Contact has been restored with a $US32.7 million ($A48.2 million) spacecraft headed to the moon to test out a lopsided lunar orbit, NASA says.
Communications with the craft were lost on Monday, after it left earth's orbit on its way to the moon, the space agency said.
The spacecraft spent nearly a week circling the globe after launching from New Zealand on June 28.
According to NASA, data shows "the spacecraft is in good health and operated safely on its own while it was out of contact with earth".
The cause of the communications drop-off is under investigation.
The 25kg satellite is the size of a microwave oven and will be the first spacecraft to try out this oval orbit, which is where NASA wants to put its Gateway outpost.
Gateway would serve as a staging point for astronauts before they descend to the lunar surface.
The orbit balances the gravities of earth and the moon and so requires little manoeuvring, and therefore fuel, and allows the satellite - or a space station - to stay in constant contact with earth.
Australian Associated Press
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