Guests use their laptop computers to "Tweet" and follow a NASA STS-127 crew presentation on Twitter at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

Canadian Space Agency Astronaut and STS-127 Mission Specialist Julie Payette answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

STS-127 Commander Mark Polansky speaks to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Photo Credit: (NASA/Paul E. Alers)

NASA Astronaut and STS-127 Mission Commander Mark Polansky, left, answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

STS-127 Commander Mark Polansky, left, looks on as crew member David Wolf answer a question during a presentation to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Photo Credit: (NASA/Paul E. Alers)

Students, including Marcus Pratt, left, and Ajani Young, second from left, pay close attention as the crew from STS-127 makes their presentation during a visit to Anne Beers Elementary school, Thursday, Sept. 24, 2009, in Washington. Photo Credit: (NASA/Paul E. Alers)

Thomas Tate, a third grade student at Anne Beers Elementary school, asks a question following a presentation by the crew of STS-127, Thursday, Sept. 24, 2009, in Washington. Photo Credit: (NASA/Paul E. Alers)

NASA Astronaut and STS-127 Mission Commander Mark Polansky, also known as @Astro_127 on Twitter, answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

NASA Astronaut and Mission Speciliast Tom Marshburn answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

Canadian Space Agency astronaut Julie Payette, a mission specialist on STS-127, talks about her experiences on the mission during a presentation at the Canadian Embassy in Washington on Tuesday, Sept. 22, 2009. Photo Credit: (NASA/Paul E. Alers)

NASA Astronaut and STS-127 Mission Commander Mark Polansky, far left, answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

NASA Astronaut and Mission Specialist Dave Wolf, center, answers questions at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (NASA/Carla Cioffi)

STS-127 Commander Mark Polansky, left, shakes hands with Canadian Ambassador to the United States Michael Wilson after presenting him with a montage as Canadian Space Agency astronaut Julie Payette, seated center, looks on, Tuesday, Sept. 22, 2009, during a visit to the Canadian Embassy in Washington. Photo Credit: (NASA/Paul E. Alers)

Canadian Space Agency astronaut Julie Payette, right, a mission specialist on STS-127, talks with two unidentified students during a visit to Anne Beers Elementary school, Thursday, Sept. 24, 2009, in Washington. Payette, along with the rest of the crew from STS-127, visited with students at the school Thursday. Photo Credit: (NASA/Paul E. Alers)

STS-127 shuttle mission crew members from left, Commander Mark Polansky, Pilot Doug Hurley, Mission Specialists Christopher Cassidy, Tom Marshburn, Dave Wolf and Julie Payette of the Canadian Space Agency, give a presentation at the NASA Tweetup event held at NASA Headquarters, September 24, 2009 in Washington. The NASA Tweetup featured a presentation and a question and answer session with the crew of the STS-127 shuttle mission to install new hardware and expand the Japanese Kibo laboratory on the International Space Station. Photo Credit: (NASA/Carla Cioffi)

Canadian Space Agency astronaut Julie Payette, a mission specialist on STS-127, at podium, speaks to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Christopher Cassidy, David Wolf, Mark Polansky, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, standing left, talks about the recent mission to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Julie Payette, Christopher Cassidy, David Wolf, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, at podium, speaks to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Christopher Cassidy, David Wolf, Julie Payette, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, at podium, speaks to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Christopher Cassidy, David Wolf, Julie Payette, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, at podium, and crew member David Wolf, standing right, answer questions from White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Christopher Cassidy, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, at podium, speaks to White House interns at the Eisenhower Executiive Office Building in Washington, Thursday, Sept. 24, 2009. Seated from left are crew members Christopher Cassidy, David Wolf, Douglas Hurley and Thomas Marshburn. Photo Credit: (NASA/Paul E. Alers)

Ajani Young, a fourth grade student at Anne Beers Elementary school, at podium, introduces the crew of STS-127 during their visit, Thursday, Sept. 24, 2009, in Washington. Seated from left are crew members, Chris Cassidy, Doug Hurley, Commander Mark Polansky, David Wolf, Tom Marshburn and Canadian Space Agency astronaut Julie Payette. Photo Credit: (NASA/Paul E. Alers)

STS-127 Commander Mark Polansky, center, speaks to students during a visit to Anne Beers Elementary school, Thursday, Sept. 24, 2009, in Washington. Polansky, along with the rest of the crew from STS-127, visited with students at the school Thursday. Seated from left are Canadian Space Agency astronaut Julie Payette, Chris Cassidy, Doug Hurley, David Wolf and Tom Marshburn. Photo Credit: (NASA/Paul E. Alers)

Students and teachers look on as STS-127 Commander Mark Polansky, seated left on stage talks about the mission to the International Space Station as other crew members Chris Cassidy, Doug Hurley, David Wolf, Tom Marshburn looks on during a visit to Anne Beers Elementary school, Thursday, Sept. 24, 2009, in Washington. Photo Credit: (NASA/Paul E. Alers)