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Speeding through the solar system tasked with a world’s first mission

HAYABUSA, the asteroid explorer, was tasked with 5 missions including bringing back samples from asteroid “Itokawa”, to seek answers to the mysteries behind the birth of the solar system. It also had an important role in demonstrating 4 critical technologies to be deployed in ambitious future sample return probe which were ion engine, autonomous navigation system, sampling and sample return.
HAYABUSA was launched on May 9, 2003 with the M-V launch vehicle. Its return to Earth on June 13, 2010 set remarkable world records.


HAYABUSA at a glance
Challenges involved in obtaining an asteroid surface sample

On May 9th, 2003, a probe was launched from Uchinoura, which is in Kagoshima prefecture, on a mission to reach an asteroid far from Earth. This probe, called HAYABUSA, was developed to investigate planets by collecting samples and bringing them back to Earth for analysis. There are clues to understanding the origin of our solar system in asteroids. By analyzing a sample from such an asteroid, we hope to obtain important clues for unraveling the mysteries of our solar system.

The asteroid Itokawa targeted by HAYABUSA was about 300 million kilometers from Earth when HAYABUSA reached it, and has a diameter of only 540 meters. Although HAYABUSA is an unmanned probe, it faces the exceedingly difficult mission of landing on a tiny asteroid, obtaining a surface sample, and then returning to Earth. Cutting-edge technology enables HAYABUSA to achieve its mission and has been a subject of interest for space professionals. This includes the new type of engine and autonomous navigation that were used for the HAYABUSA design.

HAYABUSA has succeeded at many missions, and, after overcoming a variety of unexpected obstacles, is on its way home.

The five missions of HAYABUSA

HAYABUSA is responsible for five major missions.

1.Using new ion engine technology to fly between planets

A newly developed electric propulsion engine (an ion engine) that is more fuel efficient than conventional chemical propulsion engines is being used to propel HAYABUSA between planets. Running three ion engines simultaneously for as long as 40,000 hours represents one of HAYABUSA's major successes, the first success of its kind.

2.Autonomous navigation

By using devices such as a laser altimeter and short range sensors, HAYABUSA has been able to determine its own position, approach its targets, and use autonomous navigation to change its attitude. In addition to approaching Itokawa and flying in the same orbit as the asteroid (referred to as a rendezvous), HAYABUSA also touched down on Itokawa by analyzing information on its own.

3.Obtaining an asteroid sample

Because the asteroid Itokawa has extremely weak gravity, HAYABUSA could not land on the asteroid's surface, so a method for enabling HAYABUSA to obtain a surface sample in an instant was devised. The method was to use a piece of equipment projecting from the bottom of HAYABUSA called a sampling horn, which was approximately one meter long and 20 centimeters in diameter, to shoot a metal pellet into the asteroid surface, so the rocks and dust that flew up as a result could be obtained. Trying to use this method was a major challenge for HAYABUSA.

4.Earth swing-by

Swing-by refers to a technique for using the gravity of a celestial body to change the orbit or speed of a spacecraft or probe. To face Itokawa, as HAYABUSA used its ion engines to correct its direction, it also used Earth's gravitational pull to accelerate, performing an Earth swing-by. HAYABUSA is the first spacecraft to use a combination of ion engine acceleration and an Earth swing-by.

5.Re-entry capsule

HAYABUSA is returning its capsule for obtaining a sample from Itokawa to Earth. This represents the first time an attempt has been made to return a sample from the surface of an asteroid further away than the Moon to Earth. The capsule will be released immediately before HAYABUSA re-enters Earth's atmosphere and will then fall to Earth.

Overcoming various obstacles to return to Earth

November 2005 Chemical engine fuel leak

In November 2005, HAYABUSA touched down on the asteroid Itokawa for the second time, but there was a fuel leak from a chemical engine after take-off. Because the leaked fuel changed to a gas and blew out of the probe, HAYABUSA lost its attitude, and its location was unknown for seven weeks.

After restoring communication with the probe, xenon gas used by the ion engines to propel the probe was directly shot out, because the chemical engine originally used to control the attitude could no longer be used. This was not an original intention for the gas, but using the gas in this way made it possible to gradually adjust the attitude, and, by March 2006, HAYABUSA was miraculously recovered.

The efforts by the control room team to save HAYABUSA took an entire year, and, in April 2007, operations to bring the probe home were finally started.

November 2009 Ion engine failure

In November 2009, with HAYABUSA close to Earth, one of its ion engines failed. HAYABUSA's journey was unexpectedly long, and the engine's life had finally expired. However, even in the face of this difficult situation, the operation team did not give up, and they combined features of the working engines (of which there were originally four) into one engine, using which they achieved cross control to resume operation. HAYABUSA has overcome many difficulties, and although literally covered in wounds at this point, is expected to reach Earth in June 2010.