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Japanese Researchers Examine Asteroid Skin

Posted: August 26th, 2011 | Author: | Filed under: Applied Science, Astronomy, Cosmology, Michael Courtenay, Physics, Science, Technoid, Tecnoid | Tags: , , , , , , | Comments Off on Japanese Researchers Examine Asteroid Skin

Asteroid dust collected by a Japanese spacecraft – HAYABUSA – has given scientists their first look into the outer covering of an asteroid.

The asteroid explorer HAYABUSA – previously named Muses-C – was launched in 2003 by JAXA – Japanese Aerospace Agency – The craft succesfully rendezvoused with Asteroid 25143-Itokawa, located some 320 million km from Earth in 2005. Hayabusa successfully re-entered Earth’s atmosphere in June 2010. As Hayabusa burnt up she dropped her payload- a heat resistant capsule –  safely at Woomera in outback South Australia.

“Until now, asteroid exploration had been a one-way trip; however, the Hayabusa is a round-trip space mission. We’re now designing an improved next-generation space ship and are expecting the arrival of the Grand Navigation Era to the Solar System, such as a round trip to a main belt asteroid or to Venus, or a round trip via a deep space port” said project manager Junichiro Kawaguchi

Professor Trevor Ireland form the Australian National University says the dust has now been analysed and matches dust from asteroids that have hit Earth.

“We see the rocks of meteorites, we don’t see the skin because when the meteorites come in they hit the upper atmosphere and it all burns off,” he explained.

“So the big thing about this mission is that we’ve actually got the skin of an asteroid for the first time.”

The spacecraft took its dust particles from the surface of asteroid 25143 Itokawa.

The analysis showed ordinary chondrites, the most common meteorites found on Earth, are from S-type asteroids. It indicates that Itokawa is an asteroid made of reassembled parts of a once-bigger asteroid.

Hayabusa was been developed specifically to investigate asteroids, indeed one asteroid in particular. The craft explored “Asteroid 25143-Itokawa” named after the late Dr. Hideo Itokawa, the father of Japan’s space development program.

Until now, the only extra-terrestrial celestial body from which we have gathered samples is the Moon. But since the matter that comprises large bodies such as the planets and the Moon has changed over time due to thermal processes, these bodies cannot provide us with a pristine record of the solar system. Asteroids, on the other hand, are believed to be small enough to have preserved the state of the early solar system and are sometimes referred to as celestial fossils. A soil sample from an asteroid can give us clues about the raw materials that made up planets and asteroids in their formative years, and about the state of the inside of a solar nebula around the time of the birth of the planets.

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From her launch on 9 May 2003 at 04:29:25 UTC on an M-V rocket from the Uchinoura Space CenterHayabusas xenon ion engines – four separate units – operated near-continuously for two years, slowly moving Hayabusa toward her September 2005 rendezvous with Asteroid 25143-Itokawa. As Hayabusa arrived, the spacecraft did not go into orbit around the asteroid, but remained in a station-keeping heliocentric orbit close by.

Another innovation aboard HAYABUSA was her Autonomous Navigation System, which enabled the probe to approach a far-away asteroid without human guidance. The system works by measuring the distance to the asteroid with the Optical Navigation Camera, and using Light Detection and Ranging.

Hayabusa surveyed the asteroid surface from a distance of about 20 km, the “gate position”. After this the spacecraft moved closer to the surface (the “home position”), and then approached the asteroid for a series of soft landings and for the collection of samples at a safe site. Autonomous optical navigation was employed extensively during this period because the long communication delay prohibits Earth-based real-time commanding. At the second Hayabusa touchdown with its deployable collection horn, the spacecraft was programmed to fire tiny projectiles at the surface and then collect the resulting spray. Some tiny specks were collected by the spacecraft for analysis back on Earth.

Hayabusa carried a tiny mini-lander  – weighing only 591 g, and approximately 10 cm tall by 12 cm in diameter – named “MINERVA” (short for MIcro/Nano Experimental Robot Vehicle for Asteroid). Unfortunately, an error during deployment resulted in the craft’s failure.

This solar-powered vehicle was designed to take advantage of Itokawa’s very low gravity by using an internal flywheel assembly to hop across the surface of the asteroid, relaying images from its cameras to Hayabusa whenever the two spacecraft were in sight of one another.

MINERVA was deployed on 12 November 2005. The lander release command was sent from Earth, but before the command could arrive, Hayabusa‘s altimeter measured its distance from Itokawa to be 44 m and thus started an automatic altitude keeping sequence. As a result, when the MINERVA release command arrived, MINERVA was released while the probe was ascending and at a higher altitude than intended, so that it escaped Itokawa’s gravitational pull and tumbled into space.

Had it been successful, MINERVA would have been the first space hopper to see action. Instead it joins ranks with the hopper carried on the failed Phobos 2 mission, which also never saw use.

“Hayabusa not only gathered samples but also observed the asteroid with various scientific devices and measures. For that purpose, it was equipped with Telescopic Wide-View Cameras, Light Detection and Ranging, as well as with a Near Infrared Spectrometer. Hayabusa also emploedy a hopping robot, which moved around on the asteroid’s surface.” said Junichiro Kawaguchi

Scientists’ current understanding of asteroids depends greatly on meteorite samples, but it is very difficult to match up meteorite samples with the exact asteroids from which they came. Hayabusa would solve this problem by bringing back pristine samples from a specific, well-characterized asteroid. Accordingly, Hayabusa “will bridge the gap between ground observation data of asteroids and laboratory analysis of meteorite and cosmic dust collections,” says mission scientist Hajime Yano. In comparing the data from the onboard instruments of the Hayabusa with the data from the NEAR Shoemaker mission will put the knowledge on a wider level.

The Hayabusa mission has a very deep engineering importance for JAXA. It allows JAXA to further test its technologies in the fields of ion engines, autonomous and optical navigation, deep space communication, and close movement on objects with low gravity among others. Second, since it was the first-ever preplanned soft contact with the surface of an asteroid (the NEAR Shoemaker landing on 433 Eros was not preplanned) it has enormous influence on further asteroid missions.



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