implement pixelscale switching for MRS sims

webbpsf/tests/test_miri.py

@@ -96,28 +96,37 @@ def test_miri_nonsquare_detector():
     assert miri.detector_position == (1023, 1031)
 
 def test_mode_switch():
+    """Test switching between imaging and IFU modes, and switching IFU bands
+    Also checks this works to switch aperturenane, and conversely setting aperturename switches mode if needed.
+    Also checks that this automatically changes the rotation and pixelscale properties, as expected.
+    """
     miri = webbpsf_core.MIRI()
     imager_rotation = miri._rotation
+    imager_pixscale = miri.pixelscale
 
     # Explicitly switch mode to IFU
     miri.mode = 'IFU'
     assert 'IFU' in miri.aperturename
     assert miri.detector =='MIRIFUSHORT'
     assert miri.aperturename.startswith('MIRIFU_CH')
     assert miri._rotation != imager_rotation
+    assert miri.pixelscale > imager_pixelscale
     # Explicitly switch back to imaging
     miri.mode = 'imaging'
     assert 'IFU' not in miri.aperturename
     assert miri.detector =='MIRIM'
     assert miri.aperturename.startswith('MIRIM_')
     assert miri._rotation == imager_rotation
+    assert miri.pixelscale == imager_pixelscale
+
 
     # Implicitly switch to IFU 
     miri.set_position_from_aperture_name('MIRIFU_CHANNEL3B')
     assert 'IFU' in miri.aperturename
     assert miri.detector =='MIRIFULONG'
     assert miri.aperturename == 'MIRIFU_CHANNEL3B'
     assert miri._rotation != imager_rotation
+    assert miri.pixelscale > imager_pixelscale
 
     # implicitly switch to imaging
     # LRS is an odd case, SLIT aper type but operates like in imaging mode
@@ -126,19 +135,37 @@ def test_mode_switch():
     assert miri.detector =='MIRIM'
     assert miri.aperturename.startswith('MIRIM_')
     assert miri._rotation == imager_rotation
+    assert miri.pixelscale == imager_pixelscale
 
     # And back to IFU again:
     miri.mode = 'IFU'
     assert 'IFU' in miri.aperturename
     assert miri.detector =='MIRIFUSHORT'
     assert miri.aperturename.startswith('MIRIFU_CH')
     assert miri._rotation != imager_rotation
+    assert miri.pixelscale > imager_pixelscale
 
     # band switching should toggle detector and aper name
     miri.band = '4C'
     assert miri.detector == 'MIRIFULONG'
     assert miri.aperturename == 'MIRIFU_CHANNEL4C'
+    assert miri.pixelscale > 3*imager_pixelscale
 
     miri.band = '2A'
     assert miri.detector == 'MIRIFUSHORT'
     assert miri.aperturename == 'MIRIFU_CHANNEL2A'
+    assert imager_pixelscale < miri.pixelscale < 2*imager_pixelscale
+
+def test_IFU_wavelengths():
+    """ Test computing the wqvelength sampling for a sim IFU cube """
+    miri = webbpsf_core.MIRI()
+    # check mode swith to IFU
+    miri.mode = 'IFU'
+    miri.band = '2A'
+    waves = miri.get_IFU_wavelengths()
+    assert isinstance(waves, u.Quantity)
+
+    assert len(waves) > 900  # there are lots of wavelengths in MRScubes
+    # and test we can specify a reduced wavelength sampling:
+    for n in (10, 100):
+        assert len(miri.get_IFU_wavelengths(n)) == n

webbpsf/tests/test_nirspec.py

@@ -52,17 +52,33 @@ def test_calc_datacube_fast():
 
 
 def test_mode_switch():
+    """ Test switch between IFU and imaging modes """
     nrs = webbpsf_core.NIRSpec()
     # check mode swith to IFU
     nrs.mode = 'IFU'
     assert 'IFU' in nrs.aperturename
     assert nrs.band == 'PRISM/CLEAR'
 
     # check switch of which IFU band
-    nrs.grating = 'G395H'
+    nrs.disperser = 'G395H'
     nrs.filter = 'F290LP'
     assert nrs.band == 'G395H/F290LP'
 
     # check mode switch back to imaging
     nrs.mode = 'imaging'
     assert 'IFU' not in nrs.aperturename
+
+def test_IFU_wavelengths():
+    """ Test computing the wqvelength sampling for a sim IFU cube """
+    nrs = webbpsf_core.NIRSpec()
+    # check mode swith to IFU
+    nrs.mode = 'IFU'
+    nrs.disperser = 'G235H'
+    nrs.filter = 'F170LP'
+    waves = nrs.get_IFU_wavelengths()
+    assert isinstance(waves, u.Quantity)
+
+    assert len(waves) > 3000  # there are lots of wavelengths in the high-resolution grating cubes
+    # and test we can specify a reduced wavelength sampling:
+    for n in (10, 100):
+        assert len(nrs.get_IFU_wavelengths(n)) == n

webbpsf/webbpsf_core.py

@@ -960,6 +960,9 @@ def aperturename(self, value):
                 self._aperturename = value
                 # Update DetectorGeometry class
                 self._detector_geom_info = DetectorGeometry(self.siaf, self._aperturename)
+                if not has_custom_pixelscale:
+                    self.pixelscale = self._get_pixelscale_from_apername(value)
+                    _log.debug( f"Pixelscale updated to {self.pixelscale} based on IFU cubepars for {value}")
 
             else:
                 if self.detector not in value:
@@ -2177,8 +2180,12 @@ def _get_pixelscale_from_apername(self, apername):
         """Simple utility function to look up pixelscale from apername"""
 
         if 'MIRIFU' in apername:
-            print('special case for MIRI IFU pixelscales')
-            return 0.1
+            if apername.startswith('MIRIFU_CHANNEL'):
+                band = apername[-2:]
+                spaxelsize, _, _, _= self._IFU_bands_cubepars[band]
+                return spaxelsize
+            else:
+                raise RuntimeError(f"Not sure how to determine pixelscale for {apername}")
         else:
             return super()._get_pixelscale_from_apername(apername)
 
@@ -2252,7 +2259,6 @@ def band(self, value):
         if value in self._IFU_bands_cubepars.keys():
             self._band = value
             #self._slice_width = self._IFU_pixelscale[f"Ch{self._band[0]}"][0]
-
             self.aperturename = 'MIRIFU_CHANNEL' + value
             # setting aperturename will also auto update self._rotation
             #self._rotation = self.MRS_rotation[self._band]
@@ -2973,7 +2979,6 @@ def _tel_coords(self):
     def _get_pixelscale_from_apername(self, apername):
         """Simple utility function to look up pixelscale from apername"""
         if 'IFU' in apername:
-            print('DEBUG - special case for NIRSpec IFU pixelscales')
             return super()._get_pixelscale_from_apername('NRS1_FULL')
         else:
             return super()._get_pixelscale_from_apername(apername)