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, 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

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.