Reference Files

The picture_frame step uses a PICTUREFRAME reference file.

PICTUREFRAME Reference File

REFTYPE:

PICTUREFRAME

Data model:

PictureFrameModel

The PICTUREFRAME reference file contains data necessary for removing thermal artifacts (the “picture frame” effect) from NIRSpec exposures.

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

PICTUREFRAME Reference File Format

NIRSpec PICTUREFRAME reference files are in FITS format with one image extension. The primary HDU does not contain a data array. The format and content of the file is as follows:

EXTNAME	XTENSION	NAXIS	Dimensions	Data type
SCI	IMAGE	2	2048 x 2048	float

The values in the SCI array give rate values for the thermal background artifact in full frame exposures. The reference image is intended to be scaled and offset before subtraction from science exposure images.