# Reference Files¶

The persistence step uses TRAPDENSITY, PERSAT, and TRAPPARS reference files.

## TRAPDENSITY Reference File¶

REFTYPE

TRAPDENSITY

Data model

TrapDensityModel

The TRAPDENSITY reference file contains a pixel-by-pixel map of the trap density.

### Reference Selection Keywords for TRAPDENSITY¶

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

Instrument

Keywords

FGS

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRCam

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRISS

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 TRAPDENSITY¶

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

Keyword

Data Model Name

DETECTOR

model.meta.instrument.detector

### Reference File Format¶

TRAPDENSITY reference files are FITS format, with 2 IMAGE extensions and 1 BINTABLE extension. The FITS primary HDU does not contain a data array. The format and content of the file is as follows:

EXTNAME

XTENSION

NAXIS

Dimensions

Data type

SCI

IMAGE

2

ncols x nrows

float

DQ

IMAGE

2

ncols x nrows

int

DQ_DEF

BINTABLE

2

TFIELDS = 4

N/A

The DQ_DEF extension contains the bit assignments used in the DQ array. It contains the following 4 columns:

TTYPE

TFORM

Description

BIT

integer

The bit number, starting at zero

VALUE

integer

The equivalent base-10 value of BIT

NAME

string

The mnemonic name of the data quality condition

DESCRIPTION

string

A description of the data quality condition

NOTE: For more information on standard bit definitions see: Data Quality Flags.

## PERSAT Reference File¶

REFTYPE

PERSAT

Data model

PersistenceSatModel

The PERSAT reference file contains a pixel-by-pixel map of the persistence saturation (full well) threshold.

### Reference Selection Keywords for PERSAT¶

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

Instrument

Keywords

FGS

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRCam

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRISS

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 PERSAT¶

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

Keyword

Data Model Name

DETECTOR

model.meta.instrument.detector

### Reference File Format¶

PERSAT reference files are FITS format, with 2 IMAGE extensions and 1 BINTABLE extension. The FITS primary HDU does not contain a data array. The format and content of the file is as follows:

EXTNAME

XTENSION

NAXIS

Dimensions

Data type

SCI

IMAGE

2

ncols x nrows

float

DQ

IMAGE

2

ncols x nrows

int

DQ_DEF

BINTABLE

2

TFIELDS = 4

N/A

The DQ_DEF extension contains the bit assignments used in the DQ array. It contains the following 4 columns:

TTYPE

TFORM

Description

BIT

integer

The bit number, starting at zero

VALUE

integer

The equivalent base-10 value of BIT

NAME

string

The mnemonic name of the data quality condition

DESCRIPTION

string

A description of the data quality condition

NOTE: For more information on standard bit definitions see: Data Quality Flags.

## TRAPPARS Reference File¶

REFTYPE

TRAPPARS

Data model

TrapParsModel

The TRAPPARS reference file contains default parameter values used in the persistence correction.

### Reference Selection Keywords for TRAPPARS¶

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

Instrument

Keywords

FGS

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRCam

INSTRUME, DETECTOR, DATE-OBS, TIME-OBS

NIRISS

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 TRAPPARS¶

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

Keyword

Data Model Name

DETECTOR

model.meta.instrument.detector

### Reference File Format¶

TRAPPARS reference files are FITS format, with 1 BINTABLE extension. The FITS primary HDU does not contain a data array. The format and content of the file is as follows:

EXTNAME

XTENSION

Dimensions

TRAPPARS

BINTABLE

TFIELDS = 4

The format and contents of the table extension is as follows:

Column name

Data type

Description

capture0

float

Coefficient of exponential capture term

capture1

float

Minus the reciprocal of capture e-folding time

capture2

float

The “instantaneous” capture coefficient

decay_param

float

Minus the reciprocal of decay e-folding time

At the present time, there are no persistence reference files for MIRI and NIRSpec. CRDS will return “N/A” for the names of the reference files if the persistence step is run on MIRI or NIRSpec data, in which case the input will be returned unchanged, except that the primary header keyword S_PERSIS will will have been set to ‘SKIPPED’.