diff --git a/Installation-(ROS-Melodic).md b/Installation-(ROS-Melodic).md
index 2578e22..7d8c79d 100644
--- a/Installation-(ROS-Melodic).md
+++ b/Installation-(ROS-Melodic).md
@@ -6,7 +6,10 @@ This page collects information on how to install the simulator on a newer ROS ve
 ```
 catkin config --extend /opt/ros/melodic --cmake-args -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS=-Wno-int-in-bool-context
 ```
-## Hector Trajectory Server
+## (Optional) Hector Trajectory Server
+
+**Note**: this step is optional. ESIM does not need the hector trajectory server. It is only used to display the camera trajectory in RVIZ for visualization.
+
 The hector trajectory server package is not available for ros melodic. But we can manually compile it together with the other dependencies. Download the packages from [their Github Repository](https://github.com/tu-darmstadt-ros-pkg/hector_slam) and put them in the source directory, next to rpg_esim (`sim_ws/src`). The packages are detected `catkin` during a regular compilation process.
 
 Required Packages: