The Mobile Servicing System (MSS), better known by its primary component Canadarm2, is a robotic system and associated equipment on the International Space Station. It plays a key role in station assembly and maintenance: moving equipment and supplies around the station, supporting astronauts working in space, and servicing instruments and other payloads attached to the space station. Astronauts receive specialized training to enable them to perform these functions with the various systems.
The MSS is composed of the actual arm called Space Station Remote Manipulator (SSRMS), the Mobile Remote Servicer Base System (MBS) and the Special Purpose Dexterous Manipulator (SPDM also known as Dextre or Canada hand). The system can move along rails on the Integrated Truss Structure on top of the US provided Mobile Transporter cart which hosts the MRS Base System.
Author/Origin: NASA Johnson Space Center http://www.nasa.gov/centers/johnson/home/