SF
Gate: A pair of spacecraft known as
Grail-A and
Grail-B are set to enter orbit around the Moon over
the New Year’s weekend. They launched from the Florida
coast in September and are independently traveling to their
destination. Over the next two months they will fly in
formation around the Moon until they’re approximately 56
kilometers above the lunar surface and about 200 kilometers
apart. At that point, regional changes in the Moon’s
gravity field will cause them to accelerate or slow down, which
will change the distance between them; the changes in distance
will allow mapping of the gravity field. With that information,
it will be possible to deduce features at or below the
Moon’s surface and may help explain why the far side of
the Moon is more rugged than the side that faces Earth.
