On July 11, 2019, the Asteroid Explorer "Hayabusa2" succeeded in touching down for the second time on the asteroid Ryugu. During its first touchdown in February of this year, the explorer took samples of substances from the surface of the asteroid. Four months later, "Hayabusa2" blasted a pure copper mass to create an artificial crater on the asteroid, which was followed by this second touchdown mission. Unlike the first touchdown, this mission has a high likelihood of having been able to acquire samples of substances that came from underneath the asteroid's surface.

Yuya Mimasu, who was the person responsible for controlling the positioning of "Hayabusa2," reflected back on the difficulties that they had, especially because it was their second touchdown.

"The sensor at the bottom of the explorer became dirty during the first touchdown from the dust and sand that had risen up. Because of this, we needed to change the settings on the camera that captures our target marker (for the touchdown point)."

They searched for the best settings, and held repeated discussions with various persons involved.

"We proposed a certain setting after having conducted repeated simulations, but we were informed that this setting paid too much attention to ensuring safety, thereby increasing the probability of causing an abort (with the explorer aborting the descent by its autonomous decision). And so, we changed it to a timing that was at the razor's edge of what we could allow. This gave me a renewed awareness of the fact that, when faced with a challenging mission, the key to success is in finding the right balance between safety and the achievability of the mission."

Mimasu says that at the moment of success, "I was thrilled, and at the same time, there was a feeling of relief from having done what we set out to do, and a sense of not being able to believe that we actually succeeded, and other various emotions all jumbled together."

"We shook hands with the members and shared the joy. What made a particularly strong impression upon me was when I shook hands with my superior, with whom I had worked closely together from the time of development, and said to each other, 'we really achieved everything that we set out to do.' I felt proud to be a member of this team, that built up a succession of achievements in various missions over the past year since the explorer arrived at Ryugu."

Mimasu says, "At the beginning, we were not perfect, both as a team and as individuals."

"We worked together by filling in where the other was lacking, which in a way is a fundamental way of doing things, and everyone worked with a high mindset. And I believe this is what enabled us to get to where we are now. 'You must create a good team in order to be able to achieve major results.' This is the lesson that I myself learned through this experience."

The point of the second touchdown was named Uchide-no-kozuchi, after a Japanese folktale of a magical hammer of the same name that produces treasures when it is used, with the hope that the samples acquired from this spot would lead to many discoveries. "Hayabusa2" is scheduled to return to Earth at the end of 2020. The samples brought back by this explorer may be able to provide us with hints toward unravelling the mysteries of the universe.