The New Year’s countdown to the moon has begun.
NASA said Wednesday that its twin spacecraft were on course to arrive back-to-back at the moon after a 3½-month journey.
“We’re on our way there,” said project manager David Lehman of the NASA Jet Propulsion Laboratory, which manages the $496 million mission.
The Grail probes — short for Gravity Recovery And Interior Laboratory — won’t land on the lunar surface. Instead, they were poised to slip into orbit to study the uneven lunar gravity field.
Grail-A was scheduled to arrive on New Year’s Eve, followed by Grail-B on New Year’s Day.
Lehman said team members won’t celebrate until both probes are safely in orbit.