The rocket carrying the three-metric ton orbiter took off into blue skies, leaving a huge trail of vapor over the tiny island of Tanegashima, about 1,000 km (620 miles) south of Tokyo, at 10:31 a.m. (9:31 p.m. EDT) as it headed out over the Pacific Ocean.
The long-delayed lunar explorer separated from the rocket in skies near Chile about 45 minutes after lift off. It is to orbit the Earth twice and then travel 380,000 km (237,500 miles) to the moon.
"Kaguya separated from the rocket smoothly," the space agency’s launch commentator said in a live broadcast of the launch on the Japanese space agency’s Web site (www.jaxa.jp).
"Now the satellites are flying on their own. This is the first step and I am really impressed," said Tatsuaki Okada, a scientist involved in the project.
Japanese scientists say the 55 billion yen ($479 million) Selenological and Engineering Explorer, or SELENE, is the world’s most technically complex mission to the moon since the U.S. Apollo program decades ago.
"If we succeed in this program, we will be able to prove that Japan has the technology," Okada said.
The mission consists of a main orbiter and two baby satellites equipped with 14 observation instruments designed to examine surface terrain, gravity and other features for clues on the origin and evolution of the moon.
The rocket itself was built by Mitsubishi Heavy Industries Ltd.
The Japan Aerospace Exploration Agency (JAXA) has said it hopes to send astronauts to the moon by 2025, although Japan has not yet attempted manned space flight.
SELENE also carries a high-definition television camera to shoot the Earth "rising" from the Moon’s horizon, footage of which will be sent back to Earth. SELENE will orbit the moon for about a year until it runs out of fuel.
The launch is about four years behind schedule due to rocket failures and technical glitches.
China plans to launch a lunar orbiter called Chang’e One in the second half of this year to take 3D images, and it aims to land an unmanned vehicle on the moon by 2010.
India is planning its first unmanned mission to orbit the moon in 2008, powered by a locally built rocket. It is also discussing sending a person to the moon by 2020.
The United States plans to launch a lunar orbiter next year.
Japan’s space program was in tatters in the late 1990s after two unsuccessful launches of a previous rocket, the H-2.
Disaster followed in 2003 when Japan had to destroy an H-2A rocket carrying two spy satellites minutes after launch as it veered off course.