First of twin Grail satellites enters moon's orbit

Dec 31, 2011, 22:13 GMT

Washington - The first of two NASA spacecraft entered orbit around the moon on Saturday, starting off the New Year with a bang in a new mission to unveil the moon's inner secrets.

Grail-A began its first orbit shortly after 2141 GMT and its sister craft Grail B is to do the same at 2205 Sunday.

'Pop the bubbly and toast the moon! (NASA's) Grail A spacecraft is in lunar orbit,' NASA's Jet Propulsion Laboratory (JPL) in California tweeted at 2201 GMT.

While other revellers may have looked heavenward to watch fireworks on New Year's Eve, NASA scientists had more celestial duties as they tracked the twin Grail spacecraft from California.

'Our team may not get to partake in a traditional New Year's celebration, but I expect seeing our two spacecraft safely in lunar orbit should give us all the excitement and feeling of euphoria anyone in this line of work would ever need,' David Lehman, the project's manager, said earlier in the week in a statement.

The two small Grail spacecraft - which are about the size of washing machines - were launched from Cape Canaveral, Florida in September and will fly in formation above the moon's surface to map its gravity .

The craft took their time reaching the moon, which is just over 402,000 kilometres from Earth, in order to allow scientists time to get their scientific instruments up and running.

After several months to get the two spacecraft into tandem circular orbits around the moon, the craft will begin mapping its surface. By measuring variations in gravity across the moon's surface over three months, scientists hope to learn how the interior formed, which should also provide general clues about how rocky planets form.

Instruments on board measuring the two crafts' velocity will allow scientists to create a high-resolution map of the moon's gravitational field and ascertain what is going on below the surface.