Japan Aerospace Exploration Agency (JAXA)

Since the Halley’s Comet exploration project in 1985, the Japan Aerospace Exploration Agency has adopted Fujitsu’s orbit determination technology in all domestic solar system exploration projects that have been undertaken in Japan. Although determining a probe’s orbit in deep space beyond the Earth is extremely difficult, the orbit determination group of the Institute of Space and Astronautical Science is working alongside Fujitsu in orbit determinations in ongoing missions to ensure their success.

The story so far

Fujitsu supports in the challenging field of orbit determination

Dr. Yoshikawa explained the difficulty of determining a solar system probe’s orbit. “A large factor contributing to the difficulty is the great distance. Compared to a satellite near the Earth, the distance between a solar system probe and the Earth is far greater, which causes changes in speed to be small when measured with radio waves. This is why estimation is difficult. In addition, a longer distance results in weaker radio waves and more noise. Poorer data quality results in less precise orbit determination.” Other factors contributing to difficulty in orbit determination include tiny forces, such as solar radiation pressure, and fluctuations of the output of thrusters and ion engines that serve as the propulsion system of a probe.

Fujitsu is an active player in the field of orbit determination. It has been responsible for the development and operation of orbit determination systems in all of Japan’s solar system exploration projects for more than 30 years – from the 1985 Halley’s Comet exploration project (Sakigake and Suisei deep-space probes) to present. Dr. Yoshikawa adds, “Fujitsu has been helping us with orbit determination in deep space past the Moon in particular. In Japan, it is only Fujitsu and us that conduct orbit determination in deep space.”

Responsible for determining solar system probes’ orbits as a project team member

The orbit determination systems that Fujitsu provides calculate the locations of probes precisely based on data of probes that ground stations have tracked with radio waves and in some cases data of target celestial objects that those probes have observed. However, delivering systems is not the only job. Dr. Yoshikawa explains Fujitsu’s role, “Since deep space exploration involves many new challenges, the software created initially is often not applicable without modification. When calculations that an orbit determination system performs are a bit off, we have a discussion with Fujitsu to modify the method. And Fujitsu and we make improvements by enhancing the system and modifying operations. Fujitsu has been participating in projects while fulfilling its responsibility as a member of the orbit determination team, not a distant, external partner company.”

Difficult situations are commonplace in orbit determination for a solar system probe. Dr. Yoshikawa recalls, “When a problem occurred in the Nozomi Mars exploration project, Fujitsu’s technology saved us. Fujitsu adopted the method of processing the weak radio waves that are too poor in quality to use under normal circumstances and extracting data usable for orbit determination in order to operate the probe. That was a very difficult job but nevertheless Fujitsu accomplished it.”

Hayabusa2 was launched in 2014 to explore the Ryugu asteroid.

It is the successor to the first Hayabusa asteroid probe, which was launched in 2003. Fujitsu is involved as a key member of the Hayabusa2 orbit determination team.

［Published in 2019］