Without repairs, Hubble will last only two or three more years.© NASA

The Hubble Space Telescope is about to have its death warrant signed, according to US government sources.

Officials revealed on Friday 21 January that NASA's budget for 2006 contains no cash to save the ageing telescope. Instead, it earmarks funds to decommission the instrument. President George W. Bush will present the budget proposal on 7 February, and the US Congress will then consider it.

The telescope could yet win a reprieve. Congress could insist on boosting NASA's budget to include the costs of a servicing mission, as they did last year. And NASA has enough flexibility in how it spends its US$16.2 billion budget for 2005 to devote some resources to a rescue mission.

"I led the fight to add $300 million to NASA's budget last year for a Hubble servicing mission, and I plan to lead the fight again this year," says senator Barbara Mikulski (Democrat, Maryland).

NASA spokeswoman Dolores Beasley said that the agency would make no official comment on the forthcoming budget until 7 February.

Astronomers insist that a repaired Hubble could deliver valuable science well into the next decade. Although ground-based telescopes can now see further and more clearly into the Universe than ever before, many astronomers still rely on Hubble to glimpse the most distant stars.

"Hubble remains the primary source of new information about the Universe," says Ken Pounds, an astronomer from the University of Leicester, UK. "Losing it would be a serious disappointment; Hubble is arguably the most successful astronomy mission ever."

Old and wobbly

Hubble has been orbiting the Earth since April 1990, photographing distant stars formed in the earliest stages of the Universe. But two of the six gyroscopes that stabilize the telescope no longer work, and as more fail Hubble will lose its ability to focus on a fixed point. Its batteries also need replacing before they run down, which is expected to happen in 2007 or 2008.

The debate on how to repair Hubble has lasted for more than a year. On 8 December 2004, an influential committee of the US National Academies' National Research Council recommended that NASA launch a manned rescue mission to service Hubble as soon as possible.

But outgoing NASA administrator Sean O'Keefe has always rejected a manned mission as too risky, favouring a robotic saviour instead. Each option would cost at least US$1 billion. Now it seems that Hubble's last visitor may be charged with guiding it into an orbit that brings the telescope crashing safely into the Pacific Ocean.

Shuttle diplomacy

The budget leaks, widely reported in the US media, may be an attempt by Hubble supporters in the government or NASA to put the debate firmly back in the public arena, says Pounds. The fuss could put pressure on politicians to save the popular mission, he says.

It's thought that President Bush wants to invest in manned space missions instead of repairing the Hubble.

Hubble has been serviced by the space shuttle four times in the past 15 years. A fifth mission was scrapped after the shuttle Columbia crashed on 1 February 2003, putting NASA's fleet out of commission while it made safety checks. The Discovery shuttle is expected to fly in May this year.

The shuttles will devote much of their time to completing the International Space Station, "but a lot of people feel that's a white elephant," says Pounds. The case for spending billions of dollars refurbishing the shuttle would be much stronger if it was going to be used to save Hubble, he says. 

University of Leicester, UK