Reference Files¶
The extract_2d
step uses the WAVELENGTHRANGE reference file.
The WAVELENGTHRANGE reference file is only used for NIRCam and NIRISS
Wide-Field Slitless Spectroscopy (WFSS) exposures.
WAVELENGTHRANGE Reference File¶
- REFTYPE
WAVELENGTHRANGE
- Data model
The WAVELENGTHRANGE reference file contains information on the minimum and
maximum wavelengths of various spectroscopic modes, which can be
order-dependent. The reference data are used to construct bounding boxes
around the spectral traces produced by each object in the NIRCam and NIRISS
WFSS modes.
If a list of GrismObject
is supplied, then no reference file is necessary.
Reference Selection Keywords for WAVELENGTHRANGE¶
CRDS selects appropriate WAVELENGTHRANGE references based on the following keywords. WAVELENGTHRANGE is not applicable for instruments not in the table. All keywords used for file selection are required.
Instrument |
Keywords |
---|---|
MIRI |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
NIRCam |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
NIRISS |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
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
Type Specific Keywords for WAVELENGTHRANGE¶
In addition to the standard reference file keywords listed above, the following keywords are required in WAVELENGTHRANGE reference files
Keyword |
Data Model Name |
---|---|
EXP_TYPE |
model.meta.exposure.type |
These keywords are used as CRDS selectors
Reference Selection Keywords for WAVELENGTHRANGE¶
CRDS selects appropriate WAVELENGTHRANGE references based on the following keywords. WAVELENGTHRANGE is not applicable for instruments not in the table. All keywords used for file selection are required.
Instrument |
Keywords |
---|---|
MIRI |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
NIRCam |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
NIRISS |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
NIRSpec |
INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS |
Reference File Format¶
WAVELENGTHRANGE reference files are in ASDF format, with the format and contents
specified by the WavelengthrangeModel
data model schema.
The exact content varies a bit depending on instrument mode, as explained in the
following sections.
MIRI MRS¶
For MIRI MRS, the WAVELENGTHRANGE file consists of two fields that define the wavelength range for each combination of channel and band.
- channels
An ordered list of all possible channel and band combinations for MIRI MRS, e.g. “1SHORT”.
- wavelengthrange
An ordered list of (lambda_min, lambda_max) for each item in the list above
NIRSpec¶
For NIRSpec, the WAVELENGTHRANGE file is a dictionary storing information about default wavelength range and spectral order for each combination of filter and grating.
- filter_grating
- order
Default spectral order
- range
Default wavelength range
NIRCam WFSS, NIRCam TSGRISM, NIRISS WFSS¶
For NIRCam WFSS and TSGRIM modes, as well as NIRISS WFSS mode, the WAVELENGTHRANGE reference file contains the wavelength limits to use when calculating the minimum and maximum dispersion extents on the detector. It also contains the default list of orders that should be extracted for each filter. To be consistent with other modes, and for convenience, it also lists the orders and filters that are valid with the file.
- order
A list of orders this file covers
- wavelengthrange
A list containing the list of [order, filter, wavelength min, wavelength max]
- waverange_selector
The list of FILTER names available
- extract_orders
A list containing the list of orders to extract for each filter