Japan's Selene moon probe, which entered lunar orbit on Oct. 4, jettisoned the first of its two 50-kilogram (110-pound) piggyback "daughter" satellites Oct. 8 as it settled down to business.

The largest spacecraft to reach the moon since Apollo 17, the three-ton orbiter is set to separate the other daughter satellite on Oct. 12, Japan time.

The already deployed Rstar and its VRAD sister will work with the mother ship to produce the first global map of the moon's gravity as an aid to designers who want to minimize fuel consumption as future spacecraft maintain their orbits over the lunar surface.

A camera mounted on top of Selene returned images of the successful separation. A separate camera set up to monitor the spacecraft's high-gain antenna has sent back images of the approaching moon as Selene moves through its lunar orbit.

Selene - nicknamed "Kaguya" for a mythical moon-born princess following a poll of the Japanese public - is just the first in an international fleet of orbiters scheduled to arrive at the moon over the next year or so.

China's Chang'e-1 is due to launch before the end of the year, followed by India's Chandrayaan-1 next April. NASA's Lunar Reconnaissance Orbiter also is scheduled to fly in 2008, when it will send its upper stage hurtling into a crater at the south pole to see if any water ice is kicked up in the impact plume.