Astronomers had hoped the US would allocate the estimated one billion dollars necessary to prolong the life of the satellite-based telescope, which has enabled scientists to look deep into space and unravel some of the universe's mysteries.

"Hubble is a spacecraft that is dying," said NASA comptroller Steve Moskowitz.

"We have decided that the risks associated with the Hubble servicing at this time don't merit going forward," he said.

Moskowitz said that NASA had allocated 75 million dollars in its budget for the fiscal year beginning October 2005 to plan a robotic mission to prepare the satellite for decommissioning and a safe descent into the ocean.

Since it entered into service in 1990, Hubble has established the age of the Milky Way galaxy, helped gather evidence to support the Big Bang theory and provided the first convincing proof by an optical telescope of the existence of black holes.

Astronauts have serviced Hubble four times, and many scientists hoped that a fifth service mission would be funded to enable Hubble to function to 2011. Currently, it is believed that Hubble's aging solar cells will provide enough energy to survive to 2007.

But Moskowitz said NASA's decision to cut off the satellite "was driven more by risk, not the budget."

"We'll do our best to save the science of Hubble," he said.

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