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Kaguya (SELENE)


Kaguya was directed into a controlled crash on the lunar surface at 18:25 on June 10, 2009 (UTC). It landed on the lunar nearside, at 65.5 degrees south, 80.4 east, near Gill crater.

Kaguya, formerly known as SELENE, was Japan's entry into the international fleet of spacecraft sent to the Moon in 2008 and 2009. (Others include China's Chang'e 1, India's Chandrayaan-1, and NASA's Lunar Reconnaissance Orbiter and LCROSS.) Kaguya -- named after a character in a Japanese fairy tale, a baby found in a bamboo thicket by an old couple who turns out to be a princess from the Moon -- was an ambitious mission comprising three separate spacecraft that aimed to answer many fundamental questions about the geology and geophysics of our nearest neighbor. At the same time, it returned the first high-definition movies from beyond Earth orbit, including stunning ones of Earth rising or setting over the lunar limb.

After launch, the three-ton Kaguya spacecraft transferred into an elliptical lunar orbit. As it lowered its orbit into a circular one, the Main Orbiter released two much smaller satellites, Okina and Ouna (named for the mythological adoptive parents of Kaguya), both of which are essentially orbiting radio transmitters. In the past, lunar missions consisting of single spacecraft have been unable to map the gravity field of the far side of the moon. Gravity experiments require a real-time radio link to Earth, so when a lunar orbiting spacecraft disappears behind the Moon it is impossible to acquire the necessary data. Okina (also known as the Relay satellite or Rstar) and Ouna (also known as the VRAD satellite or Vstar) permitted Kaguya to conduct gravity experiments on the far side of the Moon by relaying Kaguya's radio transmissions from the far side of the Moon to Earth in real time.

Diagram of the Kaguya spacecraft
Credit: JAXA
Other instruments on Kaguya studied the composition and topography of the lunar surface; mapped the lunar magnetic field and plasmasphere; and even conducted observations of the radiation environments of Earth, Jupiter, and Saturn.

Kaguya Facts
Launch date: September 14, 2007
Lunar orbit insertion: October 3, 2007
Mission end: June 10, 2009
Operational orbit: Main Orbiter: circular and polar, 100 kilometers (60 miles) altitude