Avoid adding detector IPC to MIRI MRS IFU sims. Improve testing rigor…

… & consistency

stpsf/detectors.py

@@ -581,7 +581,9 @@ def apply_miri_ifu_broadening(hdulist, options, slice_width=0.196):
     model_type = options.get('ifu_broadening', 'empirical_cruciform')
 
     if model_type is None or model_type.lower() == 'none':
+        webbpsf.webbpsf_core._log.debug('MIRI MRS: IFU broadening option is set to None, skipping IFU PSF broadening effects.')
         return hdulist
+    webbpsf.webbpsf_core._log.debug('MIRI MRS: Adding IFU PSF broadening effects.')
 
     ext = 1  # Apply this effect to the OVERDIST extension, which at this point in the code will be ext 1
 

stpsf/stpsf_core.py

@@ -1147,6 +1147,12 @@ def _get_pixelscale_from_apername(self, apername):
         # The slight departures from this are handled in the distortion model; see distortion.py
         return (ap.XSciScale + ap.YSciScale) / 2
 
+    @property
+    def mode(self):
+        # This exists just for API consistency with the subclasses that have an imaging vs IFU mode toggle,
+        # so that all JWST instrument classes have a mode attribute, consistently, whether used or not
+        return "imaging"
+
     def _get_fits_header(self, result, options):
         """populate FITS Header keywords"""
         super(JWInstrument, self)._get_fits_header(result, options)
@@ -1252,7 +1258,9 @@ def _calc_psf_format_output(self, result, options):
         add_distortion = options.get('add_distortion', True)
         crop_psf = options.get('crop_psf', True)
         # you can turn on/off IPC corrections via the add_ipc option, default True.
-        add_ipc = options.get('add_ipc', True)
+        # except for IFU mode simulations, it doesn't make sense to add the regular detector IPC
+        # instead the more complex IFU broadening models should be applied
+        add_ipc = options.get('add_ipc', True if self.mode != 'IFU' else False)
 
         # Add distortion if set in calc_psf
         if add_distortion:

stpsf/tests/test_miri.py

@@ -245,17 +245,17 @@ def test_miri_ifu_broadening():
 
     # test flux conservation. THis is close but not exact, due to the optical distortion part which is distinct from but
     # happens at same point in the calculation as the IFU broadening effect.
-    assert np.isclose(psf['DET_SAMP'].data.sum(), psf['DET_DIST'].data.sum(), rtol=2e-4), "IFU broadening should not change total flux much"
+    assert np.isclose(psf['DET_SAMP'].data.sum(), psf['DET_DIST'].data.sum()), "IFU broadening should not change total flux much"
 
 
     # Now test that we can also optionally turn off that effect
     miri.options['ifu_broadening'] = None
-    psf_nb = miri.calc_psf(monochromatic=2.8e-6, fov_pixels=10)
+    psf_nb = miri.calc_psf(monochromatic=6.8e-6, fov_pixels=20)
 
     fwhm_oversamp = stpsf.measure_fwhm(psf_nb, ext='OVERSAMP')
     fwhm_overdist = stpsf.measure_fwhm(psf_nb, ext='OVERDIST')
     # The PSF will still be a little broader in this case due to the IPC model, but not by a lot..
-    assert fwhm_oversamp < fwhm_overdist <= 1.1 * fwhm_oversamp, "IFU broadening model should be disabled for this test case"
+    assert fwhm_overdist == fwhm_oversamp, "IFU broadening model should be disabled for this test case"
 
     # test flux conservation with and without the IFU broadening. This should be a more exact match
     assert np.isclose(psf_nb['DET_DIST'].data.sum(), psf['DET_DIST'].data.sum() ), "IFU broadening should not change total flux much"