STS-115 was a Space Shuttle mission to the International Space Station (ISS) flown by . It was the first assembly mission to the ISS after the Columbia disaster, following the two successful Return to Flight missions, STS-114 and STS-121. STS-115 launched from LC-39B at the Kennedy Space Center on September 9, 2006, at 11:14:55 EDT (15:14:55 UTC). The mission is also referred to as ISS-12A by the ISS program. The mission delivered the second port-side truss segment (ITS P3/P4), a pair of solar arrays (2A and 4A), and batteries. A total of three spacewalks were performed, during which the crew connected the systems on the installed trusses, prepared them for deployment, and did other maintenance work on the station. STS-115 was originally scheduled to launch in April 2003. The Columbia accident in February 2003 pushed the date back to August 27, 2006, which was again moved back for various reasons, including a threat from Tropical Storm Ernesto and the strongest lightning strike to ever hit an occupied shuttle launchpad. Crew Note:The P3/P4 Truss segment and batteries were so heavy (more than 17.5 short tons, or roughly 16 metric tons) that the crew count was reduced from seven to six. Crew notes Canadian Space Agency astronaut MacLean became the first Canadian to operate Canadarm2 and its Mobile Base in space as he was handed a new set of solar arrays from Ferguson and Burbank controlling the original Canadian robotic arm, the Canadarm. MacLean performed a spacewalk, becoming only the second Canadian, after Chris Hadfield to do so. The mission patch worn on the clothing used by the astronauts of STS-115 was designed by Graham Huber, Peter Hui, and Gigi Lui, three students at York University in Toronto, Ontario, the same university that Steve MacLean attended. The students also designed Steve MacLean's personal patch for this mission. Mission payloads The primary payload was the second left-side ITS P3/P4 Truss segment, a pair of solar arrays, and associated batteries. Mission objectives Delivery and installation of two truss segments (P3 and P4) Delivery and deployment of two new solar arrays (4A and 2A) Perform three spacewalks to connect truss segments, remove restraints on solar arrays, and prepare the station for the next assembly mission by STS-116 Mission background NASA managers decided to move the STS-115 launch date forward to August 27 to obtain better lighting conditions to photograph the external tank. This occurred before