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Here is the mission of the Japanese spacecraft Hayabusa2: Fly to a carbon-rich asteroid between the orbits of Earth and Mars, study it for a year and a half and then bring back some pieces for further study on Earth.
Like most space missions, it's much easier said than done. Launched in 2014, Hayabusa2 is barely approaching its target, Ryugu, an asteroid about half a mile wide. Japanese astronomers who study it say that it has the shape of a peak or even a pearl of abacus.
This is a big improvement over the beginning of June, when it returned a photo taken at a distance of about 1,600 miles – the asteroid then had only three pixels in diameter and looked like something in the style of Minecraft.
Why did it take so long to get there?
Hayabusa2 is powered by ionic motors, which accelerate xenon-charged atoms with an electric field to generate thrust.
Ionic engines are a very effective form of propulsion but not very powerful. This means that Hayabusa2 can carry a lot less fuel than traditional thrusters, but it also means that it can not take a fast and direct route. The spacecraft used a flyby of the Earth in December 2015 to accelerate and match its trajectory with the inclined orbit of the asteroid.
Hayabusa is the Japanese word for the peregrine falcon.
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When will the spacecraft reach Ryugu?
Starting Monday, the spacecraft is about 15 miles away, and is expected to arrive around Wednesday around 12.5 miles from the space rock. It currently crawls up to Ryugu at a relative speed of about 4 inches per second.
Why are they studying this asteroid?
Asteroids are pieces remnants of the disk of gas and dust that formed around the young sun and never quite coalesced in a planet. They contain almost immaculate compounds that help to tell what the primitive solar system looked like 4.5 billion years ago.
Ryugu, as dark as coal, is a type C asteroid, or carbon, meaning that it is full of carbon molecules known as organic compounds, possibly including amino acids, the building blocks proteins. These molecules are not always associated with biology and can form from chemical reactions in deep space, but asteroids could have seeded the Earth with organic matter that has led to life.
About three quarters of the asteroids in the solar system fall into type C. And Ryugu's rotation time was a surprise to the scientists who study it.
"Until now, we know of several vertex-shaped asteroids, but all have a short spin period around 3 hours," said Makoto Yoshikawa, head of the Hayabusa mission2. "The spin period of Ryugu is about 7.5 hours, so this question is quite interesting from a scientific point of view."
This space rock was discovered in 1999 and did not receive a name until 2015. Ryugu owes its name to the Ryugu-jo, or Dragon Palace, a magical underwater palace in a Japanese folk tale.
What will he do once he's there?
If the spacecraft is able to meet its schedule, Hayabusa2 will descend at the end of July to within 3.1 miles of Ryugu's surface to measure the gravitational field around the asteroid. In September or October, Hayabusa2 should perform its first "touch operation" on the asteroid.
At this point, he can deploy one or more of the five small rovers that he carries. It can also deploy a lander of European construction then.
Then, it will take a break in November and December, because the sun will be directly between Ryugu and Earth, blocking communications.
After that, the spacecraft will make some extra landings, as well as drop a copper projectile into the asteroid to create a crater. This will allow the spacecraft to collect material below the surface. (The projectile is made of copper because this metal is easily distinguishable from what the asteroid is made of.)
By the end of 2019, Hayabusa2 must leave the asteroid and return to Earth. As he flies in 2020, he will drop a capsule with the asteroid samples.
Does not NASA do something like that too?
Yes. The Osiris-Rex spacecraft is currently moving towards another carbon-rich asteroid known as Bennu, and it will also collect samples and bring them back to Earth. Bennu is even smaller than Ryugu, about 500 meters wide. Osiris-Rex will begin its approach to Bennu in August and begin to observe the remote asteroid in October.; he will not come back with his samples until 2023.
NASA and Japanese scientists plan to exchange samples of both asteroids to compare similarities and differences.
Has Japan ever done that?
As the 2 indicates in Hayabusa2, it is the second time that JAXA, the Japanese space agency, is sending a spaceship on an asteroid.
Hayabusa2 is an improved version of Hayabusa, who visited a stony asteroid, Itokawa, in 2005. Despite several technical problems at Itokawa, Hayabusa returned a capsule to the Earth in 2010 containing 1500 particles of the asteroid.
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