Another package missing(Example 8.11)

Hello,

I am not able to launch the first code in the example 8.11(roslaunch ardrone_as action_server.launch). I am getting an error like below.

I try to find the ardrone_as package using roscd ardrone_as, but it says there is no package name called ardrone_as. The error is shown below.
---------- error ----------
user:~/catkin_ws$ roscd ardrone_as
roscd: No such package/stack ‘ardrone_as’

How can I fix this error?

Maybe the sourcing has ben unset. Try to launch the command in a new terminal.

Please refer to this post:
Package is missing - Course Support / ROS Basics In 5 Days (C++) - The Construct ROS Community (robotigniteacademy.com)