At 10 a.m. EDT today, the Countdown Status Briefing from Kennedy Space Center in Florida will be broadcast live on NASA TV. Providing an update will be NASA Test Director Pete Nickolenko and Shuttle Weather Officer Kathy Winters.

Later today, NASA TV will also carry the Launch Readiness Press Conference live from Kennedy. Updating the launch status and answering questions from the media will be the following: LeRoy Cain, launch integration manager; Mike Suffredini, International Space Station Program manager; Mike Leinbach, shuttle launch director; Benoit Marcotte, director of the Canadian Space Agency's Station Program; and U.S. Air Force First Lt. Kaleb Nordgren of the 45th Weather Squadron at Cape Canaveral Air Force Station. Coverage will begin at approximately 4 p.m. EDT.

The Atlantis crew arrived at NASA's Kennedy Space Center in Florida Thursday to begin final preparations for mission STS-115. Flying T-38 trainer jets, the astronauts landed at the Shuttle Landing Facility at 11:30 a.m. EDT.

Commander Brent Jett introduced the crew and spoke briefly about the upcoming mission to the International Space Station. "Speaking for myself and my fellow crewmates, I can assure you that we are ready for the challenge and we're ready to restart the assembly sequence." He added, "We have a saying back in Texas: 'It's time to walk the walk.' "

Mission Specialist Joe Tanner expressed the crew's appreciation to all the space workers who have worked tirelessly to prepare for the mission, adding, "When we climb aboard Atlantis on Sunday, we do so with confidence that the vehicle is ready, prepared by the best technicians, engineers and managers in the business."

The countdown officially began at noon EDT on Thursday, at the T-43 hour mark. The countdown includes about 36 hours of built-in hold time prior to a targeted 4:30 p.m. EDT launch on Sunday; it is the middle point in the launch window that extends for 10 minutes.

The STS-115 crew consists of Commander Brent W. Jett Jr., Pilot Christopher J. Ferguson and Mission Specialists Heidemarie M. Stefanyshyn-Piper, Joseph R. Tanner, Daniel C. Burbank and Steven G. MacLean, who represents the Canadian Space Agency.

With this mission, NASA is ready to get back to building the International Space Station, marking the first time in almost four years that a space station component has been added to the orbiting outpost. That also means the shuttle program is coming up on some of the most challenging space missions ever.

During their three spacewalks, crew members of Atlantis will install the P3/P4 integrated truss and a second set of solar arrays on the space station, doubling the station?s current ability to generate power from sunlight and adding 17.5 tons to its mass.