Japanese probe misses a brief stellar encounter

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The Independent Online

After a two-and-a-half year wait, Japanese scientists have been frustrated this weekend as their attempt at a close encounter with an asteroid ended in a near miss. The Hayabusa probe came within a few feet of the Itokawa asteroid, which is 186 million miles from Earth, when ground control in Japan lost contact for about three hours. Officials plan to make another landing attempt on Friday.

Hayabusa, which means "falcon" in Japanese, is attempting to be the first probe to make a soft landing on an asteroid, collect a small sample of material and bring it back to Earth.

Analysing the dust of an asteroid could shed light on the origins of the solar system, given that these solitary rocks are considered to be left-over debris from when the planets formed.

When the probe came within 130ft of the potato-shaped asteroid late on Saturday it dropped a small object as a touchdown target. It then descended to within 56 feet, when Japan's space agency, Jaxa, lost contact.

"I don't think it landed. From an engineering point of view, we see this as a success. We definitely want to try again," said Junichiro Kawaguchi, the mission's project leader.

Toshihisa Horiguchi, a spokesman for the agency, said that the reason for the failure was unknown. "Hayabusa reached extremely close, but could not make the landing," he said.

The probe switched to auto-control, which enabled it to store data about its movements before transmitting the information to ground control, where it was later analysed.

The precise location of the probe was still unknown, but it was probably within six to 60 miles of the asteroid, Mr Horiguchi said. Officials plan to make a second attempt at landing on Friday.

Scientists were in communication with the probe and analysing data to try to calculate its exact position, but it was unclear whether there had been a technical problem, Mr Horiguchi said.

The failure to touch down on the asteroid comes after the loss of a tiny robotic lander from Hyabusa called Minera, which weighed less than a bag of sugar and was designed to take pictures of the asteroid's surface.

However, it appears that the asteroid's gravity was too weak to draw Minerva close enough to the surface and the lander now seems to be stranded in orbit around the asteroid.

Hayabusa, which was launched on 9 May 2003, is also hovering alongside the asteroid as they both travel through space at a speed of many thousands of miles per hour.

The probe is designed to come close enough to the asteroid to fire a tiny metal pellet that should disturb small amounts of dust for the probe to scoop up during a fleeting touch-down which will last no more than a second.

Once Hayabusa has captured a sample from the asteroid, its ion engine will be fired once more to send the probe on its long journey home. It is due to land in the Australian outback in June 2007.

Hayabusa, which weighs 1,100lb, has suffered from a number of problems, including a faulty positioning system and damage to its solar panels caused by a solar flare.

The Itokawa asteroid was chosen as the target for the mission because it belongs to the ubiquitous stony "S-type" objects that populate the inner solar system. Itokawa is typical of the small, rocky objects that regularly cross the path of the Earth's solar orbit.

Hyabusa's measurements have already indicated that the asteroid is probably a loose pile of rubble held together by weak gravity rather than a single, large object.

Itokawa's gravity is about 100,000 times weaker than that of the Earth and any attempt to grab a sample in the normal way would almost certainly fail, which is why the Japanese space agency has come up with the idea of firing a high-speed metal pellet at the surface.

Examining asteroid samples could help to unlock the secrets of how celestial bodies were formed because their surfaces are believed to have remained relatively unchanged over the eons, unlike those of larger bodies such the planets.