This story was updated at 8:45 p.m. EDT.
With the
successful landing Saturday of the space shuttle Discovery, NASA is gearing up
for its next mission: Saving the Hubble Space Telescope.
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.
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