The Mobile Servicing System (MSS) is a robotic arm and associated equipment on the International Space Station that 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 robotics training to enable them to perform these functions with the arm.

The station is scheduled to receive a second robotic arm, the European Robotic Arm.

The MSS has three parts:

Canadarm2

Launched on STS-100 in April 2001, this next generation Canadarm is a bigger, better, smarter version of the space shuttle's original robotic arm. Canadarm2 is 17.6 meters (57.7 ft) long when fully extended and has seven motorized joints. It has a mass of 1,800 kilograms (4,000 lb) and a diameter of 35 cm (13.8 in). The arm is capable of handling large payloads of up to 116,000 kg (256,000 lb) and assisting with docking the space shuttle. The Space Station Remote Manipulator System, or SSRMS, is self-relocatable with a Latching End Effector, so it can be attached to complementary ports spread throughout the station's exterior surfaces.

Canadarm2 can move end-over-end to reach many parts of the Space Station in an inchworm-like movement, limited only by the number of Power Data Grapple Fixtures (PDGFs) on the station. PDGFs located around the station provide power, data and video to the arm through its Latching End Effectors (LEEs). The arm can also travel the entire length of the space station using the Mobile Base System.

Most of the time the arm operators see what they are doing by looking at the Advanced Space Vision System screen next to the arm control panel.

Mobile Base System

A work platform that moves along rails covering the length of the space station, the Mobile Base System, or MBS, provides lateral mobility for the Canadarm2 as it traverses the main trusses. It was added to the station during STS-111 in June 2002.

Special Purpose Dexterous Manipulator

The Special Purpose Dexterous Manipulator, or Canada Hand, is a smaller two-armed robot capable of handling the delicate assembly tasks currently handled by astronauts during space walks. Testing was done in the space simulation chambers of the Canadian Space Agency's David Florida Laboratory in Ottawa. The manipulator is scheduled to be transported to the station no earlier than 2005.