Reference Files

WCS Reference files are in the Advanced Scientific Data Format (ASDF). The best way to create the file is to programmatically create the model and then save it to a file. A tutorial on creating reference files in ASDF format is available at:

https://github.com/spacetelescope/jwreftools/blob/master/docs/notebooks/referece_files_asdf.ipynb

Transforms are 0-based. The forward direction is from detector to sky.

Reference file types used by assign_wcs

REFTYPE

Description

Instruments

CAMERA

NIRSpec Camera model

NIRSpec

COLLIMATOR

NIRSpec Collimator Model

NIRSpec

DISPERSER

Disperser parameters

NIRSpec

DISTORTION

Spatial distortion model

FGS, MIRI, NIRCam, NIRISS

FILTEROFFSET

MIRI Imager fiter offsets

MIRI

FORE

Transform through the NIRSpec FORE optics

NIRSpec

FPA

Transform in the NIRSpec FPA plane

NIRSpec

IFUFORE

Transform from the IFU slicer to the IFU entrance

NIRSpec

IFUPOST

Transform from the IFU slicer to the back of the IFU

NIRSpec

IFUSLICER

IFU Slicer geometric description

NIRSpec

MSA

Transformin the NIRSpec MSA plane

NIRSpec

OTE

Transform through the Optical Telescope Element

NIRSpec

SPECWCS

Wavelength calibration models

MIRI, NIRCam, NIRISS

REGIONS

Stores location of the regions on the detector

MIRI

WAVELENGTHRANGE

Typical wavelength ranges

MIRI, NIRCam, NIRISS, NIRSpec