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. Both S3/S4 were handed off to NASA in September 2002. S3/S3 measures long by wide by high and weighs 35,678 lbs (16,183 kilograms). It is made from stainless steel. During flight day 4 activities, the S3/S4 truss segment was removed from the payload bay of Atlantis using the shuttle's robotic arm and handed off to the station's Canadarm2, where it was maneuvered and mated to the outboard end of the S1 truss. Starboard 3 The S3 primary structure is made of a hexagonal-shaped stainless steel structure and includes four bulkheads and six longerons, beams that connect the bulkheads. The secondary structure includes brackets, fittings, attach platforms, EVA activity equipment and miscellaneous mechanisms. S3 was delivered to the Space Station Processing Facility at Kennedy Space Center on December 7, 2000. The major S3 subsystems include the Solar Array Rotary Joint (SARJ) – which contains large bearings, Segment-to-Segment Attach System (SSAS) and Payload Attach System (PAS). The SARJ continuously rotates to keep the Solar Array Wings (SAWs) on S4 and S6 (launched on shuttle mission STS‐119 in March 2009) oriented toward the sun as the ISS orbits the Earth. The S3 also provides a passive attachment point to the S1 segment via the SSAS. The PAS allows platforms to be attached to S3 for the storage of additional science payloads or spare Orbital Replacement units (ORUs). Starboard 4 Major subsystems of the S4 truss are the port inboard Photovoltaic Module (PVM), the Photovoltaic Radiator (PVR), the Alpha Joint Interface Structure (AJIS) and the Modified Rocketdyne Truss Attachment System (MRTAS). The primary functions of the PVMs are to collect, convert, store and distribute electrical power to loads within the segment and to other station segments. There are two SAWs on the S4 each deployed in the opposite direction from each other. Each SAW is made up of two solar blankets mounted to a common mast (made from shape memory alloy) and measures . In addition to the SARJ, the SAWs also are oriented by the Beta Gimbal Assembly (BGA), which can change the pitch of the wings by spinning the solar array. The PVR is deployable on orbit and is capable of dissipating