The Solar Maximum Mission satellite, otherwise known as Solar Max, was launched in February 1980 to study the Sun during the years of peak sunspot activity. After just eight months one of its instruments and its attitude control system failed. In April 1984 NASA embarked on an unprecedented in-orbit recovery and repair mission to restore Solar Max to full health. This called for shuttle astronauts riding in MMUs (manned manoeuvring units) to undertake daring EVAs to capture the ailing satellite and then replace the faulty equipment. The mission scheduled for the operation, using orbiter Challenger, was STS-41C, which began on April 6, 1984. On the third day of the mission astronaut George Nelson 'flew' the MMU over to the slowly rotating Solar Max and attempted to dock with it using a specially designed attachment. The idea was to latch on to it and fire the MMU's thrusters to stop it spinning. Then it could be captured by Challenger's remote manipulator system (RMS) arm and dropped into the payload bay. Nelson was unable to dock, however, and actually made the satellite's gyrations worse. Mission controllers at the Goddard Space Center luckily managed to steady the craft enough for the RMS arm to grab it and place it in the payload bay. Next day Nelson and fellow spacewalker James van Hoften set to work to replace the faulty equipment. Despite being hampered by bulky gloves and weightlessness, they carried out the repairs remarkably quickly. Afterwards Solar Max was lifted out of the payload bay and redeployed into orbit. Tests showed that it now worked perfectly again, and it soon began to send back valuable data. Ironically, the very events Solar Max was sent aloft to observe - activity on the Sun such as solar flares and storms - led to its premature death. Especially fierce solar activity in the late 1980s so expanded the Earth's atmosphere that Solar Max suffered increased drag. It fell from orbit and burned up in the atmosphere on December 22, 1989.
