HOUSTON — The Hubble Space Telescope is poised to get a
vital facelift, and a final farewell, from an astronaut crew when NASA's
shuttle Atlantis launches next month.
Atlantis is on track to launch on Oct. 10 to reach the
Hubble Space Telescope, where its seven-astronuat crew plans to install new components
and try unprecedented repairs on two instruments worth more than a quarter of a
billion dollars.
"We have never attempted to repair
instruments in place on Hubble," said Ed Weiler, associate
administrator of NASA's Science Mission Directorate, during a mission briefing on
Monday. "This is going to be a difficult and challenging task."
But first, Atlantis must match Hubble's orbit and capture
the space telescope with a robotic arm, so that two pairs of astronauts can
begin a series of five intensive spacewalks in five consecutive days.
The upgrades and repairs include:
- Installing the Wide Field Camera 3 (WFC3) — A new and more
powerful main camera that bests its predecessors by seeing in both
ultraviolet and near infrared as well as visible light. Hubble would be
able to see 90
times more objects than it did at launch in April 1990.
- Replacing six Rate Sensor Units (RSU) — The gyroscopes
help keep Hubble pointed precisely at distant stars and galaxies for hours
at a time. Hubble can technically limp by on two or even one gyroscope,
but the fresh exchange ensures that the science keeps flowing.
- Replacing six Nickel Hydrogen Batteries — The suitcase -sized
batteries get swapped out for the first time in 16 years, giving Hubble an
extra lease on life for the next 5 to 10 years. The batteries keep Hubble
humming during the night portion of its orbit.
- Adding the Cosmic Origins Spectrograph (COS) — This
instrument uses the ultraviolet range to find out the temperature,
density, chemical composition and velocity of intergalactic gas and
galaxies, with ten times the sensitivity of current Hubble instruments.
- Repairing the Space Telescope Imaging Spectrometer (STIS) —
A two-sided instrument that uniquely scans across all light wavelengths of
objects such as planets, comets, stars and galaxies. Spacewalkers will
replace a failed power converter to restore one side of the damaged device.
- Replacing the Fine Guidance Sensor (FGS) — One of three
optical sensors that help Hubble lock onto targets with a system of
mirrors and lenses. The old FGS returns home after being removed from
Hubble during an earlier servicing mission.
- Fixing the Advance Camera for Surveys (ACS) — A highly
efficient survey tool with a wide field of view that became damaged. Astronauts
hope to repair some of its capabilities since it failed last year.
- Adding new Thermal Insulation — The multilayer insulation
on Hubble has become torn and broken by the harsh environment of space.
The new thermal blankets protect the damaged insulation and helps maintain
a steady temperature for Hubble.
Without the coming makeover, NASA's fifth and final planned
Hubble servicing flight, the space telescope's fate seems uncertain. Scientists
could "squeeze out two or three years, but much more than that is really
tough," Weiler noted.
However, the shuttle faces increased
hazards from micrometeorites and orbital debris at Hubble's distance more
than 300 miles above Earth among other risks.
Unlike recent shuttle missions to the International Space
Station, the seven-person crew on Atlantis cannot retreat to the safe haven of
that orbiting lab if their spacecraft runs into trouble. A four-person crew on
Atlantis' sister ship Endeavour will stand ready to launch if a rescue mission
becomes necessary.
Hubble has been ready for its final overhaul ever since the
Columbia tragedy of 2003 prompted the flight's cancellation in 2004 due to
safety concerns. NASA later reinstated the manned mission after finding a
robotic version untenable and successfully testing shuttle heat shield repair
methods in space. Visits
by shuttle crews have increased the space telescope's capabilities and
redeemed Hubble's initial embarrassing defective main mirror after its launch
in April 1990, mission managers said.
"If it were not for astronauts servicing it, the Hubble
story would be quite short," Weiler added.
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