Reference Files

The emicorr step can use an EMI reference file.

EMICORR Reference File

REFTYPE:

EMICORR

Data model:

EmiModel

The EMICORR reference file contains data necessary for removing contaminating MIRI EMI frequencies.

Reference Selection Keywords for EMICORR

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

Instrument	Keywords
MIRI	INSTRUME, DATE-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

EMICORR Reference File Format

MIRI EMICORR reference files are in ASDF format. The EMICORR reference file contains the frequencies for which the image will be corrected. Example file contents:

root (AsdfObject)
  ├─frequencies (dict)
    │ ├─Hz10 (dict)
    │ │ ├─frequency (float): 10.039216
    │ │ └─phase_amplitudes (NDArrayType): shape=(500,), dtype=float32
    │ ├─Hz10_slow_MIRIFULONG (dict)
    │ │ ├─frequency (float): 10.039216
    │ │ └─phase_amplitudes (NDArrayType): shape=(250,), dtype=float32
  └─subarray_cases (dict)
    ├─BRIGHTSKY (dict)
    │ ├─frameclocks (int): 23968
    │ ├─freqs (dict)
    │ │ ├─FAST (list)
    │ │ │ └─[0] (str): Hz10
    │ │ └─SLOW (dict)
    │ │   ├─MIRIFULONG (list)
    │ │   │ └─[0] (str): Hz10_slow_MIRIFULONG
    │ │   ├─MIRIFUSHORT (list)
    │ │   │ └─[0] (str): Hz10_slow_MIRIFUSHORT
    │ │   └─MIRIMAGE (list)
    │ │     └─[0] (str): Hz10_slow_MIRIMAGE
    │ └─rowclocks (int): 82
    ├─MASK1140 (dict)
    │ ├─frameclocks (int): 23968
    │ ├─freqs (dict)
    │ │ ├─FAST (list)
    │ │ │ ├─[0] (str): Hz390
    │ │ │ └─[1] (str): Hz10
    │ │ └─SLOW (dict)
    │ │   ├─MIRIFULONG (list)
    │ │   │ ├─[0] (str): Hz390
    │ │   │ └─[1] (str): Hz10_slow_MIRIFULONG
    │ │   ├─MIRIFUSHORT (list)
    │ │   │ ├─[0] (str): Hz390
    │ │   │ └─[1] (str): Hz10_slow_MIRIFUSHORT
    │ │   └─MIRIMAGE (list)
    │ │     ├─[0] (str): Hz390
    │ └─rowclocks (int): 82

Frequency Selection

The frequency to be corrected for will be selected according to the dictionary contained in the key subarray_cases in the reference file. This contains the subarray names and the names of the corresponding frequencies to be used in the correction.