Description¶
- Class:
jwst.ami.AmiAnalyzeStep
- Alias:
ami_analyze
The ami_analyze
step is one of the AMI-specific steps in the ami
sub-package that is part of Stage 3 calwebb_ami3
processing. It applies the Lacour-Greenbaum (LG) image plane
modeling algorithm to a NIRISS AMI image.
The routine computes a number of parameters, including a model fit (and
residuals) to the image, fringe amplitudes and phases, and closure phases
and amplitudes.
The JWST AMI observing template allows for exposures to be obtained using
either full-frame (SUBARRAY=”FULL”) or subarray (SUBARRAY=”SUB80”) readouts.
When processing a full-frame exposure, the ami_analyze
step extracts
and processes a region from the image corresponding to the size and location of
the SUB80 subarray, in order to reduce execution time.
Arguments¶
The ami_analyze
step has four optional arguments:
- –oversample:
The oversampling factor to be used in the model fit (default=3).
- –rotation:
Initial guess for the rotation of the PSF in the input image, in units of degrees (default=0.0).
- –psf_offset:
List of PSF offset values to use when creating the model array (default=’0.0 0.0’).
- –rotation_search:
List of start, stop, and step values that define the list of rotation search values. The default setting of ‘-3 3 1’ results in search values of [-3, -2, -1, 0, 1, 2, 3].
Inputs¶
2D calibrated image¶
- Data model:
- File suffix:
_cal
The ami_analyze
step takes a single calibrated image as input, which should be
the “_cal” product resulting from calwebb_image2 processing.
Multiple exposures can be processed via use of an ASN file that is used as input
to the calwebb_ami3 pipeline. The ami_analyze
step itself does
not accept an ASN as input.
Outputs¶
LG model parameters¶
- Data model:
- File suffix:
_ami
The ami_analyze
step produces a single output file, containing the
following list of extensions:
FIT
: a 2D image of the fitted modelRESID
: a 2D image of the fit residualsCLOSURE_AMP
: table of closure amplitudesCLOSURE_PHA
: table of closure phasesFRINGE_AMP
: table of fringe amplitudesFRINGE_PHA
: table of fringe phasesPUPIL_PHA
: table of pupil phasesSOLNS
: table of fringe coefficients
The output file name syntax is exposure-based, using the input file name as the root, with the addition of the association candidate ID and the “_ami” product type suffix, e.g. “jw87600027001_02101_00002_nis_a3001_ami.fits.”
Reference Files¶
The ami_analyze
step uses a THROUGHPUT reference file.
THROUGHPUT Reference File¶
- REFTYPE:
THROUGHPUT
- Data model:
The THROUGHPUT reference file contains throughput data for the filter used in the AMI image.
Reference Selection Keywords for THROUGHPUT¶
CRDS selects appropriate THROUGHPUT references based on the following keywords. THROUGHPUT is not applicable for instruments not in the table. All keywords used for file selection are required.
Instrument |
Keywords |
---|---|
NIRISS |
INSTRUME, FILTER, 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 THROUGHPUT¶
In addition to the standard reference file keywords listed above, the following keywords are required in THROUGHPUT reference files, because they are used as CRDS selectors (see Reference Selection Keywords for THROUGHPUT):
Keyword |
Data Model Name |
---|---|
FILTER |
model.meta.instrument.filter |
Reference File Format¶
THROUGHPUT reference files are FITS files with one BINTABLE extension. The FITS primary data array is assumed to be empty. The format of the file is as follows:
EXTNAME |
XTENSION |
NAXIS |
Dimensions |
Data type |
---|---|---|---|---|
THROUGHPUT |
BINTABLE |
2 |
TFIELDS = 2 |
N/A |
The table extension contains two columns, giving wavelength and throughput values for a particular filter:
Column name |
Data type |
Units |
---|---|---|
wavelength |
float |
Angstroms |
throughput |
float |
(unitless) |