Washington - Five straight days of intense and dangerous
repair work have sharpened the vision of the Hubble Space Telescope
and prepared it to once again collect groundbreaking insights into
the origins of the universe.
The world's most famous telescope has been orbiting Earth since
1990 sending back some of the most spectacular images of galaxies. It
helped scientists to place the age of the universe at 13.7 billion
years, learn that black holes are at the centre of most galaxies,
monitor planetary formation and discover that the universe is
expanding at an ever-faster pace.
But despite its storied past, the Hubble looked set for the junk
heap until the space shuttle Atlantis' repair mission this week. New
instruments were installed and existing instruments were repaired to
extend its life until at least 2014, and possibly beyond.
NASA had originally decided against the maintenance mission
because of the risk involved and the pressures to complete
International Space Station construction by 2010, when the shuttle is
to be retired. But US politicians and world astronomers fought
successfully to keep alive the instrument that has expanded knowledge
of space.
Spacewalkers were able to complete by Monday all the upgrades that
NASA had planned despite struggling several times with tricky bolts
and screws that threatened to knock the mission off track.
The spacewalks were full of difficult manoeuvres that required
astronauts to crawl inside the telescope or remove dozens of tiny
pieces, which could have damaged their spacesuits, the shuttle or the
telescope.
'This is a really tremendous adventure that we've been on, a very
challenging mission. Hubble isn't just a satellite - it's about
humanity's quest for knowledge,' said astronaut John Grunsfeld, who
has been on three missions to Hubble.
Grunsfeld was part of the final spacewalk Monday and helped carry
out the last ever repairs to the telescope.
On Tuesday, Atlantis released Hubble back into its own orbit.
Scientists hope the new instruments and repairs will help them
learn about the gases between galaxies and take detailed pictures of
extremely distant stars.
The space telescope should begin taking images again in about
three weeks. It will first focus on known stars to align the
instruments before turning to new data. NASA hopes to publish the
first photos by September.
NASA officials on Tuesday refused to identify the first
observation targets, but said the wish list by astronomers is
extensive.
'Today begins the second Hubble revolution,' Hubble scientist Dave
Leckrone told reporters Tuesday. He stressed that the telescope's
early work had profoundly changed astronomy and would likely
contribute even more with its more advanced instruments.
Central to this week's repairs was the addition of a new camera.
The Wide Field Planetary Camera 3 will allow astronomers to see
deeper into space and to capture images across all three regions of
the light spectrum - ultraviolet, visible and near infrared.
It will allow scientists to look 'further back in time than man
ever has before, looking at the history of galaxies from infancy to
middle age and working out where we come from,' Leckrone has said.
Another new instrument, the Cosmic Origins Spectrograph, will
break up light into its components and allow astronomers to study the
large-scale structure and origins of the universe, including how
galaxies, stars and planets formed and how elements developed.
The installation of new gyroscopes to keep the telescope aligned
was one of the most difficult tasks. Astronauts Mike Massimino and
Michael Good could not get one new set of gyroscopes to fit properly
on Hubble and had to install a spare set instead.
Repairs on another spectrograph, the Space Telescope Imaging
Spectrograph, also presented headaches when a series of complicated
steps were halted by a stubborn stripped screw that caused several
hours of delay. Astronaut Massimino ultimately yanked off the piece.
Other equally critical, if less sexy repairs, included the
swapping of two 209-kilogramme battery units, the replacement of the
computer that controls the Hubble's instruments and formats
information to be sent to Earth, the replacement of insulation to
shield it from the harsh environment of space and fixing its guidance
sensors.
Atlantis is due to land at the Kennedy Space Centre in Florida on
Friday.
USA
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