Add observaton reason to exposure and visit registry

python/lsst/obs/base/_instrument.py

@@ -581,6 +581,7 @@ def makeExposureRecordFromObsInfo(obsInfo, universe):
         exposure_time=obsInfo.exposure_time.to_value("s"),
         dark_time=obsInfo.dark_time.to_value("s"),
         observation_type=obsInfo.observation_type,
+        observation_reason=obsInfo.observation_reason,
         physical_filter=obsInfo.physical_filter,
         science_program=obsInfo.science_program,
         target_name=obsInfo.object,

python/lsst/obs/base/defineVisits.py

@@ -361,6 +361,11 @@ def _buildVisitRecords(self, definition: VisitDefinitionData, *,
                                     (e.target_name for e in definition.exposures))
         science_program = _reduceOrNone(lambda a, b: a if a == b else None,
                                         (e.science_program for e in definition.exposures))
+        observation_reason = _reduceOrNone(lambda a, b: a if a == b else None,
+                                           (e.observation_reason for e in definition.exposures))
+        if observation_reason is None:
+            # Be explicit about there being multiple reasons
+            observation_reason = "various"
 
         # Use the mean zenith angle as an approximation
         zenith_angle = _reduceOrNone(sum, (e.zenith_angle for e in definition.exposures))
@@ -376,6 +381,7 @@ def _buildVisitRecords(self, definition: VisitDefinitionData, *,
                 physical_filter=physical_filter,
                 target_name=target_name,
                 science_program=science_program,
+                observation_reason=observation_reason,
                 zenith_angle=zenith_angle,
                 visit_system=self.groupExposures.getVisitSystem()[0],
                 exposure_time=exposure_time,