Satellite repair in space. Astronaut James van Hoften makes his way back to the airlock of Shuttle Challenger having helped repair the Solar Maximum Mission (SMM) satellite. The SMM can be seen protruding from the far end of the cargo bay. This mission, 41-C, was the first in which a satellite was successfully retrieved from orbit, repaired and then redeployed. This was needed to free a jammed communications antenna without which the satellite was useless. During the same mission of 6-12 April 1984, the Long Duration Exposure Facility (LDEF) satellite was deployed. Van Hoften is wearing a Manned Manoeuvering Unit (MMU) back- pack, used here for the first time in orbit.