Asteroid Probe's Return to Earth Keeps Scientists on Edge
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Earth return of Japan's Hayabusa asteroid probe and release of its sample capsule. CREDIT: C. Waste and T. Thompson (NASA/JPL-Caltech) |
BRECKENRIDGE,
Colo. ? A "welcome home" team of eager scientists is anxiously
awaiting this month's return of a Japanese asteroid probe and its planned
nosedive into Australia because ? just maybe ? it is toting a tiny, but
prized, piece of space rock.
If all goes
well, the sample return capsule of Japan's Hayabusa spacecraft will parachute down on June 13 over
a sparsely populated land within Woomera Test Range
in South Australia.
Blazing
through the sky, the capsule?s re-entry would be both a triumph of stick-to-it-ness and a tribute to scientific curiosity.
That?s the
view of Peter Jenniskens, the principal investigator
of the NASA-sponsored Hayabusa Re-Entry Airborne
Observing Campaign from the SETI Institute in Mountain View, Calif.
Jenniskens detailed the
nail-biting role of airborne sky watchers at Meteoroids 2010 ? an international
conference on minor bodies in the solar system held here May 24-28.
The meeting was sponsored in part by NorthWest Research Associates/CoRADivision,
NASA, Los Alamos National Laboratory and the Office of Naval Research.
First, a
little history
The Japan
Aerospace Exploration Agency (JAXA) launched Hayabusa
on May 9, 2003. The probe was lofted to try out new engineering technologies
including a shakeout of ion propulsion, as well as autonomous navigation,
sampler and re-entry capsule concepts.
In late
2005, Hayabusa loitered around and surveyed asteroid
25143 Itokawa for some three months, relaying
impressive imagery and science data about the celestial rock of ages. Two
surface sample runs were carried out, but whether or not the asteroid
collecting equipment worked as planned is not clear. However, a specimen of
dust and pebbles from Itokawa may have been snared.
After Hayabusa departed the S-class asteroid,
it had to overcome numerous engineering difficulties en route back to Earth,
such as ion engine woes, broken reaction wheels, a leaking thruster, even a
lengthy loss of communication with ground controllers.
?Fortunately,
they were terrific in tackling these issues,? Jenniskens
told SPACE.com. ?They found a solution every time and that?s really very
impressive. It is a really big achievement when the object actually comes into
the atmosphere and is brought back to Earth?an incredible achievement.?
Importing
asteroid bits
Jenniskens said Hayabusa?s troubles spurred worry at times that the
re-entry would have to be scrapped.
But now the
spacecraft is being maneuvered for its re-entry into Australia. A critical
trajectory correction maneuver of the spacecraft is set for June 4, followed
five days later with a fine-tuning tweak that refines the return capsule?s
landing spot.
Also in order
is the legal paperwork for the foreign-made hardware to touch down in
Australia. Hayabusa is truly an import, not only from
Japan but from outer space too. Japan obtained import consent via the
Authorized Return of Overseas Launch Space Object from the Space Licensing and
Safety Office of the Australian Government.
Hayabusa will be the third
re-entry event directly from interplanetary transfer orbit to the Earth,
following in the wake trail of NASA?s Genesis
and Stardust entries, said Masa-yuki Yamamoto of
Kochi University of Technology in Japan.
At the
meeting, Yamamoto detailed the ground observation equipment being set up to
record Hayabusa?s fiery plunge.
Three
optical stations are being installed near the Woomera
Prohibited Area in Australia to profile the capsule?s ablating thermal
protection system. Additionally, infrasound and seismic sensors will be
installed on four stations to detect atmospheric shock waves emitted from the
incoming capsule, Yamamoto said.
The return
capsule is outfitted with a parachute that provides high reflectivity for radar
signals and a radio responder to locate it within desert brush. After recovery,
the sample return capsule will be taken to Tokyo, opened there to assess if it
indeed holds treasured bits of asteroid Itokawa.
Winging
it
The Hayabusa Re-Entry Multi-instrument Aircraft Campaign makes
use of NASA?s DC-8 Airborne Laboratory. On the spacecraft?s re-entry day, the
instrument-packed aircraft will be flying at 39,000 feet in a race-track
pattern at some distance from the landing site.
An
international lineup of scientists will be onboard, Jenniskens
noted, at the ready to flip the switches on an array of equipment, from high
definition TV cameras, intensified cameras, high frame-rate cameras,
near-infrared sensitive cameras and spectrographs. Mounted to numbers of
aircraft windows, this gear will attempt to snare the light from the capsule
during its speedy and heated entry.
Jenniskens is no stranger to
eyeing human-made meteors. He ran a similar airborne campaign for the Stardust
sample return capsule entry in January of 2006 and took part in observing the
September 2004 Genesis spacecraft re-entry.
He was also
a principal investigator for the joint European Space Agency/NASA
multi-instrument aircraft campaign that monitored the controlled
destructive re-entry over the South Pacific of Europe?s 13-ton Automated
Transfer Vehicle, the Jules Verne, in September 2008.
?Every one
of these so far has had its unique challenges,? Jenniskens
said. ?For Hayabusa we?re basically getting two
experiments at the same time,? he said, pointing out that the spacecraft bus
itself will reenter and bust up into pieces right behind the sample return
capsule.
It is not
clear how well the 16-inch (40-cm) diameter capsule will stand out from the
debris of the main spacecraft, Jenniskens said.
Spike of
adrenaline
The Hayabusa return capsule is unlike the shape of the Stardust
capsule. It also makes use of a different heat shield material to thwart torrid
temperatures similar to those seen by a craft zooming in from Mars and akin to
the speed of natural meteors.
The 40-pound
(18-kg) capsule?s entry, ejection of its heat shield, parachute system
deployment and landing will occur in the middle of the night in dark-sky
conditions.
As for the
airborne observing campaign, ?to do all the coordination takes a while,? Jenniskens stated. ?This has been in the works for a
year-and-a-half.?
Hayabusa will hot-foot its
way toward terra firma at well over 26,000 mph (12 kilometers per second). As
it plows into Earth?s atmosphere and turns into an artificial fireball, that
event will last all of a minute.
?It?s very
brief. Just leading up to the event is a spike of adrenaline,? Jenniskens said. ?There are second thoughts and worries.
When you push the button on your instrument, will it really do what you set out
to do? Is the lens cap off??
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Leonard
David has been reporting on the space industry for more than five decades. He
is past editor-in-chief of the National Space Society's Ad Astra and Space
World magazines and has written for SPACE.com since 1999.









