Space Station Extravehicular Activity

A New Generation of Space Robotics

This photo of Expedition Two Astronauts Susan Helms and Jim Voss looking through the window of the Destiny Laboratory Module shows the Space Vision System targets -- the black and white circles -- on the module's surface.

To build and maintain the International Space Station, space walking astronauts will work in partnership with a new generation of space robotics. The space shuttle's mechanical arm and a new space station arm operate both as "space cranes" to precisely maneuver large modules and components and also as space "cherry pickers" to maneuver astronauts to work areas.

The shuttle's Canadian-built mechanical arm has been enhanced with a new "Space Vision System" (SVS) that helps the operator literally see around corners. Tested on past space shuttle missions STS-74, STS-80 and STS-85, the SVS uses video image processing and a series of markings on the objects being maneuvered to develop a graphical laptop computer display to assist the arm operator. It allows the shuttle arm to be operated with great precision even when visibility is obstructed, and the system was used operationally during the first assembly mission as Astronaut Nancy Currie, with her view partially obstructed, attached the first station component, the Zarya Control Module, to the second component, the Unity Connecting Module.

The Canadian Mobile Servicing System will contain the Space Station Remote Manipulator System, the Mobile Base System and the Special Purpose Dexterous Manipulator.

Canada also has provided the new station mechanical arm. Called the Space Station Remote Manipulator System (SSRMS), or Canadarm2, the 55-foot-long arm was launched on April 19, 2001 aboard Space Shuttle Endeavour during STS-100. The station arm has the capability to move around the station's exterior like an inchworm, locking its free end on one of many special fixtures -- called Power and Data Grapple Fixtures, or PDGFs -- placed strategically around the station, and then detaching its other end and pivoting it forward. Eventually, the station arm will be able to ride on a Mobile Servicing System, or MSS, platform that will move on tracks along the length of the station's 360-foot truss, putting much of the station within grasp of the arm.

As the ISS grows, more PDGFs will be added, some fixed, and some on a mobile trolley, allowing the arm to move about and reach the new sections of the ISS. Canada also is providing a new robotic "Canada Hand" for the station, called the Special Purpose Dexterous Manipulator, scheduled to be launched in 2003. The "hand" consists of two small robotic arms that can be attached to the end of the main station arm to conduct more intricate maintenance tasks.

Two other robotic arms will be on the International Space Station. A European Robotic Arm (ERA) built by the European Space Agency will be used for maintenance on the Russian segment of the station and the Japanese laboratory module will include a Japanese robotic arm that will tend exterior experiments mounted on a "back porch" of the lab. In addition to mechanical arms, other robotics that may be used aboard the station include a free-flying robotic camera, a prototype of which was tested during a 1997 space shuttle mission, that may be used to inspect the exterior of the station, including the acre of solar panels. Called the AERCam, more flight tests may be planned on future shuttle missions.