The crew of Atlantis will participate in spacewalks as they add trusses to the International Space Station.
The countdown clock is ticking. If the weather holds on Wednesday, space shuttle Atlantis will rocket off from Earth at 12:28 p.m. Eastern Time. Atlantis's mission is to install new pieces onto the space station. This project has been on hold for three years since the tragic Columbia explosion in 2003. (For insight into the science of rocket launches, see It's Just Rocket Science)
There are currently three astronauts residing in the ISS. They share 425 cubic meters of living space for months at a time. The additional components being brought up to the ISS this week are designed to supply one-fourth of its power. Once the port three and four integrated truss segment is installed, it will be unfurled to nearly 240 feet in length and will generate, store, distribute, and regulate solar power for the station. The P3 segment is also designed to rotate all the truss segments on the space station so that they remain pointed at the sun, providing optimum power. The 35,000-pound payload will be installed during three spacewalks, or EVAs (extra-vehicular activities).
The space station is nearly halfway complete. The ISS, which is a multinational collaboration, will soon be receiving Japanese- and European-built laboratories that will use the additional power supplied by the P3/4 segments. The size of the ISS will eventually grow to that of a large 5-bedroom house. The truss for the station alone will eventually span 354 feet, which will make it the longest man-made object to fly in space. After STS115, fourteen more flights will be required to complete the space station.
As the ISS grows over the coming years, its brightness will grow too. The ISS may become as bright as magnitude -3, which is brighter than the brightest star in the sky (Sirius, at -1.4). In fact, only Venus and the moon would remain brighter. The ISS is already fairly bright, with magnitudes from around 2 to -1. (The lower the number, the brighter the object.) You can spot the ISS by putting in your location at heavens-above.com to find out when and where to look. The view will be even bigger and brighter while the space shuttle is docked with the station over the next week or so.
You can track the official countdown clock for STS115 at NASA's web site.
