diff --git a/Catalog/Catalog_example.py b/Catalog/Catalog_example.py
index d884f35991f03230e6dab974a02cc69b67a55e31..db6fb5a7ac7257199ed3b8858d8292b3d68b68e2 100644
--- a/Catalog/Catalog_example.py
+++ b/Catalog/Catalog_example.py
@@ -40,6 +40,8 @@ class Catalog_example(CatalogBase):
         ----------
         config : dict
             configuration dictionary which is parsed from the input YAML file
+        chip: ObservationSim.Instrument.Chip
+            a ObservationSim.Instrument.Chip object, can be used to identify the band etc.
         **kwargs : dict
             other needed input parameters (in key-value pairs), please modify corresponding
             initialization call in "ObservationSim.py" as you need.