JAXA said that the launch of the Selene spacecraft, which is also called KAGUYA and has been subject to delays for four years due to technical problems, was carried out by an H-IIA launch vehicle at 10.31 a.m. local time (1.31 a.m. GMT).
"The launch vehicle flew smoothly, and, at about 45 minutes and 34 seconds after liftoff, the separation of the KAGUYA was confirmed," JAXA said in a statement.
In line with plans the spacecraft will make two spins around the Earth and after 20 days it will approach the Moon and set into its orbit by the end of October.
The selenological and engineering explorer Selene is Japan's first large lunar explorer. It consists of a main orbiter and two small satellites. Once the orbiter has reached the Moon, it will be put into an orbit at an altitude of 100 kilometers (about 62 miles).
The upcoming mission is the largest lunar mission since the U.S. Apollo program. The main goal of the Japanese expedition is to examine the Moon for information on its elemental and mineralogical composition, surface and sub-surface structure, and its magnetic and gravitational fields.
The results are expected to lead to a better overall understanding of the Moon's evolution, the agency said.
