Reference File Types

The source_catalog step uses APCORR, ABVEGAOFFSET, and PARS-SOURCECATALOGSTEP reference files.

APCORR Reference File

REFTYPE

APCORR

The APCORR reference file contains data necessary for correcting extracted imaging and spectroscopic photometry to the equivalent of an infinite aperture. It is used within the source_catalog step for imaging and within the extract_1d step for spectroscopic data.

Reference Selection Keywords for APCORR

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

Instrument

Keywords

FGS

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

MIRI

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRCam

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRISS

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRSpec

INSTRUME, EXP_TYPE, FILTER, GRATING, LAMP, OPMODE, 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 APCORR

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

Keyword

Data Model Name

Instruments

EXP_TYPE

model.meta.exposure.type

All

NON-IFU APCORR Reference File Format

APCORR reference files for non-IFU data are in FITS format. The FITS APCORR reference file contains tabular data in a BINTABLE extension with EXTNAME = ‘APCORR’. The FITS primary HDU does not contain a data array. The contents of the table extension varies for different instrument modes, as shown in the tables below.

Data model

FgsImgApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

FGS

Image

eefraction

float

scalar

unitless

radius

float

scalar

pixels

apcorr

float

scalar

unitless

skyin

float

scalar

pixels

skyout

float

scalar

pixels
Data model

MirImgApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

MIRI

Image

filter

string

12

N/A

subarray

string

15

N/A

eefraction

float

scalar

unitless

radius

float

scalar

pixels

apcorr

float

scalar

unitless

skyin

float

scalar

pixels

skyout

float

scalar

pixels
Data model

MirLrsApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

MIRI

LRS

subarray

string

15

N/A

wavelength

float

1D array

micron

nelem_wl

integer

scalar

N/A

size

integer

1D array

pixels

nelem_size

integer

scalar

N/A

apcorr

float

2D array

unitless

apcorr_err

float

2D array

unitless
Data model

NrcImgApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRCam

Image

filter

string

12

N/A

pupil

string

15

N/A

eefraction

float

scalar

unitless

radius

float

scalar

pixels

apcorr

float

scalar

unitless

skyin

float

scalar

pixels

skyout

float

scalar

pixels
Data model

NrcWfssApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRCam

WFSS

filter

string

12

N/A

pupil

string

15

N/A

wavelength

float

1D array

micron

nelem_wl

integer

scalar

N/A

size

integer

1D array

pixels

nelem_size

integer

scalar

N/A

apcorr

float

2D array

unitless

apcorr_err

float

2D array

unitless
Data model

NisImgApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRISS

Image

filter

string

12

N/A

pupil

string

15

N/A

eefraction

float

scalar

unitless

radius

float

scalar

pixels

apcorr

float

scalar

unitless

skyin

float

scalar

pixels

skyout

float

scalar

pixels
Data model

NisWfssApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRISS

WFSS

filter

string

12

N/A

pupil

string

15

N/A

wavelength

float

1D array

micron

nelem_wl

integer

scalar

N/A

size

integer

1D array

pixels

nelem_size

integer

scalar

N/A

apcorr

float

2D array

unitless

apcorr_err

float

2D array

unitless
Data model

NrsFsApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRSpec

FS

filter

string

12

N/A

grating

string

15

N/A

slit

string

15

N/A

wavelength

float

1D array

micron

nelem_wl

integer

scalar

N/A

size

integer

2D array

arcsec

nelem_size

integer

scalar

N/A

pixphase

float

1D array

N/A

apcorr

float

3D array

unitless

apcorr_err

float

3D array

unitless
Data model

NrsMosApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRSpec

MOS

filter

string

12

N/A

grating

string

15

N/A

wavelength

float

1D array

micron

nelem_wl

integer

scalar

N/A

size

integer

2D array

arcsec

nelem_size

integer

scalar

N/A

pixphase

float

1D array

N/A

apcorr

float

3D array

unitless

apcorr_err

float

3D array

unitless

Row Selection

A row of data within the reference table is selected by the pipeline step based on the optical elements in use for the exposure. The selection attributes are always contained in the first few columns of the table. The remaining columns contain the data needed for the aperture correction. The row selection criteria for each instrument+mode are:

