[meteorite-list] Hayabusa Spots Its Asteroid Target

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Aug 18 11:36:28 2005
Message-ID: <200508181516.j7IFG9I02737_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn7863-samplereturn-craft-spots-its-asteroid-target-.html

Sample-return craft spots its asteroid target
Kelly Young
New Scientist
17 August 2005

Japan's Hayabusa spacecraft has spotted its quarry - a 630-metre-long
asteroid named Itokawa. In September 2005, Hayabusa will try to
rendezvous with the asteroid and, eventually, touch its surface.

If it succeeds, Hayabusa will be the first ever mission to bring back
samples from an asteroid. Scientists could then compare the raw asteroid
material to meteorites on Earth to find a good match. Once Itokawa's
composition and spectra is known, it could help determine the chemical
make-up of other asteroids just by comparing their spectral
characteristics, recorded by Earth-based observatories.

Unlike NASA's high-profile Deep Impact probe, which crashed into Comet
Tempel-1 on 4 July 2005, Hayabusa has not attracted a lot of public
attention. "This is a stealth mission," says NASA's Don Yeomans, the US
project scientist for the mission. "Nobody knows it's there."

Hayabusa's cameras first sighted Itokawa on 29 July. Currently, the
spacecraft is less than 35,000 kilometres from the asteroid. The
pictures it has been gathering will help guide the spacecraft to its quarry.
          
White-knuckle time

When it closes in - in September - it will slow to match the velocity of
the asteroid, effectively "parking" about 20 kilometres away, to map the
asteroid's surface. At the end of the month, the probe will come to
within 7 km of Itokawa and create a more detailed map.

Then comes the tricky part of the mission. The spacecraft will approach
Itokawa until a fabric cone touches the surface for a moment, triggering
the firing of a tantalum pellet into the asteroid at 300 metres per second.

The probe will then try to collect 100 milligrams of material thrown up
by the pellet impact. It will repeat this cycle up to two more times
with further pellets. "That's probably the most risky part - the white
knuckle time is when the spacecraft comes down for these sampling
activities during the second half of November," Yeomans told New Scientist.

During its initial descent, the spacecraft will also deploy a little
hopper called Minerva. For one or two days, the coffee-can-sized device
will attempt to make several 10-metre-high hops around the asteroid's
surface, taking temperature readings and snapping pictures.

Hayabusa will return to Earth in June 2007 for a landing in the
Australian outback. Scientists will harvest the samples and whisk them
away to curation facilities in Japan and Houston, Texas, US.

Giant solar flare

Ultimately, the mission is a test of new technologies. Hayabusa is
equipped with an ion drive engine and an autonomous navigation system.
The sample collection system and the re-entry capsule are also a new
test. NASA's Genesis spacecraft attempted to retrieve samples of the
solar wind and return them safely to Earth, but crashed into the Utah
desert in September 2004. Some of its samples were saved, however.

The Hayabusa probe launched from Kagoshima in Japan on 9 May 2003. A
giant solar flare in 2003 degraded its solar panels, meaning less energy
for its ion propulsion system. It was supposed to arrive at Itokawa in
mid-2005, but its slow-down means a September arrival is scheduled.

Yeomans says this did not affect the mission at all. If it had arrived
earlier, Hayabusa would have had to stand by and wait because the
asteroid was behind the Sun, relative to Earth.

One of the spacecraft's three reaction wheels, which control
orientation, stopped working on 31 July, but mission operators say they
can continue the mission with just two functioning wheels.
Received on Thu 18 Aug 2005 11:16:09 AM PDT