NASA / Frank Michaux
Space shuttle Endeavour glistens in the sun on Launch Pad 39A at NASA's Kennedy Space Center in Florida. The shuttle is launching on its final mission on May 16.
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updated 5/9/2011 5:37:42 PM ET 2011-05-09T21:37:42

NASA has officially set a May 16 launch date for the space shuttle Endeavour after more than a week of repairs to once again ready the spaceship for what will be the second-to-last mission of the agency's 30-year shuttle program.

Endeavour is now scheduled to lift off from NASA's Kennedy Space Center in Cape Canaveral, Fla., next Monday at 8:56 a.m. EDT.

NASA called off an earlier launch attempt on April 29 when technicians discovered that two heaters protecting a critical power unit had failed. Subsequent tests traced the problem to a switchbox that powers the heaters.

Engineers have since removed the suspect box, called a load control assembly, and replaced it with a new one. They also replaced about 20 feet of wiring leading to and from the switchbox.

"Right now we're in good shape, Endeavour's looking good," shuttle launch director Mike Leinbach said Monday in a news conference. "Hopefully this time the heaters will work and we'll be able to launch on time Monday morning."

Shuttle's perplexing problem
Though mission managers said they had a pretty good handle on the problem, they still haven't isolated the source of the failure to one root cause.

"The failure on launch date was a failure of having power supplied to the heaters," said Mike Moses, chair of the mission management team. "The cause of that failure to supply power, we're still not exactly sure of."

Nonetheless, the team knows enough for now to commit to a new launch date, Moses said.

"We have extremely high confidence that the problem is no longer on the ship," he added.

Endeavour's final mission
Endeavour will carry six astronauts to the International Space Station to deliver a new $2 billion astrophysics experiment that will study dark matter and other mysteries of the universe. The shuttle will also haul up a load of spare supplies for the orbiting laboratory. Four spacewalks are planned.

The shuttle's veteran crew will be led by commander Mark Kelly, whose wife, U.S. Rep. Gabrielle Giffords, is recovering after being shot in the head in January. Giffords had traveled to Florida from her rehabilitation hospital in Houston for the April 29 launch attempt, but it's uncertain whether she'll be able to make the trip back for the next liftoff date on May 16.

Kelly and the other shuttle Endeavour astronauts will arrive in Florida on May 12 to begin preparing for their launch.

Endeavour's STS-134 mission was originally slated to last 14 days, but NASA has officially extended it to a 16-day voyage to allow the astronauts to complete more get-ahead work on orbit.

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After this mission, Endeavour's 35th and final spaceflight, NASA plans only one more space shuttle launch. The shuttle Atlantis was scheduled to launch on June 28, but given the delay with Endeavour, Atlantis' launch date will also slip, Moses said.

Mission managers estimate they will have to delay Atlantis' STS-135 liftoff by about two weeks.

"I'm really sorry, but we cannot estimate that 135 date," Moses said. "We're looking at the second week of July."

After the space shuttles fly their final missions, NASA's three shuttle orbiters — Endeavour, Atlantis and Discovery — will be retired to museums.

You can follow Space.com senior writer Clara Moskowitz onTwitter @ClaraMoskowitz.Follow Space.com for the latest in space science and exploration news on Twitter@Spacedotcom and on Facebook.

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Photos: The life of space shuttle Endeavour

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  1. Special delivery

    Endeavour was the last space shuttle to join NASA's fleet: It was built to replace the shuttle Challenger, which was lost in an explosion shortly after launch in 1986. This view shows Endeavour perched atop a modified Boeing 747 on May 2, 1991, beginning the ferry flight from Palmdale, Calif. - where the shuttle was built - to Kennedy Space Center in Florida. (NASA) Back to slideshow navigation
  2. First liftoff

    Endeavour lifts off from Launch Pad 39B at NASA's Kennedy Space Center on May 7, 1992, beginning its first mission. The STS-49 mission's primary task was the repair of the Intelsat VI telecommunications satellite. Endeavour was the only shuttle to make its maiden flight from Pad 39B. (NASA) Back to slideshow navigation
  3. Grab that satellite!

