Once Canadarm2 helps to install the fourth and final set of solar array wings to the International Space Station later this month, the ISS will then surpass Venus as the brightest object in the night sky, second only to the Moon.

The Space Shuttle Discovery is set to deliver the power-generating solar panels and Starboard 6 (S6) truss segment to the ISS on the 125th mission in the Shuttle program, known as STS-119/15A (slated for launch on March 11, 2009 at 9:20 p.m. Eastern). This final piece of the Station’s backbone will bring the ISS to its full length of 102 metres (roughly the size of a Canadian football field) and will increase the quantity of electricity available for science experiments by 50 percent. This additional power also means that the Station will be closer to being ready to house a crew of 6 astronauts instead of the current three astronauts. Canadian Space Agency Astronaut Dr. Robert Thirsk will be a member of Expedition 20/21-the first 6-person Station crew set to launch in late May 2009.

Weighing in at 14 metric tons, the S6 truss segment containing the solar array wings takes up the Shuttle’s entire payload bay. On Flight Day 4, astronauts Sandra Magnus and John Phillips will use Canadarm2 to lift the S6 segment from the payload bay and hand it to the Shuttle’s Canadarm, controlled by astronauts Tony Antonelli and Joseph Acaba from inside Discovery’s aft flight deck. As Canadarm holds the truss segment, Canadarm2 will move to the worksite where it will install the S6, then reach back to grasp the truss segment from the Shuttle’s robotic arm, where it will remain parked overnight. It will take a full day to move the S6 from the Shuttle bay to its overnight position, and will require Canadarm2 to stretch out to its full length of 17 metres-a delicate maneuver with such a heavy payload. As always, Canadarm2’s operations will be monitored closely by American and Canadian flight controllers on the ground in Houston and at the Canadian Space Agency’s headquarters in Quebec.

The first of the mission’s four spacewalks will take place on Flight Day 5 to install the S6 truss segment. Spacewalkers Steve Swanson and Richard Arnold will work outside to assist John Phillips as he operates Canadarm2 from inside the Station to manoeuvre the S6 truss into place. The spacewalkers will then complete the installation of the truss segment and prepare the solar arrays for deployment. After more preparatory work during a second spacewalk on Flight Day 7, the solar panels will be deployed on Flight Day 8, which will make the Station look even brighter to stargazers around the world.