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JAXA (Japan Aerospace Exploration Agency) has announced the Hayabusa 2 probe will attempt to land on the asteroid Ryugu in early 2019 to collect surface samples, after unexpected discoveries about the surface necessitated a postponement.
Speaking at the Foreign Correspondents’ Club of Japan on December 12, Hayabusa 2 Project Manager Yuichi Tsuda of JAXA’s Institute of Space and Astronautical Science (ISAS) and ISAS Director Hitoshi Kuninaka related the groundbreaking achievements made by the mission so far, and the tasks which still lay ahead.
The spacecraft was launched from Japan in 2014 with the mission of traveling to the asteroid Ryugu, deploying rovers onto its surface, and then descending to the surface itself to collect the largest samples ever taken from an asteroid. It arrived at its destination in June 2018.
According to JAXA, this mission has four goals. In addition to gathering more scientific information and exploring previously uncharted bodies in space, the information collected by Hayabusa 2 will also help improve planetary defense: “We are gaining the technology to identify hazardous asteroids prior to actual impact,” Project Manager Tsuda explained, “Universities and the U.N. are seriously studying this.” Finally, the mission is also looking into planetary resources, as asteroids such as Ryugu may potentially hold large quantities of water or useful minerals.
Hayabusa 2 carries rovers that can collect data and take photographs from the surface. Three of them have been deployed already: MINERVA II-1a and MINERVA II-1b, were released together on Ryugu’s northern hemisphere, while the third, MASCOT, was deployed in the south. The rovers are designed to hop and roll in Ryugu’s low gravity (one eighty-thousandth that of earth’s), allowing them to move about the surface, taking photos and measurements from several different locations. A fourth rover is scheduled to be deployed later in 2019. according to JAXA.
Mr. Tsuda reported that the initial observations produced a number of surprises. First, Ryugu’s shape was unexpected. Seen from earth, the asteroid was indistinct, but photos taken as Hayabusa 2 approached revealed it to be shaped like a top, with a wide circular bulge around the equator and narrower at the poles. In addition, JAXA’s findings showed Ryugu to be almost perfectly upright with respect to its orbit, and to be significantly darker than expected.
One discovery that caused “a lot of headaches” according to Mr. Tsuda, however, was the condition of the surface. Images taken from high overhead by Hayabusa 2, and confirmed by photos from the rovers, revealed that Ryugu is covered in craters and strewn with boulders, some as large as 130 meters across. This makes landing the probe a risky undertaking. “The problem is, because Ryugu is bumpy, the original accuracy of 50 meters is not enough for a safe landing. We were now obliged to narrow down the landing accuracy to as small as 20 meters diameter,” said Mr. Tsuda.
After deciding to postpone the landing to 2019, the team began making practice descents. “For these five months,” said Mr. Tsuda, “we conducted 7 descents. 4 were low altitude, less than 100 meters. Based on these results we concluded that a latitude range of +/- 30 degrees has proven to be accessible with higher than expected guidance accuracy. In October, we decided to do additional rehearsals to precisely evaluate our landing accuracy.” These rehearsals gave the team the confidence to reschedule the landing and sample collection for early 2019.
Once it completes its observations, Hayabusa 2 will leave Ryugu for the year-long return trip to earth.
JAXA Official Website: http://global.jaxa.jp