This
story was updated at 12:54 p.m. EDT.
HOUSTON – Two
spacewalking astronauts resorted to "Plan C" Sunday to remove a stuck bolt on
the Hubble Space Telescope that blocked their efforts to begin the second daunting
repair of their mission: resurrecting a long-broken instrument that can sample
the atmosphere of distant alien planets.
Atlantis
astronauts Michael Massimino and Michael Good floated outside their shuttle at
9:45 a.m. EDT (1345 GMT) to resuscitate Hubble's jack-of-all-trades
spectrograph, which failed after a power failure in 2004.
NASA
expected the repair to be one the mission's most challenging tasks, primarily
because the instrument was never built to be fixed in space. Its power
supply sits behind a panel locked down by more than 117
tiny screws.
But a stuck
bolt on a handrail blocking access the panels stymied the astronauts. The handrail
had to be removed, but the bolt was stripped and two attempts failed to unscrew
it. Mission Control finally told Massimino to rip the handrail from Hubble with brute force,
shearing the bolt off. The move, Plan C, would take some serious strength,
Mission Control said.
"I think
you've got that in you," astronaut Andrew Feustel told the spacewalker from
inside Atlantis.
"I can try,"
Massimino said.
It is the
fourth of five crucial back-to-back spacewalks by Atlantis astronauts to
upgrade and repair
Hubble to extend its mission life through at least 2014. Atlantis' 11-day
mission is NASA's fifth and final flight to the iconic observatory before the
agency retires its three-orbiter fleet next year.
A vital
tool
The target
of Sunday's spacewalk - the Space Telescope Imaging Spectrograph, or STIS
- was installed on Hubble in 1997. It can pick beams of light apart into
their component wavelengths to find the chemical make-up of objects like
planets, comets and galaxies. But unlike other spectrographs, STIS can build
images, too, and was built for versatility.
"It has
many bells and whistles," Hubble's senior project scientist Dave Leckrone told
reporters here at NASA's Johnson Space Center on Saturday.
In addition
to being the first to discover the chemical composition of the atmosphere
around an extrasolar planet, the spectrograph was also the first to detect the
tell-tale signs of a supermassive
black hole in the heart of galaxy, Leckrone said. So scientists
understandably want it repaired if it's possible, he added.
Tiny
screws in space
Massimino
and Good plan to spend nearly five hours replacing the circuit board-like power
supply that sits behind a panel secured by 117 tiny screws, many of different
sizes and some which have washers. Each of those screws and washers need to be
removed (but not lost in space) in order to reach the power supply board. A
handrail must be removed as well.
"The
problem is that this thing was not supposed to be changed out in space,"
Massimino has said. "It's hard enough to change the thing out on the ground."
NASA
engineers built a custom-made capture plate with color-coded holes for each
screw size. The holes are large enough to fit over a screw and allow a
screwdriver bit in, but secure enough to lock loose screws inside so they don't
drift away. The engineers also built a new array of tools so Massimino could
tackle the intricate, hand-intensive repair while wearing a bulky spacesuit and
thick gloves.
Hubble
scientists and mission managers had confidence in the repair based on the
apparent ease of similar
repair work on the telescope's Advanced Camera for Surveys, which a
different pair of spacewalkers pulled off on Saturday.
Engineers
on Earth declared that camera repair a partial fix - but still successful -
late Saturday since it revived two of the camera's three imaging channels,
including a vital wide-field camera used by Hubble to build its trademark deep
views into the cosmos.
"I think
it's going to go extremely smoothly," Leckrone said of today's spacewalk,
adding that the astronauts also plan to install much-needed thermal insulation
on Hubble as well.
Massimino,
in particular, has practiced removing the screws on Earth exhaustively until it
became second nature, Leckrone said.
His best
time? A swift 40 minutes, mission managers said.
"That's
extraordinary," Leckrone said.
SPACE.com
is providing continuous coverage of NASA's last mission to the Hubble Space
Telescope with senior editor Tariq Malik in Houston and reporter Clara
Moskowitz in New York. Click
here for mission updates, live spacewalk coverage and SPACE.com's
live NASA TV video feed.
advertisement
