2020/08/07
The University of Tokyo
Keio University
A research group—comprising Professor Hirofumi Saito (at the time of research, now Professor Emeritus) of the Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA); Professor Shinichi Nakasuka of the Department of Aeronautics and Astronautics, Graduate School of Engineering, The University of Tokyo; and Professor Seiko Shirasaka of the Graduate School of System Design and Management, Keio University—has developed an ultra-high-speed data transmission communication system from small satellites in low Earth orbit. This was part of the Cabinet Office's Impulsing Paradigm Change through Disruptive Technologies Program (ImPACT) (Project title: "Small Synthetic Aperture Radar Satellite System for On-Demand and Immediate Observation," 2015–2018). The group then conducted an on-orbit demonstration experiment using JAXA's Rapid Innovative Satellite Technology Demonstration-1 (RAPIS-1), which was launched in January 2019.
After receiving the ultra-high-speed X-band (8 GHz band) data transmission signal from the RAPIS-1 satellite with a 10-meter antenna owned by the Institute of Space and Astronautical Science at the Usuda Deep Space Center, JAXA Tracking and Communication Center, the signal was temporarily recorded on a data recorder and then demodulated and decoded using software. As a result, the experiment successfully demonstrated communication speeds of 2.65 and 3.3 gigabits per second, the world's fastest direct data transmission using radio from a low Earth orbit satellite.
This communication system effectively utilizes X-band (8 GHz) radio waves, which allow for low-cost systems unaffected by weather, by employing polarization multiplexing and advanced modulation techniques such as 64APSK (64-ary Amplitude and Phase Shift Keying) and 256APSK (256-ary Amplitude and Phase Shift Keying). This achieves world-class frequency utilization efficiency (8.4 bit/s/Hz and 10.8 bit/s/Hz).
In future space applications, missions that acquire optical and radar images of the Earth's surface "anytime, anywhere" using constellations of small Earth observation satellites are expected to bring about significant transformations in society and economic activities. This on-orbit demonstration is expected to make a major contribution to the technology for transmitting large volumes of data from these Earth observation and monitoring missions to the ground at a low cost.
For the full press release, please see below.