Planetary News ARCHIVE

Hayabusa Spacecraft Arrives at Asteroid Itokawa

Hayabusa, approaching Itokawa(Artist concept)

Courtesy:JAXA/ISAS

After 850-day and more than 320,000,000-kilometer journey, Hayabusa spacecraft arrived at Asteroid Itokawa at 10:00a.m., September 12, 2005 (JST). The spacecraft is now hovering around 20 kilometers away from Itokawa. Hayabusa is the first one in history to collect and return to Earth the surface materials of an asteroid. This sample return mission is second next to US and USSR that brought back lunar surface materials during the period between late in 60’s through 70’s.

MUSES-C, pre-launching name of the asteroid explorer, was launched on May 9, 2003 aboard the upgraded four-stage MV-5 rocket from the Space Center in Kagoshima, the southernmost prefecture of mainland Japan. MUSES stands for the Space Engineering Spacecraft aboard Mu rocket and C means the third mission of this series.

The targeted asteroid was discovered in 1998 and tentatively designated 1998SF 36 by the discoverer, who agreed to dubbing their asteroid “Itokawa” in August, 2003. Itokawa was name after the late Dr. Hideo Itokawa, the father of Japanese rocket development. His first 13cm-long rocket, Pencil, was successfully fired fifty years ago. The asteroid, 500m x 300m in size, is circling around the sun at a distance of approximately 300milion kilometers from the earth.

Image of Itokawa, taken just before Hayabusa’s arrival

Courtesy: JAXA:ISAS

MV-5 rocket soared up and up as planned. Ten minutes and 10 seconds after launching, the rocket separated and put MUSES-C into the trajectory around Earth. 14 minutes after launching, the spacecraft deployed its solar panels, capturing the sun further 16 minutes later. At 1:52p.m.on the same day, Deep Space Network in California received the signal from MUSES-C followed by DSN in Canberra at 3:00 p.m. These events assured the successful launching of the mission. According to JAXA’s naming tradition, the mission team announced the new name, “Hayabusa,” in association of an image of a falcon which flies toward a prey precisely, hovers over it and then zips down to capture it in an instant.

Hayabusa, is about 510kg in wet mass and is three-axis stabilized with 1.6m x 1.1m x 1.0m dimension. In order to explore a far-away minor planet with an unknown shape, the spacecraft is provided with highly autonomous function to control itself by means of optical sensing as well as data processing. Hayabusa dealt with the first critical phase to get over, firing of the first of the four ion engines, in three weeks after its rift-off. It survived the second one, an Earth swing-by scheduled for May 19, 2004. Hayabusa swept past an altitude of 3700km over the East Pacific Ocean. This event slingshot the spacecraft into the trajectory toward Itokawa with additional navigational velocity.

One of the key technologies of Hayabusa spacecraft is the on-board ion-engine thrusters used for round-trip trajectory propulsion between Earth and Itokawa. They survived the pre-launching operation lasting for more than 10,000 hours in the laboratory and functioned perfectly in interplanetary space for 25,800 hours until August 28, 2005.Then trajectory maneuver of the spacecraft switched to the bipropellant thrusters for final approach to the asteroid at 10kilometers per hour

Hayabusa will hover around Iokawa for about a month to make an overall investigation. The asteroid explorer will start detailed observation in mid-October to prepare for sample collection. In November, two soft-ball sized target markers and Minerva, the tiny robot, will be released toward the asteroid. Sample collection will be conducted twice for acquiring about two grams of samples. Minerva will investigate the asteroid’s surface. Early in December, Hayabusa will leave away from Itokawa’s orbit to get back to Earth. In June of 2007, Hayabusa will release the re-entry sample capsule into Earth’s atmosphere. The capsule will deploy its parachutes and soft-land in the desert area in Southern Australia.

Minerva, the robot(left) and target marker(right below)