Credit: MHI

A Japanese space probe bound for lunar orbit was launched early Friday on the first leg of a $480 million mission to search for answers to fundamental questions about the moon's enigmatic history.

The SELENE spacecraft flew into space bolted on the tip of an H-2A rocket, which released the 6,360-pound satellite about 45 minutes after blastoff. Japanese space agency officials declared the launch a success in a prepared statement a few hours later.

The rocket was targeting an egg-shaped orbit stretching more than 60 percent of the distance to the moon, according to the Japanese Aerospace Exploration Agency. Actual orbital figures were unavailable early Friday morning.

The launch sequence began with a fiery liftoff from Japan's Yoshinobu launch complex on Tanegashima Island at 0131:01 GMT Friday (9:31:01 p.m. EDT Thursday). Launch occurred in the late morning hours in Japan.

Plans called for SELENE to unfurl its solar panel and high gain communications antenna in the first few hours after spacecraft separation.

Credit: MHI

The Selenological and Engineering Explorer - or SELENE - is the first of four lunar explorers set for launch before the end of next year. Orbiters from China, India and the United States will soon join Kaguya at the moon.

The orbiter was nicknamed Kaguya after thousands of suggestions were submitted to JAXA by members of the public. The probe was named after a character in a popular ancient Japanese folktale.

SELENE is Japan's first probe to visit the moon since a technology demonstrator crashed into the surface in 1993.

SELENE will spend the next few weeks gradually raising its orbit during two engine firings. Scientists will also test the craft's systems to make sure they are working properly before arriving at the moon.

SELENE will fire its largest thruster to propel itself toward the moon after completing two-and-a-half circuits around Earth. The probe will slip into an initial elliptical polar orbit around the moon about 20 days after launch, according to JAXA spokesman Satoki Kurokawa.

The craft will slowly lower the apolune, or high point, of its path around the moon at an altitude of about 60 miles over the course of several weeks.

Credit: JAXA

Two daughter satellites stowed aboard SELENE for the trip to the moon will be deployed at different points during the orbital maneuvers. One of the small satellites will be released in an orbit with an apolune of about 1,500 miles, while the other will separate at a lower orbital altitude of approximately 500 miles.

Called RSAT and VRAD, the eight-sided 110-pound satellites will work in tandem with the SELENE orbiter to probe the weak gravity field on the moon's far side for the first time. The small craft will also help study the lunar ionosphere by observing radio interference.

Officials expect SELENE to arrive in its operational orbit about 40 days after launch. A comprehensive two-month checkout of the mission's 15 science payloads is planned before the orbiter begins its observation campaign.

At least ten months of science activities are scheduled for SELENE, but the mission will likely be extended if the spacecraft is still performing well late next year.

Credit: JAXA Download larger image version here

Science objectives for the mission focus on uncovering mysteries about the origin and history of the moon. The probe will also help lay the groundwork for an onslaught of upcoming lunar missions.

Precise maps of mineral concentrations across the moon could be used to corroborate theories that material broke off from Earth to form the moon as a Mars-sized object crashed into the planet about 4.5 billion years ago.

A high-definition camera aboard SELENE will record high resolution video clips of the lunar surface and images of Earth rising above the moon's horizon. The camera features a telephoto lens to provide both wide-angle and zoomed-in imagery.

The camera will record the dramatic videos and later send the imagery back to ground stations for use in public relations and outreach activities. Japanese broadcasting giant NHK provided the camera to JAXA.

Other cameras on SELENE will provide global coverage of the moon in three-dimensional stereo imagery, a first for a lunar orbiter. The visible camera will be able to spot objects 33 feet across, according to JAXA.

SELENE's radar sounder will pierce the moon's soil to help create a map of the lunar subsurface to a depth of several miles. The radar returns will provide scientists clues about previous tectonic activity.

A laser altimeter will also precisely measure the moon's topography. Information about the terrain at the moon's poles could be helpful in developing plans to construct astronomical observatories on the lunar surface, according to JAXA.

Credit: JAXA

Spectral instruments will be able to detect potentially high amounts of hydrogen near the lunar poles. Scientists consider hydrogen to be evidence of potential water ice deposits deep within large craters in the lunar polar regions.

SELENE could also contribute new information about the moon's tenuous magnetic field using a sensor mounted on the end of a 39-foot-long boom. Other instruments will collect data on the interaction between the solar wind and the moon.

JAXA officials say detailed information about the radiation environment at the moon will prove valuable in planning future human voyages.

Telescopes aboard SELENE will also focus on Earth during the mission to observe plasma scattered throughout the planet's magnetosphere.

JAXA is considering plans to mount a next-generation lunar mission, which may include a lander and rover to get a close-up look at the moon's surface. Launch of a potential follow-on mission is still at least a few years away, JAXA officials said.

The next launch for Japan's space agency is scheduled for this winter, when another H-2A rocket will haul the WINDS satellite into orbit to demonstrate Internet-based broadband satellite communication networks.