• The Canadarm can be used for launching or retrieving satellites (satellites can also be launched using rockets)
• So that the Canadarm can grip these satellites, they are built with a part called a grapple fixture, which is attached to the bus of the satellite
• The original grapple fixture consisted of a foot-long metal pin, a baseplate, and a target
• The end of the Canadarm (called its End Effector) has three snare wires which wrap around the grapple fixture using small motors
• The wires are then retracted, and the satellite is pulled snugly against the end of the Canadarm
• Today, grapple fixtures have removable grapple pins so that if the Canadarm fails, an astronaut can manually remove the pin to release the satellite
• Grapple fixtures now have an electrical connector on the end of the pin
• This can join with an electrical adaptor (called a Special Purpose End Effector or SPEE) at the end of the Canadarm
• This allows electrical power and data communications to move from the shuttle to the satellite when it is grappled
• This is used to preserve a satellite's batteries during deploy and retrieval activities
• The Canadarm is unable to grasp older satellites, or satellites not expected to be repaired in orbit, because they were not fitted with grapple fixtures when they were originally launched
• The Canadarm can also only capture satellites which are in the same orbital path as the shuttle (for example, the shuttle never flies in a polar orbit)