LOS ANGELES — NASA says its twin spacecraft are now circling the moon on a mission to measure lunar gravity.
This undated artist rendering provided by NASA on Dec. 21,2011 shows the twin Grail spacecraft mapping the lunar gravity field. The two probes are scheduled to enter orbit around the moon over New Year's weekend. AP
The latest probe slipped into orbit on New Year’s Day, joining its twin, which arrived a day earlier.
The Grail spacecraft — short for Gravity Recovery and Interior Laboratory — will spend the next two months spiraling closer to the surface. In March, they will begin mapping the moon’s uneven gravity field from orbit to understand its interior down to the core.
The probes were launched in September and took a roundabout trip to the moon.