Astronomers are this week celebrating the 15th year in space for the Hubble space telescope - perhaps the most successful astronomy mission ever.
But the celebrations are overshadowed by uncertainty over the future of the orbiting observatory.
Nasa's 2006 budget, announced in February, effectively killed off the telescope, but the US space agency's new chief says it may yet be saved.
The Hubble team has released two special images to mark the occasion.
They are new views of two of the best-known objects Hubble has observed.
One is of the spiral galaxy M51 (also known as the whirlpool galaxy). The other shows the Eagle Nebula, a tall, dense tower of gas being sculpted by ultraviolet light from a group of massive, hot stars.
"Hubble is the best mission in Nasa's fleet," commented Steven Beckwith, director of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, US, which operates Hubble.
"It's producing beautiful science that the public loves and it makes us all look great," he told the BBC News website.
Without servicing of its fading batteries and gyroscopes, the observatory will probably stop taking pictures by 2007 or 2008. To the outrage of many astronomers, Nasa's previous administrator Sean O'Keefe cancelled all plans to repair the telescope.
But now Hubble has been thrown a lifeline: the agency's new chief, Mike Griffin, has pledged to re-visit the decision.
Speaking to the BBC News website before the appointment of Dr Griffin as Nasa administrator, Dr Beckwith said: "[Hubble] helps science, it helps other missions and it helps Nasa. So I would hope [Nasa's new administrator] could re-open the question of shuttle-based servicing or robotic servicing - either one."
Since it was launched on 24 April 1990, Hubble has produced over 700,000 images of the Universe. There is a long list of scientific achievements made by scientists using the telescope.
Hubble has helped astronomers calculate the age of the Universe (13.7 billion years old), has helped confirm the existence of dark energy and has gathered evidence that the expansion of the Universe is accelerating.