Merge pull request #897 from mperrin/enhance_868_nrs_aper_pas

Update NIRSpec aperture PAs

webbpsf/tests/test_nirspec.py

@@ -61,11 +61,13 @@ def test_calc_datacube_fast():
 def test_mode_switch():
     """Test switch between IFU and imaging modes"""
     nrs = webbpsf_core.NIRSpec()
+    nrs_default_v3pa = nrs._rotation
     # check mode swith to IFU
     nrs.mode = 'IFU'
     assert 'IFU' in nrs.aperturename
     assert nrs.band == 'PRISM/CLEAR'
     assert nrs.image_mask is None
+    assert nrs._rotation != nrs_default_v3pa
 
     # check switch of which IFU band
     nrs.disperser = 'G395H'
@@ -75,6 +77,7 @@ def test_mode_switch():
     # check mode switch back to imaging
     nrs.mode = 'imaging'
     assert 'IFU' not in nrs.aperturename
+    assert nrs._rotation == nrs_default_v3pa
 
 
 def test_IFU_wavelengths():
@@ -91,3 +94,23 @@ def test_IFU_wavelengths():
     # and test we can specify a reduced wavelength sampling:
     for n in (10, 100):
         assert len(nrs.get_IFU_wavelengths(n)) == n
+
+
+def test_aperture_rotation_updates():
+    """ Test that switching detector or aperture updates the aperture PA
+    (this is a tiny detail)"""
+    nrs = webbpsf_core.NIRSpec()
+    pa_nrs1_full = nrs._rotation
+
+    # changing aperture updates PA
+    nrs.set_position_from_aperture_name('NRS_S200A1_SLIT')
+    assert nrs._rotation != pa_nrs1_full
+
+    # change back to original aperture
+    nrs.set_position_from_aperture_name('NRS1_FULL')
+    assert nrs._rotation == pa_nrs1_full
+
+    # changing detector should update aperturename and also update PA
+    nrs.detector = 'NRS2'
+    assert nrs.aperturename == 'NRS2_FULL'
+    assert nrs._rotation != pa_nrs1_full

webbpsf/webbpsf_core.py

@@ -3327,6 +3327,9 @@ def aperturename(self, value):
                         self.image_mask = None
                 else:
                     self._mode = 'imaging'  # More to implement here later!
+        # Update the rotation angle
+        # This works the same for both regular and IFU modes
+        self._rotation = self._get_aperture_rotation(self.aperturename)
 
     def _tel_coords(self):
         """Convert from science frame coordinates to telescope frame coordinates using
@@ -3356,6 +3359,19 @@ def _get_pixelscale_from_apername(self, apername):
         else:
             return super()._get_pixelscale_from_apername(apername)
 
+    def _get_aperture_rotation(self, apername):
+        """Get the rotation angle of a given aperture, using values from SIAF.
+
+        Returns ~ position angle counterclockwise from the V3 axis, in degrees
+        (i.e. SIAF V3IdlYangle)
+
+        For NIRSpec this is simple, since even the SLIT type apertures have
+        V3IdlYAngle values defined.  And we don't have the complexity of
+        COMPOUND type apertures that MIRI has to deal with.
+
+        """
+        return self.siaf[apername].V3IdlYAngle
+
     @property
     def disperser(self):
         """NIRSpec spectral dispersing element (grating or prism).