Automatically download IERS A table if needed

Closes #197
mwcraig · May 22, 2015 · 2b11f9d · 2b11f9d
1 parent 3863ef2
commit 2b11f9d
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Showing 2 changed files with 27 additions and 2 deletions.
diff --git a/msumastro/header_processing/patchers.py b/msumastro/header_processing/patchers.py
@@ -54,6 +54,22 @@ def IRAF_image_type(image_type):
     return image_type.split()[0].upper()
 
 
+def _lst_from_obstime(obstime):
+    try:
+        LST = obstime.sidereal_time('apparent',
+                                    longitude=feder.site.longitude)
+    except IndexError:
+        # We are outside the range of the IERS table installed with astropy,
+        # so get a newer one.
+        from astropy.utils import iers
+        from astropy.utils.data import download_file
+        iers.IERS.iers_table = iers.IERS_A.open(download_file(iers.IERS_A_URL,
+                                                cache=True))
+        LST = obstime.sidereal_time('apparent',
+                                    longitude=feder.site.longitude)
+    return LST
+
+
 def add_time_info(header, history=False):
     """
     Add JD, MJD, LST to FITS header
@@ -69,7 +85,8 @@ def add_time_info(header, history=False):
     feder.JD_OBS.value = dateobs.jd
     feder.MJD_OBS.value = dateobs.mjd
 
-    LST_tmp = dateobs.sidereal_time('apparent', longitude=feder.site.longitude)
+    LST_tmp = _lst_from_obstime(dateobs)
+
     feder.LST.value = LST_tmp.to_string(unit=u.hour, sep=':', precision=4,
                                         pad=True)
 
@@ -122,7 +139,7 @@ def add_object_pos_airmass(header, history=False):
     feder.AIRMASS.value = round(1 / np.cos(np.pi / 2 - alt_az.alt.radian), 3)
 
     # TODO: replace the LST calculation
-    LST = obstime.sidereal_time('apparent', longitude=feder.site.longitude)
+    LST = _lst_from_obstime(obstime)
     HA = LST.hour - obj_coord2.ra.hour
     HA = Angle(HA, unit=u.hour)
 

diff --git a/msumastro/header_processing/tests/test_patchers.py b/msumastro/header_processing/tests/test_patchers.py
@@ -17,6 +17,7 @@
 from astropy import units as u
 from astropy.table import Table
 from astropy.extern import six
+from astropy.time import Time
 
 from .. import patchers as ph
 from ..feder import Feder, ApogeeAltaU9, FederSite
@@ -627,6 +628,13 @@ def test_unit_is_added():
             assert h['BUNIT'] == str(instrument.image_unit)
 
 
+def test_lst_in_future():
+    header = fits.Header()
+    future = Time.now() + 1 * u.year
+    header['date-obs'] = future.isot
+    ph.add_time_info(header)
+
+
 @pytest.fixture(params=['object', 'OBJECT', 'Object'])
 def object_file_ra_change_col_case(request):
     object_file_with_ra_dec(_test_dir, object_col_name=request.param)