Astronaut Dale Gardner approaches the Westar 6 satellite, using the Manned Manoeuvring Unit (MMU), prior to capturing it and bringing it back to Discovery's cargo bay. Discovery brought two communication satellites, Westar 6 and Palapa B2, back to Earth during this mision, 51-A, in November 1984. The MMU has small gas thrusters which enable an astronaut to move around outside the Space Shuttle without a tether. It was first flown by astronaut Bruce McCandles on the Space Shuttle Challenger 41-B (STS-10) mision in February 1984.
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