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"It's a great Hubble day," said Grunsfeld, a 50-year-old astronomer who
is making his third visit to the iconic science instrument, the most by
any astronaut. "Pretty cool," said
Feustel, a 43-year-old geologist and rookie astronaut, as he followed
Grunsfeld from the shuttle's airlock. "Fantastic."
The seven Atlantis astronauts rendezvoused with Hubble on Wednesday,
capturing the 13.2 meter (43 and half feet) telescope with the shuttle's
robot arm and mounting it upright in the cargo bay.
In all, five daily spacewalks are planned to extend observations by the
telescope for at least five years.
The ambitious refurbishment will upgrade the power and pointing system
with new batteries and gyroscopes and a more robust science computer.
The new Wide Field Camera-3 installed on Thursday, replaces the Wide
Field and Planetary Camera-2, a 16-year-old workhorse imager.
The new more versatile camera is capable of looking deep into the far
reaches of the cosmos for signs of the earliest star systems as well as
studying the closest planets.
The Cosmic Origins Spectrograph will join the new camera on Saturday.
The spectrograph has been developed to study the grand scale structure
of the universe as well as map the appearance and distribution of carbon
and the other chemical elements necessary for life.
In addition, the astronauts will attempt repairs to the internal
circuitry of two science instruments that experienced earlier electrical
problems.
But Thursday's outing was not problem free.
Two bolts that secured the Wide Field and Planetary Camera-2 proved
difficult to remove. The astronauts reached for an assortment of ratchet
tools before finding one with enough force to free them. The struggle
put them about 30 minutes behind schedule.
As Grunsfeld reached into a tool bag for one of the ratchets, a rivet
floated out. Grunsfeld reacted quickly by reaching out and grabbing the
fastener before it could float away.
The spacewalkers also exercised caution to avoid a dusting of a white
material spotted on a piece of of the shuttle's equipment. NASA feared
the material might contaminate the telescope's optics.
"I see a small amount of what looks like dust, but it's pretty minor,"
Fuestel assured Mission Control "Almost imperceptible."
Thursday's spacewalk includes a second high priority task, the
installation of a new science computer to replace a processor that
experienced a partial electrical failure in late September.
The breakdown of the Science Instrument Command and Data Handling System
prompted NASA to postpone plans to launch the Hubble mission in October
so engineers could prepare a replacement.
The science computer prepares each of the telescope's science
instruments for deep space observations and formats the observations for
transmission to Earth.
The third task on the first spacewalk was the installation of a new
docking system.
Although NASA has no plans for a future shuttle visit to Hubble, the new
docking device would allow a robotic spacecraft with a propulsion module
to latch onto the observatory.
When Hubble is no longer able to conduct observations, NASA plans to
steer the space telescope into the Pacific Ocean rather than allowing it
to plunge back to Earth uncontrolled, potentially endangering a
populated area.
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