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Mission extended: The next decade of Hayabusa2’s adventures

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The asteroid 1998 KY26 compared in size to Ryugu

After delivering its precious cargo of samples from the asteroid Ryugu to Earth on December 6, 2020(JST), Hayabusa2 will set out on a new asteroid exploration mission. But it isn’t scheduled to arrive at its next destination until 2031. That eleven-year odyssey will test the limits of Hayabusa2’s capabilities.
The mission extension will prolong Hayabusa2’s journey through space to fully seventeen years from launch. That testifies to the reliability of the spacecraft as designed and built by NEC. The hardy spacecraft’s further travels will provide valuable experience to build on in the future when exploring Jupiter and other worlds beyond. Never before has a Japanese space explorer braved the unforgiving environment of outer space for so long. Even if the extension of the mission takes a serious toll on the engines, the cameras, and the other scientific instruments on board, that in itself constitutes otherwise unattainable data, so it will still be considered a plus.
In 2026, Hayabusa2 is scheduled to observe the asteroid 2001 CC21 with its cameras and other equipment while flying by at high speed. That asteroid is believed to consist of a rare type of rock never studied by a probe before. It may be made of the same stuff as meteorites, which contain material left over from the early days of the solar system. Demonstrating a connection would be a historic discovery on the part of Hayabusa2.
Hayabusa2’s ultimate destination is the mysterious asteroid 1998 KY26, which has a diameter of approximately 30 meters — far smaller than Ryugu’s. It rotates on its axis about every 11 minutes, so its days and nights are just five minutes long. Hayabusa2 plans to rendezvous with this tiny, fast-spinning object. If it succeeds, it will be an unprecedented feat.

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The asteroid 1998 KY26 compared in size to Hayabusa2
The asteroid measures approx. 30 m in diameter, about the size of a basketball court

Rendezvousing with the asteroid as it rapidly orbits the sun will take some fancy footwork. The explorer will, while keeping the asteroid in its sights, need to stop at a fixed height above the surface and then remain there. Imagine how difficult it would be to fly through the air while matching your trajectory with that of an object traveling at high speed on the ground. Delicate maneuvering would be required so you didn’t get ahead of your target or lose sight of it. That’s the trick that Hayabusa2 will have to pull off — only above a little-understood asteroid that’s spinning rapidly and constantly shows a different face.
Despite its modest dimensions, 1998 KY26 is actually a threat to Earth. Celestial objects of similar size have struck our planet innumerable times in the past in the form of meteorites. There’s a risk of a direct hit once every century or two. If Hayabusa2 can observe the asteroid up close, it should be possible to determine the density and hardness of the rock and what minerals it consists of. And if the asteroid ever gets too close to Earth, knowing what it’s made of will enable scientists to draw up plans for diverting its course. Such data, then, is invaluable for planetary defense.
With half its ion engine propellant still remaining, Hayabusa2 is ready to embark on a new journey. Its extended mission will be as great a challenge as its six-year odyssey to date. After all, it has a lot left to achieve: observing an asteroid still shrouded in mystery, rendezvousing with another that spins super-fast, and contributing to our planet’s defenses.

Written by Ayano Akiyama
Published: December 4, 2020

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