Dr Stefania Soldini is an Associate Professor in Space Engineering, an internationally recognised expert in flight dynamics and planetary science applied to asteroid research and Director of the new Zero-G AstroLab facility.
In July, she had the opportunity to return twice to the Japan Aerospace Exploration Agency (JAXA) in Sagamihara, Japan, where she previously worked on the Hayabusa2 mission.
My first visit coincided with Hayabusa2’s historic close flyby of asteroid Torifune on 5 July, while my second visit later in the month was to participate in the post-flyby scientific discussions with the mission team. Returning to JAXA, where I spent several years working on Hayabusa2, was both professionally rewarding and personally nostalgic.
I have been involved with the Hayabusa2 mission since 2016, when I moved to JAXA’s Institute of Space and Astronautical Science (ISAS). I first joined through a JSPS Postdoctoral Fellowship and later became an Aerospace Project Research Associate (APRA) within the flight dynamics team responsible for operating Hayabusa2 around asteroid Ryugu.
Dr Stefania Soldini with her former supervisors, Prof. Takanao Saiki, Principal Investigator of the Small Carry-on Impactor (SCI) operations, and Prof. Yuichi Tsuda, former Hayabusa2 Mission Project manager
These years shaped much of my research career and continue to inspire my work in spacecraft guidance, navigation and control for small-body missions.
Hayabusa2 was designed as a rendezvous mission, allowing the spacecraft to operate alongside asteroid Ryugu for more than a year. During its nominal mission, it successfully collected both surface and subsurface samples through two touchdowns in 2019, following the creation of the first-ever artificial crater on an asteroid.
After departing Ryugu in November 2019, Hayabusa2 returned its sample capsule to Earth in December 2020, bringing back 5.4 grams of asteroid material. While this marked the successful completion of the nominal mission, it also marked the beginning of a new phase of exploration as the spacecraft continued its extended mission towards asteroid Torifune and renamed Hayabusa2# (SHARP – Small Hazardous Asteroid Recounnaissance Probe).
Unlike its operations at Ryugu, Hayabusa2 was never designed to perform a high-speed flyby. With fixed cameras and limited ability to rapidly reorient the spacecraft, capturing close-up images while travelling at nearly 5 km/s required extremely precise trajectory design and navigation. The spacecraft successfully passed within approximately 800 metres of the centre of the 450-metre-wide asteroid, demonstrating the high-precision autonomous guidance and trajectory control that will be essential for future planetary defence and deep-space exploration missions.
A close-up image of asteroid Torifune, revealing its distinctive contact binary shape (Image Credit JAXA).
The most exciting part for me was following the close flyby from JAXA with many of the colleagues I had worked alongside during the Ryugu operations. The ten-minute wait for the signal confirming that Hayabusa2 had safely passed Torifune was both exciting and nerve-racking, bringing back vivid memories of our arrival at Ryugu several years ago.
Less than two hours after the flyby, the first close-up images of Torifune were downlinked to Earth. Seeing the asteroid’s true shape for the first time and comparing it with what we had previously inferred from ground-based radar observations made every minute of the wait worthwhile. Every time we visit a new asteroid, it feels like discovering a new world.
The Hayabusa2 operations team at JAXA following the successful completion of solar conjunction operations around asteroid Ryugu in December 2018
The Hayabusa2 operations team at JAXA following the successful completion of solar conjunction operations around asteroid Ryugu in December 2018. Dr Stefania Soldini is pictured with colleagues after leading the design, planning and execution of the spacecraft trajectory manoeuvres during this critical phase of the mission.
Hayabusa2 has been a truly inspiring mission, and seven years later it continues to shape my research. It has influenced the design of our new Zero-G AstroLab facility and the research carried out by members of my team, helping to inspire the next generation of engineers.
My current research at the University of Liverpool focuses on autonomous spacecraft guidance, navigation and control for planetary defence missions, and Hayabusa2 continues to demonstrate the technologies that will enable future autonomous close-proximity operations around small bodies. Reconnecting with former colleagues, discussing the latest scientific data, and witnessing another milestone in the mission reminded me how long-term international collaborations continue to advance both science and engineering.
Hayabusa2 Joint Science Team Members