Use field given by Swift team

gracedb/events/translator.py

@@ -653,8 +653,8 @@ def populateGrbEventFromVOEventFile(filename, event):
     event.trigger_id = trigger_id
 
     # Swift subthreshold GRBs have an extra FAR field
-    if 'FAR' in VOEvent_params:
-        event.far = float(VOEvent_params.get('FAR').get('value'))
+    if 'BAT_FAR' in VOEvent_params:
+        event.far = float(VOEvent_params.get('BAT_FAR').get('value'))
 
     # Save event
     event.save()