Asteroid probe to test technologies

Tokyo

A compact spacecraft mission headed off last week on an ambitious return trip to retrieve tiny rock samples from an asteroid 300 million kilometres away.

The Japanese Muses-C mission is the first in which rocks are to be brought directly back from an asteroid. The mission is intended as a demonstration project for several critical technologies, including a solar-powered ion motor that will provide its main means of propulsion, and up-to-date imaging techniques to control it remotely when it lands. The craft is designed to collect a gram of rock from asteroid 1998SF36 and bring it back to Earth in 2007.

Project leader Jun'ichiro Kawaguchi of the Institute of Space and Astronautical Science (ISAS) in Sagamihara, near Tokyo, says the major goal of the mission is to convince researchers and government officials of the viability of a set of technologies for use in future sample-return missions.

"There are a lot of bodies out there in space, and we want to show people that they can be studied like this," says Kawaguchi.

Muses-C is designed to pelt the surface of asteroid 1998SF36 with steel projectiles travelling at 300 metres per second and then gather some of the dust that they kick up. Kawaguchi says one gram will be enough for studies into the substance of the asteroid. ISAS and NASA researchers plan to study the sample for a year and then make them available to other interested scientists.

The substance of the asteroids remains a mystery to scientists, who have had to depend on remote sensing imaging, such as that undertaken by NASA's NEAR-Shoemaker mission (J. Veverka et al. Nature 413, 390–393; 2001), for clues about their composition. ISAS built the 530-kg craft itself after NASA dropped plans in 2000 to send a robot with it. The mission will cost at least ¥12.7 billion (US$108 million).