Mobile Servicing System


The Mobile Servicing System (MSS) is a sophisticated robotics suite that assembled the Station in space, module by module. Developed for the Canadian Space Agency (CSA) by MacDonald, Dettwiler and Associates Ltd. (MDA) of Brampton, Ontario, the MSS is comprised of three robots that work together or independently:

  • Canadarm2, a 17-metre long robotic arm essential to the construction of the Space Station. Since it was installed in 2001, Canadarm2 has been used to assemble the Station, and move supplies, equipment and even astronauts. It is also used to capture free-flying spacecraft to dock them to the International Space Station (ISS).
  • Dextre, the Station's two-armed robotic "handyman," is used for routine maintenance, such as changing batteries, which reduces the need for astronauts to perform risky spacewalks and frees up their time for science.
  • The Mobile Base is a moveable work platform and storage facility that slides on rails across the Space Station's main truss (or backbone) to transport Canadarm2, Dextre or equipment from one location to another.

All astronauts and flight controllers assigned to operate the MSS undergo intensive training at the CSA's headquarters in Saint-Hubert, Quebec. Robotics flight controllers at the Agency regularly assist the crew on board the Station with robotics operations, and can also operate the MSS from the ground. Mission planners also spend months plotting the MSS's every movement and testing operations in simulators prior to each task.


With the collaboration of MD Robotics, prime contractor of the MSS.

Mobile Base System Canadarm2 Dextre
  MSS Canadarm2 DEXTRE
Length (metres) 5.7 x 4.5
x 2.9
17.6 3.5
Mass (approx.) 1500 kg 1641 kg 1662 kg
Mass Handling Capacity 20,900 kg 116,000 kg 600 kg
Degrees of Freedom Fixed 7 15
Peak Power (operational) 825 W 2000 W 2000 W
Average Power (keep alive) 365 W 1200 W 600 W
Stopping Distance (Under Maximum Load) N/A 0.6 m 0.05 m