IFUSLICER Reference File (NIRSpec only)

REFTYPE

IFUSLICER

Data model

IFUSlicerModel

Reference Selection Keywords for IFUSLICER

CRDS selects appropriate IFUSLICER references based on the following keywords. IFUSLICER 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 IFUSLICER stores information about the metrology of the IFU slicer - relative positioning and size of the aperture of each individual slicer and the absolute reference with respect to the center of the field of view. The reference file contains two fields - “data” and “model”. The “data” field is an array with 30 rows pertaining to the 30 slices and the columns are

data

Array with reference data for each slicer. It has 5 columns

NO

Slice number (0 - 29)

x_center

X coordinate of the center (in meters)

y_center

Y coordinate of the center (in meters)

x_size

X size of teh aperture (in meters)

y_size

Y size of the aperture (in meters)

model

Transform from relative positions within the IFU slicer to absolute positions within the field of view. It’s a combination of shifts and rotation.