change FoVAlignment based on meta infos

Signed-off-by: Quentin Remy <[email protected]>
SimoneMender · Jul 30, 2024 · 9662926 · 9662926
1 parent fa0cef3
commit 9662926
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Showing 5 changed files with 35 additions and 6 deletions.
diff --git a/gammapy/data/metadata.py b/gammapy/data/metadata.py
@@ -107,6 +107,8 @@ def from_header(cls, header, format="gadf"):
             "PRESSURE",
             "RELHUM",
             "NSBLEVEL",
+            "CREATOR",
+            "HDUVERS",
         ]
         optional = dict()
         for key in optional_keywords:

diff --git a/gammapy/data/observations.py b/gammapy/data/observations.py
@@ -15,6 +15,7 @@
 from astropy.units import Quantity
 from astropy.utils import lazyproperty
 import matplotlib.pyplot as plt
+from gammapy.irf import FoVAlignment
 from gammapy.utils.deprecation import GammapyDeprecationWarning, deprecated
 from gammapy.utils.fits import LazyFitsData, earth_location_to_dict
 from gammapy.utils.metadata import CreatorMetaData, TargetMetaData, TimeInfoMetaData
@@ -67,7 +68,7 @@ class Observation:
     aeff = LazyFitsData(cache=False)
     edisp = LazyFitsData(cache=False)
     psf = LazyFitsData(cache=False)
-    bkg = LazyFitsData(cache=False)
+    _bkg = LazyFitsData(cache=False)
     _rad_max = LazyFitsData(cache=True)
     _events = LazyFitsData(cache=False)
     _gti = LazyFitsData(cache=True)
@@ -101,7 +102,7 @@ def __init__(
         self.aeff = aeff
         self.edisp = edisp
         self.psf = psf
-        self.bkg = bkg
+        self._bkg = bkg
         self._rad_max = rad_max
         self._gti = gti
         self._events = events
@@ -116,6 +117,25 @@ def _repr_html_(self):
         except AttributeError:
             return f"<pre>{html.escape(str(self))}</pre>"
 
+    @property
+    def bkg(self):
+        """Background of the observation."""
+        bkg = self._bkg
+        # used for backward compatibility of old HESS data
+        if (
+            bkg
+            and self._meta
+            and self._meta.optional
+            and self._meta.optional["CREATOR"] == "SASH FITS::EventListWriter"
+            and self.meta.optional["HDUVERS"] == "0.2"
+        ):
+            bkg._fov_alignment = FoVAlignment.REVERSE_LON_RADEC
+        return bkg
+
+    @bkg.setter
+    def bkg(self, value):
+        self._bkg = value
+
     @property
     def meta(self):
         """Return metadata container."""

diff --git a/gammapy/irf/core.py b/gammapy/irf/core.py
@@ -33,6 +33,9 @@ class FoVAlignment(str, Enum):
 
     ALTAZ = "ALTAZ"
     RADEC = "RADEC"
+    REVERSE_LON_RADEC = (
+        "REVERSE_LON_RADEC"  # used for backward compatibility of old HESS data
+    )
 
 
 class IRF(metaclass=abc.ABCMeta):

diff --git a/gammapy/makers/tests/test_spectrum.py b/gammapy/makers/tests/test_spectrum.py
@@ -7,6 +7,7 @@
 from regions import CircleSkyRegion
 from gammapy.data import DataStore
 from gammapy.datasets import SpectrumDataset
+from gammapy.irf import FoVAlignment
 from gammapy.makers import (
     ReflectedRegionsBackgroundMaker,
     SafeMaskMaker,
@@ -125,6 +126,11 @@ def test_spectrum_dataset_maker_hess_dl3(spectrum_dataset_crab, observations_hes
 
     datasets = []
     for obs in observations_hess_dl3:
+
+        assert obs.meta.optional["CREATOR"] == "SASH FITS::EventListWriter"
+        assert obs.meta.optional["HDUVERS"] == "0.2"
+        assert obs.bkg.fov_alignment == FoVAlignment.REVERSE_LON_RADEC
+
         dataset = maker.run(spectrum_dataset_crab, obs)
         datasets.append(dataset)
 

diff --git a/gammapy/makers/utils.py b/gammapy/makers/utils.py
@@ -13,8 +13,6 @@
 from gammapy.utils.coordinates import sky_to_fov
 from gammapy.utils.regions import compound_region_to_regions
 
-REVERSE_FOV_LON = False
-
 __all__ = [
     "make_counts_rad_max",
     "make_edisp_kernel_map",
@@ -83,14 +81,14 @@ def _get_fov_coords(pointing, irf, geom, use_region_center=True, obstime=None):
             fov_lon, fov_lat = sky_to_fov(
                 altaz_coord.az, altaz_coord.alt, pointing_altaz.az, pointing_altaz.alt
             )
-        elif irf.fov_alignment == FoVAlignment.RADEC:
+        elif irf.fov_alignment in [FoVAlignment.RADEC, FoVAlignment.REVERSE_LON_RADEC]:
             fov_lon, fov_lat = sky_to_fov(
                 sky_coord.icrs.ra,
                 sky_coord.icrs.dec,
                 pointing_icrs.icrs.ra,
                 pointing_icrs.icrs.dec,
             )
-            if REVERSE_FOV_LON:
+            if irf.fov_alignment == FoVAlignment.REVERSE_LON_RADEC:
                 fov_lon = -fov_lon
         else:
             raise ValueError(