Reference Files

The flat_field step uses a FLAT reference file.

FLAT Reference File

REFTYPE:

FLAT

Data model:

roman_datamodels.datamodels.FlatRefModel

The FLAT reference file contains pixel-by-pixel detector response values. It is used.

Reference Selection Keywords for FLAT

CRDS selects appropriate FLAT references based on the following attributes. FLAT is not applicable for instruments not in the table. Non-standard attributes used for file selection are required.

Instrument

Metadata

WFI

instrument, detector, optical_element, date, time

Standard ASDF metadata

The following table lists the attributes that are required to be present in all reference files. The first column shows the attribute in the ASDF reference file headers, which is the same as the name within the data model meta tree (second column). The second column gives the roman data model name for each attribute, which is useful when using data models in creating and populating a new reference file.

Attribute

Fully Qualified Path

author

model.meta.author

model_type

model.meta.model_type

date

model.meta.date

description

model.meta.description

instrument

model.meta.instrument.name

reftype

model.meta.reftype

telescope

model.meta.telescope

useafter

model.meta.useafter

NOTE: More information on standard required attributes can be found here: Standard ASDF metadata

Type Specific Keywords for FLAT

In addition to the standard reference file attributes listed above, the following attributes are required in FLAT reference files, because they are used as CRDS selectors (see Reference Selection Keywords for FLAT):

Attribute

Fully qualified path

Instruments

detector

model.meta.instrument.detector

WFI

exptype

model.meta.exposure.type

optical_element

model.meta.instrument.optical_element

Reference File Format

FLAT reference files are ASDF format, with 3 data arrays. The format and content of the file is as follows:

Data

Array Type

Dimensions

Data type

data

NDArray

4096 x 4096

float32

err

NDArray

4096 x 4096

float32

dq

NDArray

4096 x 4096

uint32

The ASDF file contains a single set of data, err, and dq arrays.