If successful it will be the first time any samples from space have been brought back since the US Apollo project gathered Moon rocks three decades ago.

The unmanned MUSES-C probe, carried by the mid-size solid-fuel M-5 rocket, was set to take off at 1:29 pm (0429 GMT) from the Kagoshima Space Centre in Uchinoura, 1,370 kilometres (850 miles) southwest of Tokyo, officials said.

The M-5, the fifth such rocket to be launched, is to deploy the probe into its "transfer orbit", which will set it off on a huge loop through the solar system's asteroid belt, some seven minutes after the lift-off.

The project, to achieve the world's first two-way trip to an asteroid, has been developed by the science and education ministry's Institute of Space and Astronautical Science (ISAS).

"This is a very ambitious probe which has gained international attention, and I earnestly hope this will be a success," Atsuko Toyama, minister for education, culture, sports, science and technology told a news conference.

If all goes well, the MUSES-C will reach the asteroid 1998SF36, 300 million kilometres (185 million miles) away from Earth, in two years' time, according to a description of the mission on ISAS' website.

The 1998SF36 is in the belt of asteroids between Mars and Jupiter, and is estimated to measure 500 metres (1,650 foot) in length.

The MUSES-C will spend some five months near the asteroid, making observations of its surface and gathering samples.

It is programmed to make three one-second touch-and-go contacts with the asteroid, during which it will fire small projectiles into its surface to smash part of it into particles and catch them in a cone-shaped funnel as they rise up in the low-gravity environment.

The probe is expected to return to Earth orbit in the summer of 2007, when it will release a re-entry capsule containing the samples. The capsule is to make a parachute-assisted landinig in an Australian desert.

Although they would weigh only one gramme (0.035 ounce) or so, the samples are expected to help scientists study how the solar system was created.

Friday's launch is a chance for ISAS to erase the humiliating failure of the last M-5 exploration in February 2000.

Japan lost a 100-million-dollar satellite after the fourth M-5 rocket went awry, triggering a drastic review of its disaster-prone space programme.

Japan started its space development programme in 1969, the year when US astronauts landed on the Moon.

The National Space Development Agency launched one of its H-2A rockets carrying Japan's first spy satellites in March. The rocket is hoped to allow Japan eventually to gain a slice of the commercial satellite launch market.

SPACE.WIRE