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Twenty-seven years ago this week, the Solar Max satellite was retrieved from, repaired in and redeployed to orbit by the crew of STS 41-C.  The historic event marked the first time in the annals of spaceflight that a satellite was repaired on-orbit.

Space Transportation System (STS) 41-C was one of the most eventful and historic missions of the Space Shuttle Program.  The first Shuttle direct ascent was flown, a crippled satellite was repaired in orbit for the first time, a major space research facility was deployed and the famed IMAX camera was first used in space.

STS 41-C was the 11th Space Shuttle mission and the 5th flown by the Challenger orbiter.  Mission Commander for STS 41-C was Robert L. Crippen, who was making his 3rd Shuttle flight.  The other crew members were space rookies.  They included Francis R. “Dick” Scobee, Pilot and Mission Specialists George D. “Pinkie” Nelson, James D. A. “Ox” van Hoften and Terry J. Hart.

STS 41-C was launched from LC-39A at Cape Canaveral, Florida on Friday, 06 April 1984.  Lift-off time was 13:58 UTC.  The direct ascent profile initially placed the Challenger in a 288-nm circular orbit.  The Orbiter’s lift-off mass of 254,254 lbs included 57,279 lbs of payload.

After raising Challenger’s orbit to 313-nm, the STS 41-C crew performed a rendezvous with the malfunctioning Solar Maximum satellite on the third day of the mission.  Using the newly-developed Manned Maneuvering Unit (MMU), Mission Specialist Nelson flew out to meet Solar Max which was stationed about 200 feet from the Orbiter.  His intent was to grapple it and bring it back into the Challenger payload bay for repairs.

Nelson was equipped with a tool called the Trunnion Pin Acquisition Device (TPAD) for grappling the satellite.  Three attempts using the TPAD failed.  Apparently, ground-based drawings of the Solar Max grappling pin did not show a grommet that was installed on the actual flight hardware.  This prevented the TPAD from working correctly.

When it became evdient that the TPAD would not work, Nelson attempted to grab Solar Max by hand.  Unfortunately, this made matters worse as the satellite began tumbling about all three (3) axes.  Nelson retired to the Orbiter and Shuttle Mission Control in Houston, Texas went to work on assessing the crew’s next move.

Overnight, Solar Max controllers at Goddard Space Flight Center in Greenbelt, Maryland managed to regain control of the tumbling satellite.  In concert with this effort, Shuttle Mission Control in Houston came up with a revised plan to capture Solar Max and dock it in Challenger’s payload bay.  The idea now was to grapple the satellite using the Orbiter’s Remote Manipulator System (RMS).

On the fourth day of flight, Mission Specialist Hart successfully grappled Solar Max with the RMS and berthed it in the aft part of the Orbiter’s payload bay.  Nelson and van Hoften then went to work.  In a space walk lasting almost seven (7) hours, the astronauts skillfully changed-out a faulty attitude control system and the electronics box on the satellite’s coronograph.

Solar Max was redeployed to orbit on Day 5 of STS 41-C.  Following a 30-day checkout by Goddard flight controllers, the satellite resumed full operation.  While certainly more difficult than expected, the Solar Max repair effort was an unqualified success.  Following a mission of 6 days, 23 hours, 40 minutes and 7 seconds, Challenger safely landed at Edwards Air Force Base, California on Friday, 13 April 1984.  

The Solar Max repair mission of April 1984 set the stage for more challenging and extensive future work in space.  Indeed, three (3) successful  Hubble Telescope repair and refurbishment missions as well as construction of the International Space Station (ISS) share an important experiential linkage with the pioneering STS 41-C effort.

Posted in Aerospace, History

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