    Endeavour astronauts Richard Hieb, Thomas Akers and Pierre Thuot hold onto the 4.5-ton Intelsat VI satellite after making a six-handed "capture" on May 13, 1992. The satellite failed to rise above low Earth orbit when it was launched in 1990. During Endeavour's maiden mission, astronauts retrieved the satellite, attached it to a new upper-stage booster and relaunched it to its intended geosynchronous orbit. This mission marked the first time that three people from the same spacecraft walked in space at the same time. (NASA) Back to slideshow navigation
  4. Science in space

    Endeavour astronauts Jan Davis, left, and Mae Jemison prepare to deploy the lower body negative pressure apparatus on Sept. 15, 1992. Scientific research was the main focus of this Spacelab-J mission, also known as STS-47. The mission's crew included the first African-American woman to fly in space (Mae Jemison) and the only husband-and-wife team to go into space together (Jan Davis and Mark Lee). (NASA) Back to slideshow navigation
  5. Fixing Hubble

    Astronauts flew on Endeavour to take on the first Hubble servicing mission in December 1993. In this picture, spacewalkers Story Musgrave and Jeffrey Hoffman perform an orbital ballet. The coastline of western Australia is visible below. The complex and highly successful repair mission allowed Hubble, which was launched with a defective mirror, to see into the universe with unprecedented clarity. (NASA) Back to slideshow navigation
  6. Building the station

    Endeavour spacewalker Jim Newman holds onto the International Space Station's Unity connecting module as he removes covers and works on connecting cables on Dec. 7, 1998. The STS-88 flight marked the shuttle fleet's first space station assembly mission. (AFP/Getty Images) Back to slideshow navigation
  7. Erroneous endeavor

    The shuttle Endeavour sits on its launch pad at Kennedy Space Center in Florida on July 11, 2007. "Endeavor" is spelled incorrectly on the banner. The shuttle was named after the HMS Endeavour, the British sailing ship that carried Captain James Cook on his first voyage of discovery from 1768 to 1771. That's why Endeavour reflects the British spelling of the word. (Eliot J. Schechter / Getty Images) Back to slideshow navigation
  8. Spacewalkers at work

    During the first spacewalk of the STS-118 mission, on Aug. 11, 2007, astronaut Rick Mastracchio and Canada's Dave Williams (out of frame) attach a new segment of the International Space Station's truss and retract a collapsible radiator. (NASA) Back to slideshow navigation
  9. Class portrait

    The crew members of Endeavour's STS-118 crew pose for their official portrait on Aug. 8, 2007. From left are Rick Mastracchio, Barbara Morgan, pilot Charles Hobaugh, mission commander Scott Kelly, Tracy Caldwell, Canadian astronaut Dave Williams and Alvin Drew. During this flight, Morgan became the first educator astronaut to go into orbit. In 1986, she was the backup for Christa McAuliffe, the New Hampshire teacher who died in the Challenger explosion. (NASA) Back to slideshow navigation
  10. Great view

    Endeavour spacewalker Rick Mastracchio relocates communications equipment on the International Space Station during an outing on Aug. 15, 2007. (NASA) Back to slideshow navigation
  11. A gouge in the tiles

    Tiles on the underside of the space shuttle Endeavour show evidence of damage in a photo taken on Aug. 12, 2007, using the shuttle's robotic arm and a camera-tipped extension boom. The close-up imagery helped mission managers determine that the gouge would pose no threat during Endeavour's atmospheric re-entry. (NASA via AP) Back to slideshow navigation
  12. Eye of the hurricane

    Crew members aboard the shuttle Endeavour captured this picture of Hurricane Dean's eye in the Caribbean on Aug. 18, 2007. The STS-118 mission ended on Aug. 21, one day earlier than planned, to avoid potential complications due to the storm. Forecasters worried that Hurricane Dean could have swept over Houston around the time of landing - but in the end, the storm took a different course. (NASA) Back to slideshow navigation
  13. In control

    NASA Administrator Michael Griffin watches the liftoff of the space shuttle Endeavour from the Launch Control Center at NASA's Kennedy Space Center on Nov. 14, 2008. The STS-126 mission delivered two spare bedrooms as well as a second kitchen and bathroom to the International Space Station. (Bill Ingalls / NASA) Back to slideshow navigation
  14. Repairs at the pad

    Workers perform repairs on the shuttle Endeavour's external fuel tank at the Kennedy Space Center launch pad on June 14, 2009. The launch team detected a leak of hydrogen fuel from the tank, forcing a delay in Endeavour's STS-127 launch. The mission's main task was the delivery of the final segment of Japan's Kibo laboratory to the International Space Station. (Tim Jacobs / NASA) Back to slideshow navigation
  15. Lightning strikes

    A giant bolt of lightning hits Endeavour's Florida launch pad on July 10, 2009. Technical problems and severe weather forced five delays in Endeavour's STS-127 launch. (Gene Blevins / Zuma Press) Back to slideshow navigation
  16. Liftoff at last!

