The Mars rover Curiosity, the most sophisticated mobile science lab ever sent to another world, hurtled closer to the Red Planet on Saturday, on track "to fly through the eye of the needle" for a precise, safe landing on Sunday night, NASA officials said.
Mission control engineers at the Jet Propulsion Laboratory near Los Angeles acknowledge that delivering the one-ton, six-wheeled, nuclear-powered rover in one piece is a highly risky proposition under the best of circumstances.
But JPL's team said the spacecraft and its systems were all healthy and performing flawlessly, and that weather forecasts over the landing zone on Mars were favorable, as Curiosity streaked to within 2.8 million miles (4.5 million km) of its destination.
NASA, facing deep cuts in its science budget and struggling to regain its footing after cancellation of the space shuttle program, the agency's centerpiece for 30 years, has a lot riding on a successful Mars landing.
Mars is the chief component of NASA's long-term deep space exploration plans. Curiosity is designed primarily to search for evidence that the planet most similar to Earth may have once harboured ingredients necessary for microbial life to evolve.
After an eight-month voyage of more than 350 million miles (567 million km), engineers said they were hopeful that the rover will land precisely as planned near the foot of a tall mountain rising from the floor of a vast impact basin called Gale Crater.
"We're on target to fly through the eye of the needle," Arthur Amador, the Mars Science Laboratory mission manager, told reporters at a briefing about 36 hours before landing time.
Touchdown is scheduled for 10:31 pm Sunday Pacific time (1:31 am EDT on Monday/0531 GMT on Monday).
With Curiosity in the final stretch of its journey encased in a capsule-like shell, the spacecraft is essentially flying on automatic pilot, guided by a computer packed with pre-programmed instructions.