Japan Aerospace Exploration Agency (JAXA)
Using orbit determination technology to support unravel the mysteries of the solar system, earth, and the origins of life
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.
We have started R&D on the Martian Moons eXploration (MMX) program seeking to launch spacecraft in the first half of the 2020s. This is a more challenging project than Hayabusa2, so more accurate orbit determination will be important. We will continue improving the technique of orbit determination.
Dr. Makoto Yoshikawa
Associate Professor, Department of Spacecraft Engineering, Institute of Space and Astronautical Science
Japan Aerospace Exploration Agency
JAXA’s Institute of Space and Astronautical Science: continues to venture into new frontiers
Japan Aerospace Exploration Agency (JAXA) was established in 2003 as a result of the integration of the Institute of Space and Astronautical Science (ISAS), the National Aerospace Laboratory of Japan (NAL) and the National Space Development Agency of Japan (NASDA). Projects that they conduct cover a vast spectrum of fields, including the use of space environments, contributions with satellites and probes, space science research, solar system exploration research, and astronautical technology research.
“The Hayabusa2 asteroid probe is observing an asteroid called Ryugu in order to clarify the origin and evolution of the solar system and raw-material substances of life forms. The probe has successfully touched down on the surface of Ryugu in February 2019,” explains Dr. Makoto Yoshikawa, Associate Professor at ISAS, JAXA, and Mission Manager of Hayabusa2 project. In 2018, he was selected for ‘Nature’s 10’ as one of ten people worldwide who have had a significant impact on the scientific community chosen by the science journal Nature.
Dr. Yoshikawa conducts research at ISAS to determine the orbits of artificial satellites and probes. He explains, “Orbit determination is to estimate where a satellite or a probe is and what its speed is at a specific time. The location and speed of a satellite or a probe are calculated through radio-wave communication with an antenna on the Earth. The orbit determination group estimates the current location of a probe and the orbit design group figures out the best way to move that probe based on the estimation results.”
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.
Outcome and next step
Evolving through experience for higher precision in orbit determination accuracy
Dr. Yoshikawa emphasizes that experience is crucial in orbit determination. “Although Japan has launched many satellites, the number of probes that went to or past the Moon is only around 10. Various predictions made on the Earth often turn out completely incorrect in space. When encountering trouble or an unexpected situation, we have to analyze it in preparation for similar circumstances. Experience is of vital importance for growth.” Drawing on their vast experience, the orbit determination group and Fujitsu continue to improve the accuracy of orbit determination.
As of the end of 2018, ISAS is operating the Akatsuki, IKAROS, Hayabusa2, and MIO solar system probes. The orbit determination group and Fujitsu will continue to determine the orbits of these probes in operation now.
Dr. Yoshikawa expressed a vision of the future, saying, “In addition, research and development on the Martian Moons eXploration (MMX) project has been commenced for launching a probe in the first half of the 2020s. This project is even more difficult than Hayabusa2 and more precise orbit determination is crucial.” Going forward, Fujitsu will support Japan’s projects for solar system exploration with its orbit determination technologies.
Japan Aerospace Exploration Agency (JAXA)
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［Published in 2019］