Space shuttle Discovery (Mission 51-D, 12-19 April 1985) showing Astronauts David Griggs (right) & Jeffrey A. Hoffman performing an extravehicular activity to attach a snag-type device (fashioned on board Discovery) to the end of the remote manipulator system (robot arm). Extensions to the arm were required to attempt to redeploy the disabled Syncom 4 communications satellite (also known as LEASAT). Although the attachment was successful, later efforts to redeploy the satellite failed.