STS-117

The STS-117 mission delivered the second starboard truss segment (S3/S4) and associated energy systems to the International Space Station (ISS). Manufactured by The Boeing Company, S3/S4 is the heaviest station payload the shuttle has ever carried. The main functions of the S3/S4 truss segments are to provide electrical power and data interfaces for station's electronics and convert sunlight into electricity. They also provide active thermal protection to electrical components throughout the space station and allow the connection of platforms to store spare parts. S3/S4 segments were the second starboard addition to the ISS truss structure after the S1 truss was attached during Atlantis' STS-112 mission.