NASA plans to mothball its infrared airborne observatory unless it can get financial help from international partners.
US President Barack Obama's proposed budget for fiscal 2015 slashes funding for the US-German project from $US84 million ($A94.17 million) to $12 million.
"Budgets are about making choices," NASA administrator Charles Bolden said.
NASA is the main backer of the Stratospheric Observatory for Infrared Astronomy (SOFIA), which scans the skies for celestial objects that give off infrared radiation, which is invisible to the human eye.
The high-flying observatory, which cost about $US1.25 billion to develop, has a history of delays and cost overruns. It made its first observations in 2010 and reached full operational capability in February.
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The two NASA centres in charge of the project, NASA Armstrong Flight Research Center in Southern California and Ames Research Center in Northern California, learnt about the proposed cut last week.
"It was a surprise to all of us," said David McBride, head of NASA Armstrong.
SOFIA consists of an 18,000-kilogram telescope that's mounted in the rear of a modified jumbo jet. During flight, a hatch opens to allow the telescope to see its targets.
Flying between 39,000 feet and 45,000 feet, SOFIA has an advantage over ground-based telescopes because it doesn't have to peer through water vapour in the atmosphere.
NASA previously said SOFIA was expected to last at least 20 years.
The observatory will continue flying through September. If there's no extra funding, then the space agency will have to put it in storage.
If it comes to that, "we lose a lot of momentum", McBride said.
NASA Ames director Pete Worden said he would fly to Germany in several weeks and planned to find a way to continue the mission.
