The future of the Hubble Space Telescope hangs in the balance today in Washington as top NASA managers weigh the feasibility and risks of sending shuttle astronauts on a fifth and final servicing mission to the observatory.

Michael Griffin, the agency administrator, is scheduled to announce Tuesday, at the Goddard Space Flight Center in Greenbelt, Md., whether he’ll order the mission.

“There is talk about very little else at the moment. Everybody wants to know what’s happening,” said Matt Mountain, director of the Space Telescope Science Institute in Baltimore, which manages Hubble. “This is basically going to renew the telescope that is so very critical to us.”

If Griffin says “Go,” the mission could launch as early as 2008, providing 7,000 astronomers worldwide with five more years of access to the famous telescope – along with better instruments to explore the depths of the universe and its evolution.

But a Hubble mission would also be the only flight before the shuttle’s retirement in 2010 that could not reach the international space station in case of emergency. That scenario has worried NASA since 2003, when the shuttle Columbia was damaged by debris on liftoff and burned up during re-entry. All seven crew members perished.

Griffin has said he might support a manned Hubble repair, but only after two safe post-Columbia missions. The National Aeronautics and Space Administration has now flown the shuttle safely three times since then. The agency has also reduced the shedding of insulating foam – debris that damaged and doomed Columbia. In addition, crews have proved they can inspect and repair minor damage to their heat shields in orbit.

Boeing is a prime contractor for the space shuttle program.