Second of twin Grail satellites enters moon's orbit

Jan 1, 2012, 22:54 GMT

Washington - The second of two NASA spacecraft entered orbit around the moon on Sunday, giving the space agency a double success as 2012 got underway.

Grail-B began its first orbit at 2344 GMT, following its sister craft, Grail-A, which entered orbit a day earlier in a new mission to unveil the moon's inner secrets.

'Cheers in JPL mission control as everything is looking good for GRAIL-B,' NASA's Jet Propulsion Laboratory tweeted after the craft orbit burn was completed. 'It's going to be a great 2012!!'

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.