This
story was updated at 6:39 p.m. EDT.
The space
shuttle Atlantis and a crew of seven astronauts are officially set for a
planned May 11 launch to give the Hubble Space Telescope one last upgrade, NASA
announced Thursday.
After more
than half a year of delays, top shuttle mission managers found that Atlantis
and its crew are ready to overhaul
the 19-year-old Hubble for the final time. Liftoff is set for 2:01 p.m. EDT
(1801 GMT) on launch day at NASA's Kennedy Space Center in Cape Canaveral, Fla.
"We're
really looking forward to launching
on May 11," said John Shannon, NASA's shuttle program manager, in a
briefing at the Florida spaceport.
NASA announced
the official launch date after a day-long meeting at the agency's Kennedy Space
Center launch site in Florida to review the shuttle's readiness for flight. In
a NASA first, the space agency announced the shuttle launch decision via the
micro-blogging Web site Twitter.
Last
flight to Hubble
Commanded
by veteran spaceflyer Scott Altman, Atlantis and its crew are slated to launch
on an 11-day mission to Hubble. Five back-to-back spacewalks are scheduled to
add new instruments, replace broken gyroscopes and old batteries, as well as
attach a docking mechanism for a future robotic vehicle. The astronauts will
also attempt unprecedented repairs on equipment never designed to be fixed in
space.
If all goes
well, the mission will extend
Hubble's mission life through at least 2014, mission managers said. Astronauts
have not visited Hubble since 2002 and Atlantis' mission is NASA's first since adding
routine heat shield inspections following the 2003 Columbia tragedy.
"This is not
your average shuttle flight," Shannon said. "This is a different Hubble flight
than the previous Hubble repair missions."
Initially
slated to launch in October 2008, the Hubble servicing mission has been delayed
for months after a data handling unit aboard the space telescope failed
unexpectedly last year. The added chore of fixing that broken part was added to
the flight.
Mission
managers initially targeted a May 12 launch for Atlantis, but decided last week
to target an earlier liftoff in order to get at least three chances to lift off
before standing down due to launch range traffic.
NASA launched
the Hubble Space Telescope in April 1990 and has sent astronauts to repair or
upgrade the observatory four times. With the space shuttle fleet set to retire
in 2010, Atlantis' mission will be the fifth and last service call, NASA has
said.
Mike
Leinbach, NASA's shuttle launch director, said engineers plan to fix a minor radiator
ding in one of Atlantis' payload bay doors caused by a dropped tool part last
week. But the repair should not hinder the shuttle's launch plans.
"It's a
well understood repair," Leinbach said, adding that the fix should be complete
this weekend.
Rescue shuttle
on standby
NASA is
also prepared if the mission goes substantially awry. While Atlantis is in
orbit, a second space shuttle - the Endeavour orbiter - will be on standby to
launch a rescue mission in case of an emergency.
Unlike
recent shuttle missions to the International Space Station, where astronauts
can seek refuge if their orbiter suffers critical damage, Atlantis astronauts
have no such safe haven. They cannot reach the station from Hubble because the
space telescope flies in higher orbit than the orbiting lab and in a different
orbital inclination, or tilt relative to Earth's equator.
The mission
also has a slightly higher risk of damage from space debris, about a 1-in-229
chance of a critical strike. Missions to the space station have about a
1-in-300 chance of being struck, NASA officials have said. The space agency's
benchmark for space debris risk is a 1-in-200 chance of a serious hit, they
added.
Since Atlantis
cannot reach the space station from Hubble's position, Endeavour is primed to
launch within a week of a declared emergency with a sparse crew of four
astronauts.
According
to the plan, Endeavour would rendezvous with Atlantis, where the
stricken shuttle's astronauts would perform three spacewalks to abandon
ship and return home. Atlantis would then be disposed of during re-entry over
the Pacific Ocean, NASA officials have said.
Shannon
said Thursday that there's "a very low probability" that Atlantis would suffer
any damage just after launch or during the mission that would warrant launching
a rescue flight.
Atlantis is
currently scheduled to land on Friday, May 22 at the end of the Hubble mission.
Once the shuttle returns, NASA would begin preparing Endeavour for a planned
June mission to continue construction of the International Space Station.
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