LOS ANGELES (AP) — A NASA spacecraft has begun firing its engine to enter orbit around the moon.
If all goes as planned, it will join its twin, which has been circling the moon since New Year's Eve.
Together, the probes will embark on the first mission devoted to mapping lunar gravity.
On New Year's Day, the Grail-B spacecraft swooped over the moon's south pole and executed a 40-minute maneuver to brake into orbit.
Deep space antennas are tracking the probe's progress.