Fuel is running low on Cassini, but there’s enough for another four years of maneuvering. Technicians at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., have mastered the art of using Titan’s gravity to steer Cassini into new, interesting orbits. NASA hopes to send the spacecraft diving inside the majestic rings of Saturn to study their composition. The extended mission would cost about $60 million a year. But that money has not materialized in the NASA budget. If there is no funding, NASA will have to end the Cassini mission next year. For robotic spacecraft, the greatest hazard in the solar system turns out to be the NASA budget.