Reference File

There are two types of reference files used by the cube_build step. The first type holds the default cube parameters used in setting up the output IFU Cube. The reftype for this reference file is cubepars and there is a reference file of this type for MIRI data and one for NIRSPEC data. These files contain tables for each band of the spatial and spectral size and the size of the region of interest to use to construct the IFU cube. If more than one band is used to build the IFU cube, then the final spatial and spectral size will be the smallest one from the list of input bands. Currently cube_build can only produce IFU cubes with a linear spatial and spectral dimension. In the future we plan to allow a varying spectral step with wavelength.

The other type of reference file pertains only to MIRI data and contains the width of the PSF and LSF per band. The reftype for this reference file is resol. This information is used if the weight function incorporates the size of the psf and lsf, i.e. –weighting = miripsf

CRDS Selection Criteria

The cube parameter reference file selection is based on Instrument. CRDS selection criteria for the MIRI resolution reference file is also based on Instrument (a N/Q is returned for NIRSPEC data).

Cube Building Parameter Reference File Format

The cube parameter reference files are FITS files with BINTABLE extensions. The FITS primary data array is assumed to be empty. The MIRI cube parameter file contains three BINTABLE extensions, while the NIRSPEC file contains five BINTABLE extensions. In both files the first extension contains the spatial and spectral cube sample size for each band. The second extension holds the Modified Shepard weighting values to use for each band. The third extension will be used in Build 7.2 and contains the wavelengths and associated region of interest size to use if the IFU cubes are created from several bands and the final output is to have an IFU cube of varying spectral scale. In the case of MIRI the twelve spectral bands can be combined into a single IFU cube an all the information to create cubes of varying wavelength sampling is contained in this third BINTABLE extension. However for NIRSPEC data there are three types of multi-band cubes: PRISM, MEDIUM and HIGH resolution. The third, forth and fifth BINTABLE extensions in the NIRSPEC reference file contains the wavelength sampling and region of interest size to use for PRISM, MEDIUM resolution, and HIGH resolution multi-band cubes, respectively.

MIRI Resolution reference file

The MIRI resolution reference file is a FITS file with four BINTABLE extensions. The FITS primary data array is assumed to be empty. The first BINTABLE extension contains the RESOLVING_POWER the information to use for each band. This table has 12 rows and 11 columns, one row of information for each band. The parameters in the 11 columns provide the polynomial coefficients to determine the resolving power for band that row corresponds to. The second BINTABLE extension, PSF_FWHM_ALPHA, has a format of 1 row and 5 columns. The 5 columns hold the polynomial coefficients for determining the alpha PSF size. The third BINTABLE extension, PSF_FWHM_BETA, has a format of 1 row and 5 columns. The 5 columns hold the polynomial coefficients for determining the beta PSF size.