Look up Roman sky backgrounds by column names

The index based lookup for sky backgrounds is finicky when requesting
only a subset of bandpasses. This could be done by looking up the index
of the bandname, but looking up by column name is more robust and has
the advantage of documenting the shared data file better.

Author: arunkannawadi

galsim/roman/roman_bandpass.py

@@ -123,9 +123,9 @@ def getBandpasses(AB_zeropoint=True, default_thin_trunc=True, include_all_bands=
 
     # Read in and manipulate the sky background info.
     sky_file = os.path.join(meta_data.share_dir, "roman", "roman_sky_backgrounds.txt")
-    sky_data = np.loadtxt(sky_file).transpose()
-    ecliptic_lat = sky_data[0, :]
-    ecliptic_lon = sky_data[1, :]
+    sky_data = np.genfromtxt(sky_file, names=True)
+    ecliptic_lat = sky_data['Latitude']
+    ecliptic_lon = sky_data['Longitude']
 
     # Parse kwargs for truncation, thinning, etc., and check for nonsense.
     truncate_kwargs = ['blue_limit', 'red_limit', 'relative_throughput']
@@ -172,7 +172,7 @@ def getBandpasses(AB_zeropoint=True, default_thin_trunc=True, include_all_bands=
         # Store the sky level information as an attribute.
         bp._ecliptic_lat = ecliptic_lat
         bp._ecliptic_lon = ecliptic_lon
-        bp._sky_level = sky_data[2+index, :]
+        bp._sky_level = sky_data[bp_name]
 
         # Add it to the dictionary.
         bp.name = bp_name if bp_name != 'W149' else 'W146'

share/roman/roman_sky_backgrounds.txt

@@ -1,3 +1,4 @@
+# Latitude Longitude R062 Z087 Y106 J129 H158 F184 W146 K213 SNPrism Grism_1stOrder Grism_0thOrder
 0.0000 0.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000
 1.3976 0.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000
 2.7960 0.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000 -10.0000