NASA weighs Hubble options, risks

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NASA has a few options when it comes to the future of the Hubble Space Telescope: It could perform another maintenance mission with a risk to astronauts, build a costly robotic servicer with a marginal chance for success, or just go ahead and send the telescope on its ultimate one-way journey into the Pacific Ocean.

In the safety environment after the Columbia accident, NASA is less willing to send a shuttle to Hubble. Shuttle flights are destined for the International Space Station, which can act as an emergency shelter if a problem prevents the shuttle's safe return to Earth.

NASA has studied a robotic servicer that would launch from a rocket, automatically rendezvous and dock with Hubble, and use a robotic hand to replace failed components.

The concept looks good on paper but has disadvantages, such as requiring techniques never performed by spacecraft and costing $2 billion.

Kathy Sullivan was one of the key astronauts who worked on Hubble to make it serviceable. "I'll put myself officially on the skeptical list about whether or not [a robot is] going to prove to be viable in a meaningful time frame," she said.

Engineers say Hubble won't last past 2007 because its aging batteries hold only a weak charge and its wiring has become brittle.

Hubble was designed for a 15-year life with regular servicing missions. It reaches that goal in 2005, but many non-serviceable spacecraft have far exceeded their life spans.

Hubble's predecessor, the International Ultraviolet Explorer (IUE), was launched in 1978 with a three-year life span but a goal of five years. It lasted 17 years and was shut down while still running because of a lack of funds. Innovative ground controllers kept IUE running, using software to compensate for its aging systems.

One of those adamant against another shuttle servicing mission to Hubble is outgoing NASA Administrator Sean O'Keefe. He has said he wouldn't want to put the launch team under undo pressure to squeeze safety margins to launch a shuttle to Hubble.

The National Research Council has recommended that NASA service Hubble via the shuttle in 2006.

A council report on the matter states: "The committee finds that the difference between the risk faced by the crew of a single shuttle mission to ISS -- already accepted by NASA and the nation -- and the risk faced by the crew of a single shuttle servicing mission to HST, is very small. Given the intrinsic value of a serviced Hubble and the high likelihood of success for a shuttle servicing mission, the committee judges that such a mission is worth the risk."

In any case, Hubble's ultimate fate is certain -- a fiery re-entry. A shuttle or robotic spacecraft will attach a propulsion module sending the telescope into the Earth's atmosphere so it burns up over the Pacific Ocean far from populated areas.