diff --git a/tm/obsw_tm_service_3.py b/tm/obsw_tm_service_3.py
index d5b0d0e8f18c9d319c559d08024e743a52d3a95a..b6f8419c6a46bcded7a253759e85ac419860cc5c 100644
--- a/tm/obsw_tm_service_3.py
+++ b/tm/obsw_tm_service_3.py
@@ -67,6 +67,7 @@ class Service3TM(PusTelemetry):
             self.handle_test_hk_data()
 
     def handle_gps_hk_data(self):
+        # TODO: size check. sth not right with gps 0 test
         self.numberOfParameters = 9
         self.hkHeader = ["Fix Mode", "SV in Fix", "GNSS Week", "Time of Week", "Latitude",
                          "Longitude", "Mean Sea Altitude", "Position X", "Position Y", "Position Z",