After a journey of 42 months and 2 billion miles (3.2 billion km), Japan Aerospace Exploration Agency’s Hayabusa-2 spacecraft finally reached its intended target, a small asteroid named Ryugu, on June 27, 2018. This remarkable achievement was confirmed when the spacecraft closed to just 12 miles (20 km) from the surface of the diamond-shaped asteroid.
This illustration depicts JAXA’s Hayabusa-2 spacecraft at the asteroid Ryugu. Image credit: German Aerospace Center / CC-BY 3.0.
Ryugu, also known as 1999 JU3, is a near-Earth Cg-type asteroid. Its name refers to Ryūgū (Dragon Palace), a magical underwater palace in a Japanese folktale.
This object was discovered in May 1999 by astronomers with the Lincoln Near-Earth Asteroid Research.
It measures approximately 0.56 miles (900 m) in diameter and orbits the Sun at a distance of 0.96-1.41 astronomical units (AU) once every 474 days.
The asteroid and Hayabusa-2 are currently around 174 million miles (280 million km) from Earth.
“Together with all of you, we have become the first eyewitnesses to see asteroid Ryugu,” said Dr. Yuichi Tsuda, project manager from the Japan Aerospace Exploration Agency.
“I feel this amazing honor as we proceed with the mission operations.”
Launched at the end of 2014, Hayabusa-2 is supposed to observe Ryugu and bring surface material samples back to Earth in 2020.
The 600-kg spacecraft has multiple payloads: Optical Navigation Cameras ONC-T/W1/W2, Near Infrared Spectrometer, Thermal Infrared Imager, Laser Altimeter, Sampling System, three small rovers MINERVA-II-1A/1B/2, reentry capsule and lander MASCOT.
The MASCOT (Mobile Asteroid Surface Scout), a lander built by the German Aerospace Center in collaboration with the French space agency CNES, is scheduled to land on the asteroid in early October 2018.
“In a world first, MASCOT will travel across the surface in a hopping motion, allowing it to conduct measurements at multiple locations,” the project scientists said.
“We are hoping to get a better insight into the properties and structure of near-Earth asteroids in order to understand these very old remnants of the formation of the Solar System. This will offer insights into the formation of the planets and enable more effective planning of possible asteroid defense missions.”
This image of the asteroid Ryugu was captured by the Optical Navigation Camera – Telescopic (ONC-T) on JAXA’s Hayabusa-2 spacecraft on June 26, 2018, from a distance of 13.7 miles (22 km). Image credit: JAXA / University of Tokyo / Kochi University / Rikkyo University / Nagoya University / Chiba Institute of Technology / Meiji University / Aizu University / AIST.
The latest images from Hayabusa-2’s ONC-T camera show that Ryugu has a very unusual shape.
“From a distance, Ryugu initially appeared round, then gradually turned into a square before becoming a beautiful shape similar to fluorite,” Dr. Tsuda said.
“Now, craters are visible, rocks are visible and the geographical features are seen to vary from place to place. This form of Ryugu is scientifically surprising and also poses a few engineering challenges.”
“First of all, the rotation axis of the asteroid is perpendicular to the orbit. This fact increases the degrees of freedom for landing and the rover decent operations. On the other hand, there is a peak in the vicinity of the equator and a number of large craters, which makes the selection of the landing points both interesting and difficult.”
“As far as we are concerned, Ryugu is an ideal test object for us, as it is only 900 m in diameter and there are many members of the same asteroid class in near Earth orbits,” said Dr. Ralf Jaumann, of the Institute of Planetary Research at the German Aerospace Center.
“Its unusual, angular shape, revealed in the latest images, is exciting.”
“The scientifically surprising shape of Ryugu and its many craters will make the selection of a suitable landing site for MASCOT both fascinating and challenging,” said MASCOT project leader Dr. Tra-Mi Ho, from the Institute of Space Systems at the German Aerospace Center.
“MASCOT will provide completely new insights into the material that made up the Solar Nebula, which has been resting on the surface of the asteroid for around 4.5 billion years.”
