Workers check the installation of an engine controller in one of the three main engines of the orbiter Discovery.

In the Space Shuttle Maine Engine Shop, workers check the installation of an engine controller in one of the three main engines of the orbiter Discovery. The controller is an electronics package mounted on each space shuttle main engine. It contains two digital computers and the associated electronics to control all main engine components and operations. The controller is attached to the main combustion chamber by shock-mounted fittings. Discovery is the designated orbiter for mission STS-120 to the International Space Station. It will carry a payload that includes the Node 2 module, named Harmony. Launch is targeted for no earlier than Oct. 20. Photo credit: NASA/Cory Huston