FPA Reference File (NIRSpec only)

REFTYPE

FPA

Data model

FPAModel

Reference Selection Keywords for FPA

CRDS selects appropriate FPA references based on the following keywords. FPA 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 FPA reference file stores information on the metrology of the Focal Plane Assembly (FPA), which consists of two Sensor Chip Arrays (SCA), named NRS1 and NRS2.

The reference file contains two fields : “nrs1_model” and “nrs2_model”. Each of them stores the transform (shift and rotation) to transform positions from the FPA to the respective SCA. The output units are in pixels.

nrs1_model

Transform for the NRS1 detector.

nrs2_model

Transform for the NRS2 detector.