Japan's first lunar probe will try to determine how and when the moon was formed, and will study the behaviour of electromagnetic waves in space. (AP)

Japan's space agency has again postponed the launch of its lunar orbiter, this timebecause of poor weather conditions.

The Selenological and Engineering Explorer, or SELENE, was to launch on Thursday but, because of a lightning forecast, will instead lift off on Friday, the Japan Aerospace Exploration Agency said. The orbiter was last scheduled to launch on Aug. 17, but was delayed because condensors were improperly installedon two of its smallersatellites.

The Japanese lunar project, nicknamed Kaguya for a moon-born princess in Japanese folklore, hasracked up a price tag of$290 million and is four years behind schedule. The agency, or JAXA as it is known, said the project is the largest in scope since the U.S Apollo mission in the 1960s and 1970sand will carry out a more precise study of the moon than has been done before.

Yoshisada Takizawa, Kaguya's project manager, has said the Japanese lunar mission will yield more relevant data than Apollo because that initiative was more a part of U.S.-Sovietrivalry than a scientific exploit.

"These explorers collected a large amount of data regarding the moon and led to new discoveries," he wrote on the Kaguya website. "However, lunar exploration in those days was undertaken in the context of a race to land a man on the moon's surface and the data gathered were not intended or sufficient in support of serious research into the origin and evolution of the moon."

When it is launched, Kaguya will circulate 100 kilometres above the moon for a year and try to determine how and when it was formed. It will also study the sun's influence on the moon, as well as thebehaviour of electromagnetic waves in space.

NASA is planning a manned lunar mission, withits ownorbiter scheduled to go up next year.