As
Discovery touched down at NASA's Kennedy Space Center in Florida to end a successful mission to the International Space Station, engineers were priming its sister ship Atlantis for a planned May 12 launch to overhaul Hubble in an 11-day mission fraught with risk."I think the only thing that beats a beautiful orbiter landing like this is the next launch," said NASA's deputy shuttle program manager Leroy Cain after Discovery landed at the spaceport in Cape Canaveral, Fla. "So we're looking forward to that as well."
Atlantis is poised to roll out to its seaside Pad 39A launch site on Tuesday. A separate space shuttle, the Endeavour orbiter, is being prepared to serve as a rescue ship should Atlantis suffer critical damage that would prevent the spacecraft from safely returning its seven-astronaut crew back to Earth.
Risky mission
In order to reach Hubble, Atlantis will fly in an orbit that has a higher than normal risk of orbital debris strikes for NASA shuttles, about a 1-in-185 chance. NASA's safety guidelines call for a maximum risk of a 1-in-200 chance, but officials said that they are weighing that risk against ways to offset it for the Hubble flight. They are also studying the risk of new debris caused by the Feb. 10 crash of two satellites in an orbit above Hubble's.
"We have some more discussions to have in terms of mitigations that we already plan to put in place and some other things that we might consider," Cain said.
Commanded by veteran spaceflyer Scott Altman, Atlantis' STS-125 mission to Hubble is expected to extend the iconic orbital observatory's lifespan through at least 2013 or later. Astronauts plan to perform five back-to-back spacewalks to add a new camera, replace gyroscopes and batteries, add a docking ring, as well as perform tricky repairs on equipment that was never designed to be fixed in space.
The mission has been delayed since October 2008, when a part on Hubble unexpectedly failed, prompting engineers to begin assembly a spare and add the new repair to the upcoming mission. It is the fifth and last service call on Hubble by shuttle astronauts.
Two shuttles, two launch pads
NASA space operations chief William Gerstenmaier told reporters that the agency has officially decided to use two separate shuttle launch pads, Pad 39A and Pad 39B, for Atlantis and its rescue ship.
The extra launch pad and shuttle are required because Atlantis and its crew of seven astronauts would not be able to seek refuge aboard the International Space Station if their spacecraft suffered critical damage and could not return to Earth. The Hubble Space Telescope flies in a higher and different orbit than the station, so Atlantis would not be able to reach the outpost, NASA has said.
The station can serve as a safe haven for shuttle missions like Discovery's STS-119 flight, which boosted the outpost to full power by delivering its final solar arrays, since the orbiters can return to the outpost after undocking if required.
NASA was initially considering using a single launch pad, Pad 39A, to launch Atlantis, as well as its rescue ship - if needed - in order to allow extra time for modifications to Pad 39B. That pad is being converted to launch NASA's new Ares I rocket and Orion spacecraft, with the first test flight Ares I-X slated for July.
Gerstenmaier said work crews were able to make substantial headway modifying Pad 39B, including erecting new lightning masts and an access level on the pad's fixed support structure. With that work complete, NASA officials felt it best use the launch pad to support the Hubble rescue plan.
"We think it's more of a normal plan to have the orbiter out at the pad," Gerstenmaier said. "It gives us a little bit more robustness from a crew standpoint."
Using both launch pads will likely mean a few weeks of delay for the Ares I-X launch test, which was slated for July 11, Gerstenmaier said.
Endeavour is currently expected to move from its processing hangar to NASA's cavernous Vehicle Assembly Building on April 10 to meet its external fuel tank and twin solid rocket boosters, NASA officials said. That shuttle would then roll out to the second launch pad on April 17, they added.
NASA plans to launch up to nine more shuttle missions before retiring its three-orbiter fleet in 2010.
One mission is reserved to upgrade Hubble in May, while the others are aimed at completing the International Space Station and, if funding is available, delivering the $1.5 billion Alpha Magnetic Spectrometer (AMS) physics experiment to the orbiting lab, Gerstenmaier said.
SPACE.com -- After Shuttle's Success, NASA Aims to Save Hubble
