The Canadarm is perhaps one of the most well-known Canadian accomplishments in space. Designed and built by the Canadian firm Spar Aerospace Ltd., the Canadarm was a gift from Canada to NASA's space shuttle program. The first Canadarm, technically called the SRMS (Space shuttle Remote Manipulator System), flew on the shuttle Columbia in 1981. NASA then bought Canadarms to equip the rest of the shuttle fleet.
Although the Canadarm flies on board the shuttle, its primary function involves satellites. The Canadarm has consistently and successfully been used to release satellites into orbit, retrieve them if they malfunction, and aid in their repair.
When the shuttle carries satellites into space, the Canadarm reaches into the Payload Bay of the shuttle and lifts the satellite out. After the satellite has been checked and confirmed ready for release, the Canadarm releases the satellite and the shuttle maneuvers away.
So that the Canadarm can grip the satellites, a special foot-long metal prong is attached to the satellite's bus (commonly known as the body of the satellite). This prong is called a grapple fixture. Inside the end of the Canadarm are three snare wires. Small motors constrict the wires, wrapping them tightly around the grapple fixture. The wires are then retracted, and the satellite is pulled snugly against the end of the arm. The Canadarm is unable to grasp older satellites because they were not fitted with grapple fixtures when they were originally launched.
Besides routine satellite launching jobs, the Canadarm is also used to repair satellites in trouble. The Canadarm has saved several very costly satellite projects from disaster.
The first on-orbit repair job was of NASA's $235 million Solar Max satellite. Solar Max was launched to study solar flares. After 10 months, three fuses blew in the satellite causing several of the satellite's instruments to fail.
On the space shuttle Challenger flight in 1984, astronaut George Nelson was supposed to recapture the satellite from a Manned Maneuvering Unit (MMU). When he reached Solar Max, however, he found that the special tool he had been given to grapple the satellite did not fit! Fortunately, Mission Commander Robert Crippen, with the last of the orbiter's maneuvering fuel, was able to bring the orbiter close enough to the satellite so that the Canadarm could grab it.
Once Solar Max was safely in the Payload Bay, the Canadarm once again came to the aid of the astronauts. By standing with their feet clamped to a work platform fixed to the Canadarm, astronauts could be moved easily and accurately to the parts of the satellite needing repair. This also left their arms free for doing repair jobs.
Thanks to the Canadarm, Solar Max could then be redeployed into orbit for several more years of profitable scientific research.
Since the Solar Max rescue mission, the Canadarm has been essential to many satellite repair jobs. For example, the Canadarm was twice used to recapture and then redeploy the Hubble Space Telescope. After extensive repairs in 1993 and 1997, the Hubble telescope was able to take clear and precise pictures of stellar phenomena vast distances away from the Earth.
The Canadarm is now routinely employed to make satellite launch, retrieval, and repair easier and more efficient tasks.