“Twin Grail” to arrive at the moon on New Year’s
The National Aeronautics and Space Administration (NASA) said that its twin spacecraft are on their way to arrive back-to-back at the moon after a 3½-month journey.
The Grail probes – short for Gravity Recovery and Interior Laboratory, the $496 million mission, won’t land on the moon’s surface but rather 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.
The 2½ million miles (3.22 million kilometers) voyage launched on September, took a roundabout way to save on costs by launching on a small rocket.
Once at the moon, the probes will spend the next two months modifying their positions before they start collecting data in March. The pair will fly in formation above the surface, with an average separation of 124 miles (199.55 kilometers).
The mission's chief scientist, Maria Zuber of the Massachusetts Institute of Technology, said many aspects of the moon remain a mystery despite being well studied, she added that we actually know more about Mars than we do about our own moon.
One puzzle scientists hope to solve is why the moon's far side is hillier than the side that always faces Earth. Researchers suggested that Earth once had dual moons that collided and formed the moon that people gape at today.