FILTEROFFSET Reference File

REFTYPE:

FILTEROFFSET

Data model:

FilteroffsetModel

Reference Selection Keywords for FILTEROFFSET

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

Instrument	Keywords
MIRI	INSTRUME, DETECTOR, EXP_TYPE, DATE-OBS, TIME-OBS
NIRCam	INSTRUME, CHANNEL, MODULE, DATE-OBS, TIME-OBS
NIRISS	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 filteroffset reference file is an ASDF file that contains a list called filters. Every item in the list contains one or more entries that are used as selectors, as well as the column and row offset values to be applied. For the MIRI instrument, there is one selector “filter”, which is the name of the filter to which the offsets apply. For NIRCam and NIRISS, the selectors are “filter” and “pupil”.

The offsets, in units of pixels, are added to positions in images that use the reference filter/pupil, in order to align images to the reference filter/pupil frame.

filters:

filter:

Filter name

pupil:

Pupil name (NIRCam and NIRISS only)

column_offset:

Offset in x (in pixels)

row_offset:

Offset in y (in pixels)