SELENE (/ˈsɛlɪniː/; Selenological and Engineering Explorer), better known in Japan by its nickname Kaguya (かぐや), was the second Japanese lunar orbiter spacecraft following the Hiten probe.

[7] After their successful release, its sub-satellites, Rstar and Vstar, were named Okina and Ouna, also derived from characters in the tale.

[6] The mission featured three separate spacecraft: Okina (formerly Rstar) and Ouna (formerly Vstar) were octagonal prisms to support radio science.

The relay satellite impacted the lunar farside near the Mineur D crater at 19:46 JST (10:46 UTC) on February 12, 2009.

It was especially useful at the lunar limb, where the gravitational acceleration is perpendicular to the line of sight to Earth, making Doppler measurements unsuitable.

SELENE carried 13 scientific instruments "to obtain scientific data of the lunar origin and evolution and to develop the technology for the future lunar exploration":[18] Two 2.2 megapixel CCD HDTV cameras, one wide-angle and one telephoto, were also on board, primarily for public outreach.

[20] The HDTV system, developed by NHK (Japan Broadcasting Corporation), produced over 1.3 TB of video and stills over 19 months.