By Pallab Ghosh
BBC News science correspondent
The man in charge of the Hubble space telescope's science missions has appealed to Nasa's new administrator to find the money for one last servicing mission to the observatory.
Dr Stephen Beckwith told BBC News that the cost of such a mission would amount to "loose change" for the US space agency and would lead to many important scientific discoveries.
This week marks Hubble's 15th year in space. Already, its stunning pictures have transformed our understanding of the cosmos.
Among its many considerable achievements, the telescope has enabled us to work out the age of the Universe and confirm the existence of black holes.
But this remarkable piece of orbiting hardware needs regular maintenance and unless it is serviced soon, it will probably stop working in about three years' time.
Currently, Nasa is not prepared to risk a human shuttle flight to do this upgrade work and is reserving funds sufficient only to bring the telescope down safely at the end of its mission - whenever that comes.
But Dr Beckwith, the director of the Space Telescope Science Institute (STScI), which operates Hubble, believes that is a poor decision.
"Hubble's budget represents less than one-and-a-half percent of what Nasa spends yearly on space - I think it's loose change.
"I think the costs of keeping Hubble alive should not be a major factor for the agency given the high profile that Hubble has in both science and good publicity.
"Hubble is the best mission in Nasa's fleet right now. It's producing beautiful science that the public loves and it makes us all look just great."
Nasa's problem, however, is that its political priority is to develop President Bush's ambitious aim of sending people back to the Moon and then on to Mars.
So when the shuttle does return to flight, all missions will be directed to making up time in building the International Space Station - as a first step towards the human exploration of the near Solar System.
This means less money for basic science programmes. Nasa's argument has been that it should spend its more limited resources on building and sending up new observatories, such as the James Webb Telescope.
The JWT should launch early in the next decade and will concentrate on viewing the Universe at infrared wavelengths.
But Dr Beckwith argued that it was a false economy to scrap Hubble now.
"Certainly, we do want to build new missions and we will build bigger and better telescopes. The question of when you stop using a telescope is tied to whether it's still in its prime or over the hill.
"Hubble is still in its prime. In fact, with two new instruments planned for its next servicing mission, it will be better than ever once it's serviced."
Dr Beckwith feels that the telescope still has plenty of science miles left.
He sees two particularly fruitful areas of study. The first is continued observations on the expansion of the Universe and, in particular, its acceleration.
Hubble helped show that the acceleration is in response to some unknown force dubbed "dark energy". Dr Beckwith said he viewed this finding as "probably the most important discovery in physics in 100 years".
Another few years of research, he believes, and we could have very good ideas about dark energy's role in the cosmos.
Dr Beckwith also thinks Hubble is uniquely placed to search for extrasolar planets - planets outside our Solar System - and to assess their potential to support life.
"It's the only observatory that's been able to study the atmospheric chemistry of an extrasolar planet - so we're beginning to study the chemistry of these planets and that's absolutely essential to find out if life can exist on them."
But there is some hope for Hubble fans. Nasa's new administrator, Dr Mike Griffin, has promised to review the decision not to service the telescope - provided the return to flight of the shuttle proceeds according to plan.
Hubble may yet get its upgrade and its life extension.