  • FGS Image:

    • None (table contains a single row)

  • MIRI:

    • Image: Filter and Subarray

    • LRS: Subarray

  • NIRCam:

    • Image: Filter and Pupil

    • WFSS: Filter and Pupil

  • NIRISS:

    • Image: Filter and Pupil

    • WFSS: Filter and Pupil

  • NIRSpec:

    • MOS: Filter and Grating

    • Fixed Slits: Filter, Grating, and Slit name

Note: Spectroscopic mode reference files contain the “nelem_wl” and “nelem_size” entries, which indicate to the pipeline step how many valid elements are contained in the “wavelength” and “size” arrays, respectively. Only the first “nelem_wl” and “nelem_size” entries are read from each array.

IFU APCORR Reference File ASDF Format

For IFU data the APCORR reference files are in ASDF format. The aperture correction varies with wavelength and the contents of the files are shown below. The radius, aperture correction and error are all 2D arrays. Currently the 2nd dimension does not add information, but in the future it could be used to provide different aperture corrections for different radii.

Data model

MirMrsApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

MIRI

MRS

wavelength

float

1D array

micron

radius

float

2D array

arcsec

apcorr

float

2D array

unitless

apcorr_err

float

2D array

unitless
Data model

NRSIFUApcorrModel

Instrument

Mode

Column name

Data type

Dimensions

Units

NIRSpec

MOS

filter

string

12

N/A

grating

string

15

N/A

wavelength

float

1D array

micron

radius

float

2D array

arcsec

apcorr

float

2D array

unitless

apcorr_err

float

2D array

unitless

ABVEGAOFFSET Reference File

REFTYPE

ABVEGAOFFSET

Data model

ABVegaOffsetModel

The ABVEGAOFFSET reference file contains data necessary for converting from AB to Vega magnitudes.

Reference Selection Keywords for ABVEGAOFFSET

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

Instrument

Keywords

FGS

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

MIRI

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRCam

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRISS

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

ABVEGAOFFSET Reference File Format

ABVEGAOFFSET reference files are in ASDF format. The ABVEGAOFFSET reference file contains tabular data in a key called abvega_offset. The content of the table varies for different instrument modes, as shown in the tables below.

Instrument

Column name

Data type

Dimensions

Units

FGS

detector

string

7

N/A

abvega_offset

float

scalar

unitless

Instrument

Column name

Data type

Dimensions

Units

MIRI

filter

string

12

N/A

abvega_offset

float

scalar

unitless

Instrument

Column name

Data type

Dimensions

Units

NIRCam or NIRISS

filter

string

12

N/A

pupil

string

15

N/A

abvega_offset

float

scalar

unitless

Row Selection

A row of data within the reference table is selected by the pipeline step based on the optical elements in use for the exposure. The selection attributes are always contained in the first few columns of the table. The last column contains the data needed to convert from AB to Vega magnitudes. The row selection criteria for each instrument/mode are:

  • FGS:

    • Detector

  • MIRI:

    • Filter

  • NIRCam:

    • Filter and Pupil

  • NIRISS:

    • Filter and Pupil

PARS-SOURCECATALOGSTEP Parameter Reference File

REFTYPE

PARS-SOURCECATALOGSTEP

Data model

N/A

Reference Selection Keywords

CRDS selects appropriate pars-sourcecatalogstep references based on the following keywords.

Instrument

Keywords

FGS

EXP_TYPE

MIRI

EXP_TYPE, FILTER

NIRCAM

EXP_TYPE, FILTER

NIRISS

EXP_TYPE, FILTER

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