Selection of Site for Hayabusa2 Landing on Asteroid in Final Stage

January 6, 2019

Tokyo--The Japan Aerospace Exploration Agency, or JAXA, is carefully examining locations on asteroid Ryugu for its Hayabusa2 spacecraft's landing as early as late this month, after giving up the probe's first touchdown attempt that had been scheduled for late October 2018.

In September-October last year, JAXA conducted a total of three rehearsals for the landing on candidate areas around the equator of Ryugu.

During the rehearsals, JAXA succeeded in lowering Hayabusa2 to a point 12 meters above Ryugu's surface by a method of autonomously controlling the craft's altitudes and attitudes using a laser sensor.

"We've got to the point where the only thing left for us to do is make a landing, so we're fully prepared in terms of technique," said Yuichi Tsuda, Hayabusa2 project manager at JAXA.

The problem is that Ryugu's surface is rockier than expected. This made JAXA to give up the first landing attempt.

Hayabusa2 has a set of solar panels with a width of some 6 meters, and a one-meter-long cylindrical device to collect samples of Ryugu will be landed on the asteroid when the craft touches down.

For a safe touchdown, it is necessary that there will be no rocks with a height of over 50 to 70 centimeters around the landing site.

Currently, the space agency expects an error range of up to 15 meters between the targeted landing site and the location where Hayabusa2 would actually touch down. "At the moment, we can't guarantee a perfect landing," Tsuda said.

A JAXA team aims to reduce the error gap to 10 meters or less by improving Hayabusa2's autonomous control program based on its movements during the rehearsals.

It is looking for relatively less rockier areas each with a diameter of 20 meters. The team is working to find the safest location by estimating the heights of nearly 100 rocks based on the lengths of their shadows.

"I've had a dream in which I stand at the landing place," Tsuda said. "After accurately understanding the conditions of the asteroid's surface, we'll aim to land Hayabusa2 safely and perfectly." Jiji Press