A decade after swinging into orbit around Saturn, NASA’s venerable Cassini spacecraft is still working, well beyond the four years of science the space agency had hoped to get. But the spacecraft is running low on maneuvering fuel, and its managers want to end with a scientific bang — an ambitious agenda that includes 22 orbits through a gap between the planet and its innermost ring before sending the craft on a death plunge into Saturn in 2017.

For several months, however, scientists have worried that NASA, financially squeezed like the rest of the federal government, could terminate the mission sooner.

This spring, agency officials, as they do every two years, will conduct a review of the spacecraft that have outlived their original missions. For the 2015 fiscal year, which begins Oct. 1, NASA faces particularly tough choices.

The Mars rover Curiosity, which will cost $67.6 million this year to operate, will complete its two-year primary mission in June, so money for continued roving will come out of funds dedicated to “extended missions.” For this year, that amount is $140 million, which includes $58.2 million for Cassini. Other extended missions include the Messenger spacecraft at Mercury, the Mars rover Opportunity and the Mars Reconnaissance Orbiter.