On January 25, 2024, a photograph of Japan's first successful pinpoint lunar landing by the Smart Lander for Investigating Moon (SLIM), was released. The historic photo was captured by the Transformable Lunar Robot LEV-2 (nicknamed "SORA-Q"), jointly developed by Sony Group Corporation and Japan Aerospace Exploration Agency (JAXA), TOMY Company, Ltd. (TOMY), and Doshisha University. We spoke with Masaharu Nagata (Exploratory Deployment Group, Technology Platform, Sony Group Corporation), who led the Sony team, about what became the world's first fully autonomous robot lunar exploration project, and Sony's technologies that made it possible.

World's first fully autonomous robot
that captured SLIM landing on the moon

LEV-2, jointly developed by the four parties, is the world's smallest and lightest fully autonomous lunar exploration robot at approx. 80mm in diameter (before transformation) and weighing around 250g. TOMY's knowledge and ideas from toy development have been put to use in the endearing spherical form and the frame design which allows it to travel across the lunar surface in a motion inspired by sea turtles.

LEV-2 was launched into space on board the SLIM lander and was released onto the lunar surface together with LEV-1, an ultra-compact Lunar Excursion Vehicle, on January 20, 2024. It then autonomously found the SLIM, taking pictures as it moved along, and transmitted high-quality image data of the lunar lander and its surroundings to the LEV-1, thereby delivering photos of the lunar surface to earth.

IoT board computer "SPRESENSE" and Sony's technology combine
to make a super compact and lightweight robot

The development of the lunar exploration robot began in 2016 by JAXA's Space Exploration Innovation Hub and TOMY. Sony joined in 2019, and Doshisha University followed in 2021. Sony's engineers were assigned the mission to realize a fully autonomous robot from the concept created by JAXA and TOMY for "a sphere-shaped robot that transforms to move around on uneven terrain." In addition, Sony led the selection of components as well as the technological development for the robot's motion control and imaging.

During the early stage of development, the team singled out a low-power IoT board computer "SPRESENSE™" developed and commercialized by Sony Semiconductor Solutions, which they determined to be the most suitable technology for what would be the world's smallest and lightest lunar exploration robot. Despite SPRESENSE's small size and low power consumption, it boasts a high performance programmable to work with camera and sensing devices enabling the robot to drive autonomously, capture images and perform other operations. After repeated environmental tests to verify its resistance to radiation and external shocks, SPRESENSE was selected as the core processor to control all the robot's movements. The development environment and source code are open to the public, which was also an advantage in working together with partners.

However, minimizing the system load would be necessary to allow all tasks, including autonomous mobility, image capturing, and wireless communication, to be operated by SPRESENSE. To this end, engineers who had honed their skills in device design and development worked steadily on configuring the circuits and boards.

A further challenge was image processing, which is a vital element in enabling the robot to travel to the proper position as well as capture images. It was not possible to perfectly replicate the space environment and the conditions of the lunar landing for the tests on earth. "Without knowing the correct answer, we considered how to reliably detect and photograph the SLIM, and finally devised a system by which the LEV-2 could recognize the SLIM from the gold color of its exterior insulation. We then repeatedly experimented with every conceivable situation, including various light and shadow contrasts and reflections, to improve the accuracy of the technology. "

Expertise in manufacturing
enabling a new approach in space exploration

Nagata is also involved in Sony's "Earth MIMAMORI Platform" project, which aims to contribute to the sustainability of the Earth and society through Sony's technologies, and has been working on new communication technologies that leverage outer space. Through such experience, he is aware how challenging outer space development is, where you face risks and harsh environment that are completely different from those on earth, including impact of launch, temperature changes and cosmic rays.
"Every single component needs to be specialized for space, which requires a great deal of time and effort to develop. With that in mind, I feel that the development of the robot by these four parties proceeded quite quickly," he says.

In fact, an automated robot prototype was completed within about a year after Sony's participation in 2019. This allowed ample time for field testing and environmental testing by JAXA. This speedy development was made possible by a new approach taken by TOMY and Sony, both with roots in manufacturing, though in different fields.

"LEV-2 utilizes consumer devices for its components, and its frame is simple enough to be assembled by hand. Moreover, both companies excel at mass production of consistent and high-quality products. We were able to efficiently improve the overall quality of LEV-2 during its development by building multiple prototypes equipped with the same technology and testing them in parallel to verify the technologies each party was responsible for."

This was a novel approach from a new perspective, where in conventional development experiments were repeated with the single actual vehicle to be launched into space.

Recently, more companies are showing an interest in space and entering the field by developing new technologies such as satellites or launching new businesses. Looking back on the joint research, Nagata says, "We were able to prove with our own hands that the technologies and skills we have honed at Sony can contribute to space, which is very gratifying. I also realized firsthand that fundamental principles of manufacturing remains the same, whether on the ground or in space. I would like to continue exploring the potential of Sony's technologies and development expertise in new fields such as outer space."