	Notes
subarray	char*13	FULL or subarray name
readpatt	char*8	SLOWR1, FASTR1, SLOW, or FAST
group_skip1	int	number of initial groups in integration 1 to flag
group_skip	int	number of initial groups in integration 2 and higher to flag

The entries subarray and readpatt are used as selection criteria, matching the exposure properties of the data. The column group_skip1 is the number of initial groups in Integration 1 to flag as ‘DO_NOT_USE’. The column group_skip is the number of initial groups to flag in each subsequent integration (integration 2 and higher). These groups are excluded to mitigate the non-linear effects of Reset Switch Charge Decay (RSCD).