STS-134: Endeavour’s Final Flight and the Installation of the Alpha Magnetic Spectrometer

STS-134 was NASA’s station utilization and logistics flight ULF-6. Alongside the particle-physics instrument AMS-02, it delivered Express Logistics Carrier 3 (ELC-3), providing the International Space Station with spare equipment for use after the shuttle’s retirement. The platform carried an S-band communications antenna, high-pressure gas tanks, spare parts for the Dextre manipulator, and micrometeoroid and debris shields.

Commander Mark Kelly and pilot Gregory Johnson flew the shuttle. The mission specialists were Greg Chamitoff, Michael Fincke, Andrew Feustel and Italian ESA astronaut Roberto Vittori. Flight controllers at Johnson Space Center and subsystem engineering teams supported the mission on the ground. The flight had to deliver cargo and integrate new equipment with an operating station.

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AMS-02 was supplied by an international collaboration led by Samuel Ting of the Massachusetts Institute of Technology. A permanent magnet bends charged-particle trajectories, which a nine-layer silicon tracker measures along with charge. Time-of-flight, transition-radiation and Cherenkov detectors and an electromagnetic calorimeter help distinguish cosmic-ray particles and measure their properties.

The experiment involved teams from 56 institutions in 16 countries and was assembled at CERN. By measuring cosmic rays, the instrument searches for antimatter and unusual particle components. The research requires long-term statistical accumulation; launch and installation provided an orbital platform for continued observation.

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The planned April 29 launch was scrubbed when the fuel-line heaters for Auxiliary Power Unit 1 failed to activate. The fault involved an aft load controller assembly. Ground crews replaced it, modified wiring and connectors leading to the heater group, and performed insulation and functional checks. The mission report identifies exposed wiring as the most probable initiating factor.

Endeavour lifted off from Kennedy Space Center’s Launch Pad 39A in Florida at 12:56 UTC on May 16, or 08:56 local daylight time. The following day, the crew inspected the shuttle’s thermal protection system and spacesuits. Initial contact with the station occurred at 10:13 UTC on May 18, followed by a rigid connection. The hatches between the vehicles opened at 12:36.

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On May 18, the shuttle’s robotic arm lifted ELC-3 from the payload bay and handed it to the station arm for installation on the port P3 truss. AMS-02 installation was completed at 09:34 UTC on May 19, and the instrument was activated at 09:53. Both payloads were intended to remain outside the station over the long term and required reliable power and data connections.

Feustel, Chamitoff and Fincke worked in pairs on four spacewalks on May 20, 22, 25 and 27. They retrieved MISSE-7 material-exposure samples, deployed MISSE-8, replenished ammonia coolant, lubricated a solar-array rotary joint, and installed a robotic grapple interface and external communications equipment. The first spacewalk ended early because of a fault in Chamitoff’s suit carbon-dioxide sensor, moving unfinished communications-cable work to the third. The final spacewalk also left the shuttle’s Orbiter Boom Sensor System at the station, adapting its interface for the station’s robotic arm.

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Endeavour undocked at 03:55 UTC on May 30. After flying around the station, it approached again for the Sensor Test for Orion Relative Navigation Risk Mitigation, or STORRM. Without docking again, it tested flash lidar and a docking camera in the actual orbital environment. The mission report records a closest center-of-mass separation of 955 feet, approximately 291 meters.

NASA Johnson Space Center and collaborating engineers subsequently analyzed more than 380 GB of vision-navigation-sensor data and reproduced close-range trajectories at a Lockheed Martin ground facility. Comparisons showed that the facility could reproduce returns from target reflectors relatively well, while stray reflections from other station surfaces remained difficult to simulate. The docking camera’s data recorder failed in flight, so it did not provide images during undocking and the subsequent rendezvous. Lidar data remained available for analysis.

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Endeavour’s main landing gear touched down on Kennedy Space Center’s Runway 15 at 06:34:50 UTC on June 1, after approximately 15 days, 17 hours and 38 minutes. Its final space mission was complete, while AMS-02 remained on the station and continued measuring.

In April 2013, the AMS collaboration published its first positron-fraction results, using data collected from May 19, 2011, to December 10, 2012. The paper analyzed approximately 6.8 million electron and positron events over 0.5–350 GeV, finding that the positron fraction rose with energy between approximately 10 and 250 GeV. Researchers continued collecting data to investigate the source of the high-energy positron excess.

References: [1] [3]