Hubble Space Telescope Ready for Its Close-up

HOUSTON — The Hubble Space Telescope is poised to get avital facelift, and a final farewell, from an astronaut crew when NASA?sshuttle Atlantis launches next month.

Atlantis is on track to launch on Oct. 10 to reach theHubble Space Telescope, where its seven-astronuat crew plans to install new componentsand try unprecedented repairs on two instruments worth more than a quarter of abillion dollars.

"We have never attempted to repairinstruments in place on Hubble," said Ed Weiler, associateadministrator of NASA?s Science Mission Directorate, during a mission briefing onMonday. "This is going to be a difficult and challenging task."

But first, Atlantis must match Hubble's orbit and capturethe space telescope with a robotic arm, so that two pairs of astronauts canbegin 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 plannedHubble servicing flight, the space telescope's fate seems uncertain. Scientistscould "squeeze out two or three years, but much more than that is reallytough," Weiler noted.

However, the shuttle faces increasedhazards from micrometeorites and orbital debris at Hubble's distance morethan 300 miles above Earth among other risks.

Unlike recent shuttle missions to the International SpaceStation, the seven-person crew on Atlantis cannot retreat to the safe haven ofthat orbiting lab if their spacecraft runs into trouble. ?A four-person crew onAtlantis? sister ship Endeavour will stand ready to launch if a rescue missionbecomes necessary.

Hubble has been ready for its final overhaul ever since theColumbia tragedy of 2003 prompted the flight?s cancellation in 2004 due tosafety concerns. NASA later reinstated the manned mission after finding arobotic version untenable and successfully testing shuttle heat shield repairmethods in space. Visitsby shuttle crews have increased the space telescope's capabilities andredeemed Hubble's initial embarrassing defective main mirror after its launchin April 1990, mission managers said.

"If it were not for astronauts servicing it, the Hubblestory would be quite short," Weiler added.

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