Reference Files

The cube_build step uses CUBEPAR reference file.

CUBEPAR reference file

REFTYPE:

CUBEPAR

Data models:

MiriIFUCubeParsModel, NirspecIFUCubeParsModel

The CUBEPAR reference file contains parameter values used to construct the output IFU cubes.

Reference Selection Keywords for CUBEPAR

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

Instrument

Keywords

MIRI

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

NIRSPEC

INSTRUME, EXP_TYPE, 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 CUBEPAR

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

Keyword

Data Model Name

EXP_TYPE

model.meta.exposure.type

MIRI Reference File Format

The MIRI CUBEPAR reference files are FITS format, with 5 BINTABLE extensions. The FITS primary data array is assumed to be empty. The format and content of the MIRI CUBEPAR reference file

EXTNAME

XTENSION

Dimensions

CUBEPAR

BINTABLE

TFIELDS = 6

CUBEPAR_MSM

BINTABLE

TFIELDS = 6

MULTICHANNEL_MSM

BINTABLE

TFIELDS = 5

CUBEPAR_EMSM

BINTABLE

TFIELDS = 5

MULTICHANNEL_EMSM

BINTABLE

TFIELDS = 4

MULTICHANNEL_DRIZ

BINTABLE

TFIELDS = 1

NIRSPec Reference File Format

The NIRSpec CUBEPAR reference files are FITS format, with 9 BINTABLE extensions.

EXTNAME

XTENSION

Dimensions

CUBEPAR

BINTABLE

TFIELDS = 6

CUBEPAR_MSM

BINTABLE

TFIELDS = 6

MULTICHAN_PRISM_MSM

BINTABLE

TFIELDS = 5

MULTICHAN_MED_MSM

BINTABLE

TFIELDS = 5

MULTICHAN_HIGH_MSM

BINTABLE

TFIELDS = 5

CUBEPAR_EMSM

BINTABLE

TFIELDS = 5

MULTICHAN_PRISM_EMSM

BINTABLE

TFIELDS = 4

MULTICHAN_MED_EMSM

BINTABLE

TFIELDS = 4

MULTICHAN_HIGH_EMSM

BINTABLE

TFIELDS = 4

The formats of the individual table extensions are listed below, first for the MIRI reference file and then for NIRSpec.

Table

Column

Data type

Units

CUBEPAR

CHANNEL

shortint

N/A

BAND

ch*6

N/A

WAVEMIN

float

microns

WAVEMAX

float

microns

SPAXELSIZE

float

arcseconds

SPECTRALSTEP

double

microns

CUBEPAR_MSM

CHANNEL

shortint

N/A

BAND

ch*6

N/A

ROISPATIAL

float

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

MULTICHANNEL_MSM

WAVELENGTH

double

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

CUBEPAR_EMSM

CHANNEL

shortint

N/A

BAND

ch*6

N/A

ROISPATIAL

float

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

MULTICHANNEL_EMSM

WAVELENGTH

double

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

MULTICHANNEL_DRIZ

WAVELENGTH

double

microns

Table

Column

Data type

Units

CUBEPAR

DISPERSER

ch*5

N/A

FILTER

ch*6

N/A

WAVEMIN

double

microns

WAVEMAX

double

microns

SPAXELSIZE

double

arcseconds

SPECTRALSTEP

double

microns

CUBEPAR_MSM

DISPERSER

ch*5

N/A

FILTER

ch*6

N/A

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

MULTICHAN_PRISM_MSM

WAVELENGTH

double

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

MULTICHAN_MED_MSM

WAVELENGTH

float

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

MULTICHAN_HIGH_MSM

WAVELENGTH

float

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

POWER

double

unitless

SOFTRAD

double

unitless

CUBEPAR_EMSM

DISPERSER

ch*5

N/A

FILTER

ch*6

N/A

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

MULTICHAN_PRISM_EMSM

WAVELENGTH

double

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

MULTICHAN_MED_EMSM

WAVELENGTH

float

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

MULTICHAN_HIGH_EMSM

WAVELENGTH

float

microns

ROISPATIAL

double

arcseconds

ROISPECTRAL

double

microns

SCALERAD

double

unitless

These reference files contain tables for each wavelength band giving the spatial and spectral size, and the size of the region of interest (ROI) to use to construct an IFU cube. If only one band is used to construct the IFU cube then the CUBEPAR and CUBEPAR_MSM or CUBE_EMSM tables are used. These types of cubes will have a linear - wavelength dimension. If more than one wavelength band is used to build the IFU cube then the MULTICHANNEL (MIRI) or MULTICHAN (NIRSPEC) tables are used o set the spectral and spatial roi size, and the wavelength dependent weighting function parameters. For multi-band IFU cubes then the final spatial size will be the smallest one from the list of input bands and these cubes will have a non-linear wavelength dimension.

The MIRI reference table descriptions:

  • CUBEPAR table contains the spatial and spectral cube sample size for each band.

  • CUBEPAR_MSM table contains the Modified Shepard Method (MSM) weighting values to use for each band.

  • MULTICHANNEL_MSM table is used for the MSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from several bands and the final output is to have an IFU cube of varying spectral scale.

  • CUBEPAR_EMSM table contains the Exponential Modified Shepard Method (EMSM) weighting values to use for each band.

  • MULTICHANNEL_EMSM table is used for the EMSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from several bands and the final output is to have an IFU cube of varying spectral scale.

  • MULTICHANNEL_DRIZ table is used for the DRIZZLE weighting and contains the wavelengths to use when IFU cubes are created from several bands and the final output is to have an IFU cube of varying spectral scale.

The NIRSPEC reference table descriptions:

  • CUBEPAR table contains the spatial and spectral cube sample size for each band.

  • CUBEPAR_MSM table contains the Modified Shepard Method (MSM) weighting values to use for each band.

  • MULTICHAN_PRISM_MSM table is used for the MSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the grating prism and the final IFU Cube output has a varying spectral scale.

  • MULTICHAN_MED_MSM table is used for the MSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the medium resolution grating and the final IFU Cube output has a varying spectral scale.

  • MULTICHAN_HIGH_MSM table is used for the MSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the high resolution gratings and the final IFU Cube output has a varying spectral scale.

  • CUBEPAR_EMSM table contains the Exponential Modified Shepard Method (EMSM) weighting values to use for each band.

  • MULTICHAN_PRISM_EMSM table is used for the EMSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the grating prism and the final IFU Cube output has a varying spectral scale.

  • MULTICHAN_MED_EMSM table is used for the EMSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the medium resolution grating and the final IFU Cube output has a varying spectral scale.

  • MULTICHAN_HIGH_EMSM table is used for the EMSM weighting and contains the wavelengths and associated region of interest size to use when IFU cubes are created from the high resolution gratings and the final IFU Cube output has a varying spectral scale.