Target Moon: Japan's Kaguya Probe Set for Lunar Mission
This artist's interpretation shows Japan's Kaguya satellite in lunar orbit after jettisoning one of its smaller satellites.
Credit: JAXA/Akihiro Ikeshita.

Japan's massive Kaguya lunar orbiter stands poised to launch spaceward this week on a mission that, researchers hope, will unlock the secrets of the moon.

Equipped with a veritable arsenal of science instruments and two baby satellites, the three-ton moon probe is set to liftoff from Japan early Friday (Local Time) on a one-year mission to Earth's nearest neighbor. ?

"The Japanese people are very interested in this mission," said Shinichi Sobue, Kaguya's science coordinator and public outreach for the Japan Aerospace Exploration Agency (JAXA). "Kaguya, or SELENE, is our first mission for really observing the moon."

Japan launched a previous lunar mission in 1990, but the flight served primarily as a technology demonstrator, Sobue told SPACE.com. That mission -- dubbed Muses-A -- sent the Hiten spacecraft on a series of lunar flybys and orbits, released the small microsatellite Hagoromo and intentionally crashed into the moon's surface in 1993.

Kaguya's SELenological and ENgineering Explorer (SELENE) mission, meanwhile, is designed for in-depth lunar study. The probe is slated to lift off atop an H-2A rocket from Japan's Tanegashima Space Center on Sept. 13 at 9:31 p.m. EDT (0131 Sept. 14 GMT), though it will be Friday morning at the island launch site.

The 55 billion yen (about $480 million) mission was postponed by 24 hours on Tuesday due to bad weather. It has also been plagued by a series of other delays -- most-recently due to improperly installed condensers on its passenger satellites -- throughout its eight-year development, JAXA officials have said.

Hefty probe, heftier science

Touted by JAXA as the largest lunar mission since NASA's manned Apollo flights, Kaguya is named after a moon princess in a Japanese folktale and carries 14 primary science instruments to map the lunar surface and study its composition, subsurface and gravity field.

"Through these research activities, it is hoped that we can get closer to the core of the mystery of the origin and evolution of the moon," Kaguya's SELENE project manager Yoshisada Takizawa has said in a JAXA Web site statement.

The 6,000-pound (2,271-kilogram) Kaguya spacecraft is a nearly seven-foot (2.1-meter) wide box that stands almost 16 feet (4.8 meters) tall. The probe's X-ray and Gamma-ray spectrometers will track the distribution of elements on the lunar surface such as hydrogen, which researchers hope will help aid in the search for water ice on the moon, Sobue said.

Other instrument suites will study mineral distribution on the moon's surface; use cameras, radar and lasers to catalogue lunar terrain and subsurface structure; and probe the moon's ionosphere and magnetic field. A high-definition camera is also launching aboard Kaguya, but is destined for a more aesthetic purpose.

"The Japanese people would like to see the very beautiful, high-definition movies of the Earth rising" over the moon, Sobue said.

Atop the orbiter sit the relay (RSAT) and VRAD microsatellites, two solar-powered probes about three feet (one meter) in diameter. Kaguya will jettison the 110-pound (50-kilogram) probes as it enters lunar orbit. The two satellites are designed to then work together with their mothership to generate a complete global map of the moon's gravitational field. VRAD will also probe the moon's thin ionosphere, JAXA officials said.

"It's the first [mission] ever to study the gravity field of the far side of the moon," Sobue said of Kaguya's mission. "The data accumulated by SELENE should serve as a basis for mankind's future utilization of the moon."

JAXA mission scientists already plan to share Kaguya's gravity field measurements with NASA researchers as the U.S. space agency prepares to launch its own mission - the Lunar Reconnaissance Orbiter (LRO) - in 2008 and return astronauts to the moon by 2020, Sobue said.

Japan, too, hopes to work with international partners to develop a lunar base as part the agency's strategic vision 2025, he added.

"Thus, Kaguya will also contribute to the manned exploration of the moon," Takizawa stated.

Fly us to the moon

After launch, Kaguya is expected to orbit Earth about 2.5 times before beginning the five-day trek to the moon, Sobue said.

The spacecraft is designed to enter into a polar lunar orbit, and then deploy the RSAT and VRAD microsatellite before ultimately settling into a 62-mile (100-kilometer) high orbit around the moon. The probe's one-year science mission should begin in earnest after a three-month checkout period, Sobue said.

Kaguya is the first of series of new spacecraft bound for the moon over the next two years.

China plans to launch its first moon shot Chang'e-1 sometime later this year, with NASA's LRO and India's Chandrayaan-1 spacecraft set to fly in 2008. Japan also plans to follow Kaguya's flight with more ambitious missions under the SELENE banner, JAXA officials said.

"[W]e will plan to have SELENE follow-on missions for moon landing and sample return," Sobue said.

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