Fix typo in coordinate lookup for grid shadowing (#156)

* Fix typo in coordiante lookup for grid shadowing

* Switch grid shadowing to use SkyCoords

Author: samaloney

changelog/156.bugfix.rst

@@ -0,0 +1 @@
+Fix typo in `~stixpy.calibration.visibility.create_meta_pixels` which cased error if grid shadow correction was enabled. Also update grid calculations to use `Skycoord` objects.

stixpy/calibration/grid.py

@@ -10,8 +10,10 @@
 
 __all__ = ["get_grid_transmission", "_calculate_grid_transmission"]
 
+from stixpy.coordinates.frames import STIXImaging
 
-def get_grid_transmission(xy_flare):
+
+def get_grid_transmission(flare_location: STIXImaging):
     r"""
     Return the grid transmission for the 32 sub-collimators corrected for internal shadowing.
 
@@ -20,11 +22,8 @@ def get_grid_transmission(xy_flare):
 
     Parameters
     ----------
-    xy_flare
-
-    Returns
-    -------
-
+    flare_location :
+        Location of the flare
     """
     column_names = ["sc", "p", "o", "phase", "slit", "grad", "rms", "thick", "bwidth", "bpitch"]
 
@@ -33,10 +32,8 @@ def get_grid_transmission(xy_flare):
     front = Table.read(grid_info / "grid_param_front.txt", format="ascii", names=column_names)
     rear = Table.read(grid_info / "grid_param_rear.txt", format="ascii", names=column_names)
 
-    xy_flare_stix = np.array([xy_flare[0].value, xy_flare[1].value]) * u.arcsec
-
-    transmission_front = _calculate_grid_transmission(front, xy_flare_stix)
-    transmission_rear = _calculate_grid_transmission(rear, xy_flare_stix)
+    transmission_front = _calculate_grid_transmission(front, flare_location)
+    transmission_rear = _calculate_grid_transmission(rear, flare_location)
     total_transmission = transmission_front * transmission_rear
 
     # The finest grids are made from multiple layers for the moment remove these and set 1
@@ -49,15 +46,15 @@ def get_grid_transmission(xy_flare):
     return final_transmission
 
 
-def _calculate_grid_transmission(grid_params, xy_flare_stix):
+def _calculate_grid_transmission(grid_params, flare_location):
     r"""
     Calculate grid transmission accounting for internal shadowing.
 
     Parameters
     ----------
     grid_params
         Grid parameter tables
-    xy_flare_stix
+    flare_location
         Position of flare in stix imaging frame
 
     Returns
@@ -68,7 +65,7 @@ def _calculate_grid_transmission(grid_params, xy_flare_stix):
     pitch = grid_params["p"]
     slit = grid_params["slit"]
     thick = grid_params["thick"]
-    flare_dist = np.abs(xy_flare_stix[0] * np.cos(orient)) + xy_flare_stix[1] * np.sin(orient)
+    flare_dist = np.abs(flare_location.Tx * np.cos(orient)) + flare_location.Ty * np.sin(orient)
     shadow_width = thick * np.tan(flare_dist)
     transmission = (slit - shadow_width) / pitch
     return transmission

stixpy/calibration/tests/test_grid.py

@@ -1,16 +1,18 @@
 import astropy.units as u
 import numpy as np
 import pytest
+from astropy.coordinates import SkyCoord
 
 from stixpy.calibration.grid import get_grid_transmission
+from stixpy.coordinates.frames import STIXImaging
 
 
 # Output values taken from IDL routine
 @pytest.mark.parametrize(
     "input,out",
     [
         (
-            [0, 0] * u.arcsec,
+            SkyCoord(*[0, 0] * u.arcsec, frame=STIXImaging),
             [
                 [
                     0.38359416,
@@ -49,7 +51,7 @@
             ],
         ),
         (
-            [0, 500.0] * u.arcsec,
+            SkyCoord(*[0, 500.0] * u.arcsec, frame=STIXImaging),
             [
                 0.38119361,
                 0.23916472,

stixpy/calibration/tests/test_visibility.py

@@ -137,6 +137,18 @@ def test_create_meta_pixels_timebins(flare_cpd):
     assert_quantity_allclose(np.sum(flare_cpd.duration[0:3]), meta_pixels["time_range"].dt.to(u.s))
 
 
+def test_create_meta_pixels_shadow(flare_cpd):
+    energy_range = [6, 12] * u.keV
+    time_range = [flare_cpd.times[0], flare_cpd.times[2]]
+    create_meta_pixels(
+        flare_cpd,
+        time_range=time_range,
+        energy_range=energy_range,
+        flare_location=STIXImaging(0 * u.arcsec, 0 * u.arcsec),
+        no_shadowing=False,
+    )
+
+
 @pytest.mark.parametrize(
     "pix_set, real_comp",
     [

stixpy/calibration/visibility.py

@@ -196,9 +196,9 @@ def create_meta_pixels(
 
     if not no_shadowing:
         if not isinstance(flare_location, STIXImaging) and flare_location.obstime != time_range.center:
-            roll, solo_heeq, stix_pointing = get_hpc_info(time_range.start, time_range.stop)
+            roll, solo_heeq, stix_pointing = get_hpc_info(time_range.start, time_range.end)
             flare_location = flare_location.transform_to(STIXImaging(obstime=time_range.center, observer=solo_heeq))
-        grid_shadowing = get_grid_transmission(flare_location.xyz[::-1])
+        grid_shadowing = get_grid_transmission(flare_location)
         ct_summed = ct_summed / grid_shadowing.reshape(-1, 1) / 4  # transmission grid ~ 0.5*0.5 = .25
         ct_error_summed = ct_error_summed / grid_shadowing.reshape(-1, 1) / 4