    The space shuttle Endeavour rises from Kennedy Space Center's Launch Pad 39A on July 15, 2009, on the STS-127 mission's sixth launch attempt. (NASA) Back to slideshow navigation
  17. Parting glance

    The space shuttle Endeavour is photographed from the International Space Station soon after its departure on July 28, 2009. A Soyuz spacecraft docked at the station is visible in the foreground. (NASA) Back to slideshow navigation
  18. Twilight of the shuttle

    The shuttle Endeavour is silhouetted against different layers of the sunlit atmosphere during its approach to the International Space Station on Feb. 9, 2010. The primary payloads for Endeavour's STS-130 mission were the Tranquility module and the Cupola observation deck and control station. (NASA) Back to slideshow navigation
  19. Check out this view!

    Astronaut George Zamka, Endeavour's commander for the STS-130 mission, peeks out a window of the International Space Station's newly installed Cupola observation deck on Feb. 19, 2010. The Cupola provides an unparalleled view of Earth below. (NASA) Back to slideshow navigation
  20. Tanks for the memories

    The external fuel tank for Endeavour's final mission, STS-134, is transported to the Vehicle Assembly Building at the Kennedy Space Center in Florida on July 14, 2010. STS-134's main payload is the $2 billion Alpha Magnetic Spectrometer, an international physics experiment. (John Raoux / AP) Back to slideshow navigation
  21. The view from above

    The space shuttle Endeavour is lowered into place for attachment to its external fuel tank and solid rocket boosters in the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida on March 1, 2011. (NASA via Getty Images) Back to slideshow navigation
  22. Greeting the day

    The sun rises as photographers gather on a hill to take pictures shortly after the shuttle Endeavour's arrival at Kennedy Space Center's Launch Pad 39A on March 11, 2011. (Roberto Gonzalez / Getty Images) Back to slideshow navigation
  23. Into the clouds

    Photographers track the space shuttle Endeavour's ascent as it pierces the clouds and disappears after launch from NASA's Kennedy Space Center in Florida on May 16. (Craig Rubadoux / Daytona Beach News-Journal via AP) Back to slideshow navigation
  24. Godspeed, Endeavour!

    Spectators react as the space shuttle Endeavour lifts off from NASA's Kennedy Space Center in Florida on May 16. Hundreds of thousands of people watched the start of the next-to-last space shuttle flight. (Scott Audette / Reuters) Back to slideshow navigation
  25. Above the clouds

    Stefanie Gordon captured this remarkable picture of the space shuttle Endeavour rising above Florida's cloud cover on May 16 while she was on a commercial flight from New York to Palm Beach, Fla. (Stefanie Gordon / for msnbc.com) Back to slideshow navigation
  26. The last spacewalk

    NASA astronaut Greg Chamitoff holds a handrail during the fourth and last spacewalk conducted by the shuttle Endeavour's crew at the International Space Station on May 27. Chamitoff and astronaut Michael Fincke (visible in the reflections from Chamitoff's helmet visor) transferred an inspection boom system, completing U.S. assembly of the station. The May 27 outing marked the last scheduled spacewalk to be conducted by a space shuttle crew. (Nasa T.V. via EPA) Back to slideshow navigation
  27. Night passage

    Backdropped by a nighttime view of Earth and the starry sky, the space shuttle Endeavour is seen docked to the International Space Station on May 28. (NASA via Reuters) Back to slideshow navigation
  28. Landing in the dark

    The space shuttle Endeavour lands for the last time at NASA's Kennedy Space Center in Florida on June 1, 2011. The touchdown capped Endeavour's 16-day mission to deliver a $2 billion science experiment to the International Space Station on NASA's next-to-last shuttle flight. (Joe Skipper / Reuters) Back to slideshow navigation
  29. Blastoff into history

    A NASA poster pays tribute to Endeavour and its space missions over the past two decades. The shuttle is shown rising to orbit, with patches for each of its missions laid out in a spiral. The HMS Endeavour, which inspired the spaceship's name, is shown at lower right. At upper left, pictures of Endeavour are framed in the windows of the Cupola. The background image depicts the nebula NGC 602 as seen by the Hubble Space Telescope, which was first serviced by Endeavour in 1993. (NASA) Back to slideshow navigation
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