wfss

jwst.assign_wcs.niriss.wfss(input_model, reference_files)

Create the WCS pipeline for a NIRISS grism observation.

Parameters:

• input_model (jwst.datamodels.ImagingModel) – The input datamodel, derived from datamodels
• reference_files (dict) – Dictionary specifying reference file names

Notes

reference_files = {

“specwcs”: ‘GR150C_F090W.asdf’ “distortion”: ‘NRCA1_FULL_distortion.asdf’ }

The tree in the grism reference file has a section for each order/beam as well as the link to the filter data file, not sure if there will be a separate passband reference file needed for the wavelength scaling or the wedge offsets. This file is currently created in jwreftools/niriss/niriss_reftools.

The direct image the catalog has been created from was corrected for distortion, but the dispersed images have not. This is OK if the trace and dispersion solutions are defined with respect to the distortion-corrected image. The catalog from the combined direct image has object locations in in detector space and the RA DEC of the object on sky.

The WCS information for the grism image plus the observed filter will be used to translate these to pixel locations for each of the objects. The grism images will then use their grism trace information to translate to detector space. The translation is assumed to be one-to-one for purposes of identifying the center of the object trace.

The extent of the trace for each object can then be calculated based on the grism in use (row or column). Where the left/bottom of the trace starts at t = 0 and the right/top of the trace ends at t = 1, as long as they have been defined as such by th team.

The extraction box is calculated to be the minimum bounding box of the object extent in the segmentation map associated with the direct image. The values of the min and max corners are saved in the photometry catalog in units of RA,DEC so they can be translated to pixels by the dispersed image’s imaging wcs.

The sensitivity information from the original aXe style configuration file needs to be modified by the passband of the filter used for the direct image to get the min and max wavelengths which correspond to t=0 and t=1, this currently has been done by the team and the min and max wavelengths to use to calculate t are stored in the grism reference file as wrange, which can be selected by wrange_selector which contains the filter names.

Source catalog use moved to extract_2d.