NASA's change of heart to reinstate a final, life-extending mission to the Hubble telescope is a reminder of what the Shuttle is all about

NASA has learned - perhaps relearned - a lesson during the saga of the Hubble Space Telescope: that its role as a research organisation is to inspire, and not only discover and develop.

Scientists led the campaign to restore a cancelled repair mission to extend the telescope's useful life, but it was public support for Hubble that persuaded NASA to schedule a Space Shuttle flight to service the orbiting observatory, despite the risks.

The scale of that support was a direct result of the stunning images of distant galaxies and nebulae that Hubble has produced over the years. While those images are helping scientists understand the universe, they have caught the imagination of millions, regardless of whether they care about or comprehend the physics behind these stellar phenomena.

It was not an easy decision for NASA. The planned Shuttle servicing mission was cancelled in the wake of the 2003 Columbia disaster because a rendezvous with Hubble will deny the crew the safe haven of the International Space Station. Inspecting the orbiter for damage, and if necessary repairing its thermal protection, will be more difficult without the support of the ISS.

With only three missions under its belt since return to flight, and lingering issues with foam debris, NASA has decided the Shuttle is safe enough to fly to Hubble. Damage has been mitigated and on-orbit inspection and repair techniques demonstrated. With only a few Shuttle flights left before its retirement in 2010, it was time to commit to repairing Hubble - and NASA has.

The response has been overwhelmingly positive. For some Hubble is simply too valuable an asset to allow it to fall into disrepair. For others, the final servicing mission will underline, at the twilight of its troubled life, what the Shuttle was all about. And the two have been linked from the beginning. Hubble was scheduled for a Shuttle launch in 1986, but was delayed by the Challenger disaster that year, finally being orbited in 1990 and subsequently visited four times: the first in 1993 to fix a problem with the telescope's primary mirror, then three more times between 1997 and 2002 to service and upgrade the observatory.

To fans of manned spaceflight, the images of spacewalking astronauts capturing the massive satellite, servicing it from the Shuttle payload bay, then releasing it to return to its observations, are as inspiring as the telescope's imagery - as much a glimpse into a distant future as Hubble's dramatic pictures are a look into a distant past.

And that is the lesson for NASA. Hubble's long view into deep space is integral to the public's interest in, and support for, space exploration. As the agency gets on with the solid, but dull engineering task of developing the USA's next manned spacecraft, it must not take its eye off the necessity of providing inspiration.