The shuttle mission that didn't get off the ground until its sixth scheduled launch attempt earlier this month made it home much more smoothly, landing this morning during its first opportunity to do so. Endeavour returned to Earth at 10:48 a.m. (Eastern Daylight Time), touching down at Kennedy Space Center in Florida under blue skies.

In a 16-day mission to the International Space Station (ISS), the seven-member crew of Endeavour delivered and installed the final pieces of the station's Japanese Kibo science lab. NASA now rates the ISS as 83 percent complete—only recently did it reach its design capacity of six resident crew members. With the shuttle slated to be retired next year, NASA has a packed full manifest of launches so that the ISS can be finished before the U.S. loses its capacity to send humans into orbit.

NASA will make a fifth try at launching space shuttle Endeavour this evening, after storms twice delayed attempts over the weekend. The shuttle's mission to the International Space Station (ISS) was originally slated to begin in June but was twice postponed that month due to leaks in a venting system that carries hydrogen gas away from the launch pad.

The launch of space shuttle Endeavour from Kennedy Space Center in Florida, which had been scheduled for 7:17 A.M. (Eastern Daylight Time) today, has been postponed due to a leak of hydrogen at the launch site, NASA announced early this morning. With days needed for repair, the soonest available launch opportunity for the orbiter is now June 17, but the space agency plans to launch a pair of lunar spacecraft that day from nearby Cape Canaveral Air Force Station, which poses a scheduling conflict.

In a statement, NASA said the Endeavour launch to the International Space Station was "on hold due to a leak associated with the gaseous hydrogen venting system outside the external fuel tank." A similar leak postponed the launch of space shuttle Discovery in March, which eventually lifted off safely four days later.

Two spacewalkers outside space shuttle Atlantis have begun repairing and upgrading the Hubble Space Telescope as part of the fifth and final Hubble servicing mission. The first of five spacewalks planned for the mission began at 8:52 A.M. today (Eastern Daylight Time) and was expected to take six and a half hours.

Top on the agenda was removing Hubble's Wide Field Planetary Camera 2 (WFPC2), a workhorse with more than 15 years of service. Astronauts Drew Feustel and John Grunsfeld replaced WFPC2 with the new Wide Field Camera 3 (WFC3), which will cover a broader range of the electromagnetic spectrum.

Atlantis is in its final approach to the Hubble Space Telescope, closing in for a scheduled rendezvous at 12:54 P.M. Eastern Daylight Time. After the shuttle catches up to the telescope in orbit and draws within 35 feet, astronaut Megan McArthur will maneuver the shuttle's robotic arm to grasp Hubble and pull it into Atlantis's payload bay.

Tomorrow the real work starts, with the first of five scheduled spacewalks designed to replace aging or faulty components and install two new scientific instruments on the 19-year-old observatory.

During yesterday's standard inspection of the shuttle's heat shield using boom-mounted sensors, NASA spotted some nicking near where the right wing meets the fuselage.

Astronauts aboard space shuttle Atlantis are inspecting the orbiter's heat shield for damage to ensure that the shuttle is capable of re-entering the atmosphere at the end of its servicing mission to the Hubble Space Telescope.

Atlantis's launch yesterday afternoon from Kennedy Space Center in Florida appeared uneventful. But inspection of the shuttle's underside and leading edges is now a routine procedure following the loss of Columbia in 2003, when the shuttle broke up during reentry after sustaining damage to its heat shield from a piece of falling foam insulation at launch.

Is NASA flying blind? Former NASA administrator Michael Griffin, who served under President George W. Bush and resigned when President Barack Obama took office, has taken a professorship at the University of Alabama in Huntsville. Griffin will teach mechanical and aerospace engineering in Huntsville, a hub of aerospace activity that is home to NASA's Marshall Space Flight Center. Meanwhile the space agency remains leaderless nearly three months after Griffin's resignation, with associate administrator Christopher Scolese acting as agency chief in an interim capacity.

In an editorial last week, the Orlando Sentinel called for the White House to appoint an administrator for the space agency. "NASA badly needs a leader and a plan," the op-ed said. "The future of the U.S. space program, billions of dollars, and thousands of jobs, depend on it."

In the market for a used space shuttle? You're in luck. If, that is, you happen to have a spare $42 million—and are a U.S. educational institution, federal agency, state or municipality.

NASA yesterday released info about its shuttles' post-retirement plans and put out feelers to gauge interest from potential buyers. (The shuttle program is currently scheduled to end in 2010.) The agency estimates it will cost $42 million to detoxify the fuel systems and conduct other "safing" measures, prep the orbiter for indoor display and transport it by air to its final destination. NASA says it may cost more to reach far-flung locations requiring a long-distance haul "over public roadways which may require removal of light posts and traffic signals or transport by barge over water." The shuttles, after all, have a 78-foot wingspan, about as broad as 11 Hummers.