Guests use their laptop computers to "Tweet" and follow a NASA STS-125 crew presentation on Twitter at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

Scott Altman, who commanded the STS-125 mission to the Hubble Space Telescope, far left on stage, speaks during a press conference, Wednesday, Sept. 9, 2009, after astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments at NASA Headquarters in Washington. Photo Credit: (NASA/Paul E. Alers)

NASA Astronaut and STS-125 Mission Specialist Michael Good answers a question during a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

NASA Astronaut and STS-125 Mission Specialist John Grunsfeld answers a question during a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

NASA Astronaut Mike Massimino, known as "Astro_Mike" on Twitter, prepares to give a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

Scott Altman, who commanded the STS-125 mission to the Hubble Space Telescope, speaks during a press conference, Wednesday, Sept. 9, 2009, after astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments at NASA Headquarters in Washington. Photo Credit: (NASA/Paul E. Alers)

NASA AStronaut and STS-125 Mission Specialist Andrew Feustel, right, answers a question during a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

NASA Astronaut and STS-125 Mission Pilot Scott Altman prepares to give a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

NASA Astronaut Mike Massimino, known as "Astro_Mike" on Twitter, answers a question during a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

NASA Astronaut and STS-125 Mission Pilot Scott Altman answers questions at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)

STS-125 astronaut John Grunsfeld speaks during a press briefing at the new "Moving Beyond Earth," a new exhibition at the National Air and Space Museum in Washingon, Wednesday, Nov. 18, 2009. Moving Beyond Earth is an immersive exhibition that places visitors “in orbit” in the shuttle and space-station era to explore recent human spaceflight and future possibilities. Photo Credit: (NASA/Paul E. Alers)

STS-125 astronaut John Grunsfeld stands behind a display of Hubble memorabilia during a press briefing at the new "Moving Beyond Earth," a new exhibition at the National Air and Space Museum in Washingon, Wednesday, Nov. 18, 2009. Moving Beyond Earth is an immersive exhibition that places visitors “in orbit” in the shuttle and space-station era to explore recent human spaceflight and future possibilities. Photo Credit: (NASA/Paul E. Alers)

Astronaut John Grunsfeld speaks, Wednesday evening, Sept. 9, 2009, during a celebration of the Hubble Legacy at the National Air and Space Museum in Washington. Astronomers declared the Hubble Space Telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments. Grunsfeld, was a mission specialist aboard STS-125, the mission to repair the Hubble. Photo Credit: (NASA/Bill Ingalls)

STS-125 astronaut John Grunsfeld speaks during a press briefing at the new "Moving Beyond Earth," a new exhibition at the National Air and Space Museum in Washingon, Wednesday, Nov. 18, 2009. Moving Beyond Earth is an immersive exhibition that places visitors “in orbit” in the shuttle and space-station era to explore recent human spaceflight and future possibilities. Photo Credit: (NASA/Paul E. Alers)

STS-125 crew member John Grunsfeld, left, looks on as crew member Michael Massimino holds up a part that was replaced on the Hubble Space Telescope, during a press conference, Wednesday, Sept. 9, 2009, after astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments at NASA Headquarters in Washington. Photo Credit: (NASA/Paul E. Alers)

STS-125 Mission Specialist Andrew Feustel, right, shows a part from the Hubble Space Telescope to retired astronaut Loren Shriver, who flew on the Hubble deployment mission STS-31 in 1990, following a press conference, Wednesday, Sept. 9, 2009, after astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments at NASA Headquarters in Washington. Photo Credit: (NASA/Paul E. Alers)

Astronaut Scott Altman speaks, Wednesday evening, Sept. 9, 2009, during a celebration of the Hubble Legacy at the National Air and Space Museum in Washington. Altman commanded STS-125, the mission to repair the Hubble Space Telescope. Astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments. Photo Credit: (NASA/Bill Ingalls)

STS-125 astronaut Mike Massimino, speaks to a reporter on the red carpet prior to the World Premiere of "Hubble 3D", screened at the Smithsonian's Air and Space Museum Tuesday evening, March 9, 2010, in Washington. Photo Credit: (NASA/Paul E. Alers)

Astronaut Scott Altman speaks, Wednesday evening, Sept. 9, 2009, during a celebration of the Hubble Legacy at the National Air and Space Museum in Washington. Altman, commanded STS-125, the repair mission to the Hubble Space Teslescope. Astronomers declared the telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments. Photo Credit: (NASA/Bill Ingalls)

NASA STS-125 Mission Commander Scott Altman speaks at the Apollo 40th anniversary celebration held at the National Air and Space Museum, Monday, July 20, 2009 in Washington. Photo Credit: (NASA/Bill Ingalls)

STS-125 shuttle mission crew members, from left, Scott Altman, Gregory Johnson, Megan McArthur, Andrew Feustel, John Grunsfeld, Michael Good and Michael Massimino, give a presentation at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA's Twitter followers are in attendance, which featured a presentation and a question and answer session with the crew of the STS-125 shuttle mission to repair the Hubble Space Telescope. Photo Credit: (Carla Cioffi)

STS-125 crew members from left, Commander Scott Altman, Pilot Gregory Johnson, Mission Specialist Michael Good, Mission Specialist Megan McArthur, Mission Specialist John Grunsfeld, Mission Specialist Michael Massimino and Mission Specialist Andrew Feustel, are seen during a press conference, Wednesday, Sept. 9, 2009, after astronomers declared the NASA's Hubble Space Telescope a fully rejuvenated observatory with the release Wednesday of observations from four of its six operating science instruments at NASA Headquarters in Washington. Photo Credit: (NASA/Paul E. Alers)

Lori Garver, NASA Deputy Administrator, second from left, stands with members of the STS-125 crew and IMAX officials including Producer/Director Toni Myers, fifth from right, prior to the World Premiere of "Hubble 3D", screened at the Smithsonian's Air and Space Museum Tuesday evening, March 9, 2010, in Washington. Members of the STS-125 crew, dressed in their blue flight suits from left are; Mike Massimino, John Grunsfeld, Megan McArthur, Greg Johnson and Scott Altman. Photo Credit: (NASA/Paul E. Alers)

Jazz pianist and singer Diana Krall holds a montage given to her by the STS-125 space shuttle crew along with Apollo 11 Astronaut Neil Armstrong at the Apollo 40th anniversary celebration held at the National Air and Space Museum, Monday, July 20, 2009 in Washington. From left, Michael J. Massimino, Michael T. Good, Gregory C. Johnson, Andrew J. Feustel, Krall, Scott D. Altman, Neil Armstrong, John M. Grunsfeld and Megan McArthur. Photo Credit: (NASA/Bill Ingalls)