CAPE CANAVERAL -- A two-armed android launched from Cape Canaveral and operated by an astronaut in Houston is emerging as the leading candidate for a robotic mission to save NASA's Hubble Space Telescope, agency officials said Tuesday.

The Canadian robot "Dextre" is shown clamped onto the Hubble telescope with its robot arm extended in this artist's rendering. Image from NASA.

Dubbed "Dextre," the Canadian robot would blast off on an Atlas 5 or Delta 4 rocket in late 2007 and then outfit the $3 billion observatory with fresh batteries and gyroscopes as well as two new $100 million science instruments.

Technical challenges still loom, and NASA must persuade the Bush administration and Congress to ante up an estimated $1 billion to $1.6 billion to pay for the mission, which is not funded in the agency's proposed 2005 budget.

But Hubble project officials are becoming more and more confident that the telescope can be serviced with robots rather than spacewalking shuttle astronauts.

"There were many skeptics, including me, when the idea of a robotic servicing mission first came up," said David Leckrone, Hubble project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "But I've become a convert."

The fate of NASA's flagship observatory has been in orbit since January.

Insisting that a shuttle mission to Hubble would be too dangerous in the wake of the 2003 Columbia accident, NASA Administrator Sean O'Keefe canceled a fifth servicing flight to the observatory. Without repairs, the telescope is expected to fail by 2007 or 2008.

An outcry from the public, scientists and members of Congress prompted NASA to examine the possibility of a robotic servicing mission. The agency came up with a scheme, fielded additional ideas from industry and began in-house tests.

In a series of long-distance tests, NASA astronaut Michael Massimino has been sitting at a control console in Houston and operating a prototype robot in Maryland. The idea is to practice work that would have to be done on an unmanned servicing flight.

Those tests and others convinced O'Keefe this week to tell Hubble project engineers to press ahead with development work.

"He was very impressed with the work that had been done to flesh out the robotic servicing option," NASA science mission chief Al Diaz said.

The aim now is to determine by next summer whether a robotic mission could be carried out successfully -- and in time.

If not, NASA instead will launch a propulsion module that would autonomously link up with Hubble and propel it back through the atmosphere and into the Pacific Ocean.

The 13-ton observatory lacks its own propulsion system. Without a propulsion module to control the telescope's re-entry, surviving Hubble debris could rain down on populated areas.

Leckrone, Diaz and others, however, now think a full up robotic servicing mission could work. Here's how such a flight might unfold:

• NASA would launch a 12,000- to 15,000-pound spacecraft consisting of a propulsion module and an ejection module. The ejection module would contain bays for two new Hubble instruments as well as the two-armed android and a smaller version of a shuttle robot arm.

• The shuttle-like arm would maneuver the two-armed robot -- a copy of which is being developed by the Canadian Space Agency for the International Space Station -- to work sites on the four-story observatory.

• Also known as the Special Purpose Dexterous Manipulator, or SPDM, the robot then would remove old Hubble instruments and stow them in ejection module bays.

• The two new instruments -- the Wide-Field Camera-3 and the Cosmic Origins Spectrograph -- then would be installed.

A new set of gyroscopes would piggyback on the planetary camera. Fresh batteries would be mounted on the tail end of the propulsion module and then the robot would wire them up to the telescope's power-producing solar wings.

Both Leckrone and Diaz said a robotic servicing mission would keep Hubble operating an extra five years. That's roughly when its successor, the James Webb Space Telescope, is launched in 2011 or 2012.

And project officials said it also would help NASA develop the type of technologies that eventually will be needed to carry out future human and robotic missions beyond Earth orbit.

"I love the shuttle servicing missions, and they've been wonderful for the telescope. But another shuttle mission would be the end of an era," Leckrone said. "This (robotic) mission would be the beginning of a new era in robotic technology."

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