IFUPOST Reference File (NIRSpec only)

REFTYPE

IFUPOST

Data model

IFUPostModel

Reference Selection Keywords for IFUPOST

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

Instrument

Keywords

NIRSpec

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

Reference File Format

The IFUPOST reference file provides the parameters (Paraxial and distortions coefficients) for the coordinate transforms from the slicer plane to the MSA plane (out), that is the plane of the IFU virtual slits.

The reference file contains models made up based on an offset and a polynomial. There is a model for each of the slits and is indexed by the slit number. The models is used as part of the conversion from the GWA to slit.

slice_<slice_number>
model

Polynomial and rotation models.