[meteorite-list] Hayabusa on Track for Landing in Two Weeks

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 31 May 2010 12:26:21 -0700 (PDT)
Message-ID: <201005311926.o4VJQLbS014575_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/news/n1005/30hayabusa/

Hayabusa on track for landing in two weeks
BY STEPHEN CLARK
SPACEFLIGHT NOW
May 30, 2010

Two weeks before its scheduled return to Earth, Japan's Hayabusa
asteroid explorer is halfway through a series of unprecedented ion
engine burns to aim the probe for a narrow re-entry corridor toward
Australia.

The Japanese space agency says the spacecraft remains on track for its
landing June 13 at the Woomera Test Facility in South Australia. The
re-entry should occur around 1400 GMT, or in the late night hours of
June 13, Australian time.

The Hayabusa mothership will release the 16-inch-wide entry capsule
about three hours before landing as the probe travels around 25,000
miles from Earth. During re-entry, temperatures around the capsule will
reach about 4,900 degrees Fahrenheit, but the tiny craft will be
protected by a carbon-fiber heat shield.

Parachutes will deploy to slow the capsule's speed for touchdown in the
Australian outback.

Because Hayabusa's chemical fuel tanks are empty, Japanese engineers had
to devise ways to keep the spacecraft on course using ion thrusters,
highly-efficient engines typically used for long-duration burns lasting
thousands of hours.

Hayabusa's sole operational ion thruster, afflicted by its own technical
trouble, has fired three times since early April to guide the spacecraft
toward Earth. Each trajectory correction maneuver, which would normally
be executed using chemical engines, takes up to several days to complete
because of the ion engine's low thrust.

The craft completed its third correction firing early Thursday, Japanese
time. The nearly 100-hour burn changed Hayabusa's velocity by 11 mph and
put the probe on course for the Earth rim point, an imaginary target 200
kilometers above the planet's surface.

The fine-tuning burns beginning in April came after the ion thruster
completed its long-term propulsion phase in late March.

The probe is currently traveling 3.5 million miles from Earth, according
to the Japan Aerospace Exploration Agency.

Hayabusa will fire its ion engine two more times in the coming weeks to
target the spacecraft's trajectory for the Woomera landing site.

The next burn is scheduled to begin around June 6 to bend Hayabusa's
trajectory from the Earth rim point to its destination in Australia. A
final maneuver, tentatively timelined for three days before re-entry,
will correct any errors in the course toward the landing site.

Hayabusa, which is about the size of a compact car, launched from Japan
in 2003 and spent three months exploring asteroid Itokawa in late 2005.
Hayabusa means falcon in Japanese.

Although the craft likely did not achieve its objective of collecting
samples from Itokawa, scientists are hopeful Hayabusa's landing capsule
carries some asteroid residue. Even if the container is empty, the $200
million mission would still complete the first round-trip voyage to and
from an asteroid, assuming the crippled spacecraft can complete the
final two weeks of its journey.
Received on Mon 31 May 2010 03:26:21 PM PDT