Nasa is halting all space shuttle missions to service the Hubble Space Telescope - a move which will put it out of action within four years.
Without the shuttle, Hubble will last only a few years
A safety regime being brought in for space shuttle flights in the light of the Columbia disaster rules out any further missions to service Hubble.
"This is a sad day," said Nasa's chief scientist John Grunsfeld, but "the best thing for the space community".
Hubble has revolutionised the study of astronomy since its launch in 1990.
It has sent a steady stream of striking images of space back to Earth from its orbit.
The announcement that the telescope would be left to degrade comes as astronomers revealed details of a new image produced by Hubble of the deepest view ever of the cosmos, detecting the youngest and most distant galaxies ever seen.
The image - the result of an unprecedented long look of 80 days at just one patch of sky - will be released in February and will be a major advance in our understanding of the cosmos, says BBC's News Online's science editor, Dr David Whitehouse.
Son of Hubble?
The shuttle is also gradually being wound down, and all remaining flights until it goes out of service in 2010 will be used to complete the International Space Station.
MAJOR HUBBLE SUCCESSES
Scientists say Hubble captured the "best ever" image of Mars
Gave us the age of the Universe
Provided proof of black holes
Gave first views of star birth
Showed how stars die
Caught spectacular views of Comet Shoemaker-Levy 9's collision with Jupiter
Confirmed that quasars are galactic nuclei powered by black holes
Gathered evidence that the expansion of the Universe is accelerating
Servicing missions are required to the Hubble every few years to replace worn-out parts. Flights have been halted since the explosion of the Columbia shuttle a year ago, delaying replacement of the telescope's ailing gyroscopes.
Dr Whitehouse notes that missions to Hubble are unfeasible under the US space agency's (Nasa) new post-Columbia safety procedures as it is in a difficult orbit.
Without such maintenance, Hubble should continue operating until 2008 but would eventually come back to Earth in about 2011, Mr Grunsfeld said.
"We will get as much life as we can out of the Hubble telescope, and we will continue to support research and analysis even after re-entry," he said.
The images it has beamed back to Earth have determined the age of the Universe - over 13 billion years old - and discovered that a mysterious energy is causing all of the objects in the cosmos to move apart ever quicker.
The space agency was already planning to replace Hubble with a new, improved telescope in 2011, but it is unclear whether that project will be affected.