The Selenological and Engineering Explorer (Abbreviated as : SELENE), also known by its nickname as "Kaguya" is Japan's second lunar orbiter following the Hiten spacecraft. Produced by ISAS (Institute of Space and Astronautical Science), NASDA (National Space Development Agency), and manufactured by NEC Toshiba Space Systems, the spacecraft was launched via H-IIA on September 14, 2007 at 01:31:01 UTC.

The orbiter's nicknamed "Kaguya" was selected by the general public, which came from the name of a lunar princess in the ancient Japanese folktale "The Tale of the Bamboo Cutter". Its subsatellites; Rstar and Vstar were also nicknamed as "Okina" and "Ouna", which also came from the same folktale.

Its scientific objectives in the mission are to :

• Study the origins of the Moon and its geologic evolution

• Obtain information about the lunar surface environment

• Perform radio science, especially precise measurement of the Moon's gravitational field

Okina (formerly Rstar), and Ouna (formerly Vstar); are octagonal prism-shaped spacecrafts to support radio science.

The mission ended on June 10, 2009; by commanding the probe to make an impact on the lunar surface, along with Okina. Ouna in the other hand, is still in selenocentric orbit.