When
astronauts overhaul the Hubble Space Telescope this summer, they will leave
behind a vastly more powerful orbital observatory to scan the universe.
Set to
launch aboard NASA's shuttle Atlantis on Aug. 7, the Hubble servicing mission
will be the fifth — and final — sortie to upgrade
the aging space telescope.
"We're not
only going up to Hubble to refurbish it, but also to expand its grasp
tremendously," said Alan Stern, associate administrator for NASA's science
mission directorate, in a recent briefing. "We expect to make the very best
discoveries of the entire two-decade plus Hubble program with the new
instruments to be installed."
A deeper
look
In addition
to performing vital repairs, astronauts will add
two new instruments to Hubble's observation platform — Wide Field Camera-3
and the Cosmic Origins Spectrograph — that will drastically boost its vision
range.
"This
refurbished Hubble [will be] a new telescope," said astronomer Sandra Faber of
the University of California, Santa Cruz. "We estimate that at the end of this
repair Hubble will be 90 times more powerful than when it was first launched."
That means
that Hubble will be able to see at least 90 times more objects in deep space
than it could when it was deployed in April 1990, she added.
With its
ability to scan the universe at wavelengths ranging from the near-infrared,
visible spectrum to the near-ultraviolet, the new Wide Field Camera-3 should
allow Hubble to see objects that formed fewer than 800 million years after the
beginning of the universe.
"To follow
galaxy formation to times that are even earlier than this, we need a camera
that can take sharp pictures efficiently at longer wavelengths," Faber said.
"And that's exactly what Wide Field Camera-3 is going to do."
The new
camera has better resolution than its Wide Field Planetary Camera-2 predecessor
and a wider field of view than Hubble's current NICMOS spectrometer, and could
reveal objects that formed when the universe was just 400 or 500 million years
old, she added.
"A
difference like this makes a huge difference in the structure and formation of
the galaxies that we'll see," Faber said. Astronomers currently estimate that
the universe is about 13.7 billion years old.
Hubble's
new Cosmic Origins Spectrograph, meanwhile, will scan the universe in the
ultraviolet range with about 10 times more sensitivity than the observatory's
current tools.
"I believe
it's the most sensitive UV spectroscopic capability ever to fly in space for
astronomical purposes," said Hubble senior project scientist David Leckrone of
NASA's Goddard Space Flight Center in Maryland. "It's designed, because it's so
sensitive, to go as deep as possible out across the universe as fast as
possible."
Researchers
hope the new spectrograph will map the so-called
cosmic web, the universe's large-scale structure made up of strands of
galaxies that branch out in three dimensions like an astronomical spider's web.
"It is
amazing to me how we've been able to reinvent the Hubble Space Telescope with
each of these missions," said astronaut John Grunsfeld, who will serve as the
lead spacewalker for the telescope's last overhaul.
Full
power ahead
Hubble
service astronauts will also replace failed gyroscopes, fine guidance sensor
and aged batteries, and make unprecedented repairs to the space telescope's
main camera and a vital spectrograph.
"When the
astronauts leave Hubble for the last time, it will be at the apex of its
capabilities," said Leckrone. "It will be the first time since 1993 that there
will be five working instruments aboard."
Spacewalkers
will replace Hubble's cracked thermal insulation and replace each of its
16-year-old batteries among other hardware.
They will
also repair the observatory's Space Telescope Imaging Spectroscope and the
Advanced Camera for Surveys (ACS), both of which were never designed to be
fixed in orbit. Spacewalkers will remove more than 111 tiny screws to repair
the two units.
"The good
news is we're going to try and repair ACS. The bad news is we've never done it
before," said Grunsfeld. "It's very tricky."
Grunsfeld
and his six crewmates plan to stage five spacewalks to service Hubble during their STS-125
mission. NASA initially canceled the spaceflight following the 2003 Columbia tragedy, but later reinstated the mission after a detailed risk analysis.
The result,
researchers said, is about five extra years of science for Hubble before its
controlled deorbit sometime after 2020. To prepare for the space telescope's
eventual demise, spacewalkers will also attach a connecting port that will
allow a robotic tug to dock with Hubble.
"None of us
could have imagined what this fourth-generation suite of instruments can do," said
Stern, adding the 90-fold jump in observation power for Hubble will be
unprecedented. "We will have the capability, literally, of approximately 100
Hubbles [circa] 1990 when this mission is done."
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