Guinness World Records™ Recognizes “DAICHI-4”’s Data Transmission as the World’s Fastest

On July 23, 2024, we announced the successful high-speed data transmission of 3.6 Gbps with the Ka-band direct transmission system of the Advanced Land Observing Satellite-4 “DAICHI4” (ALOS-4), and this record was recognized by the Guinness World Records™ (*1) on December 19, 2024.

On December 19, 2024, an official certificate presentation ceremony was held at the Tsukuba Space Center. In the presence of JAXA staff, the official certificate was awarded to Yukihiro Kankaku, Project Manager, ALOS-4 Project Team, Space Technology Directorate I, and Masanobu Yajima, Director, Research Unit I, Research and Development Directorate, from the Guinness World Records official adjudicator.

Contents of GUINNESS WORLD RECORDS™ Certificate

The fastest RF direct downlink speed from an Earth observation satellite to ground stations is 3.6 Gbps and was achieved by JAXA and Mitsubishi Electric Corporation (both Japan) with the Satellite ALOS-4 on 23rd July 2024.

This represents the successful high-speed data transmission of observation data from the Advanced Land Observing Satellite-4 “DAICHI-4” (ALOS-4) to the ground stations at a rate of 3.6 Gbps, which was recognized by the Guinness World Records.

When you hear the phrase “high-speed data transmission of 3.6 Gbps from the satellite to the ground station”, you may not understand how fast it really is. The term “bps” refers to the rate at which 1 bit of data is transmitted per second. Since 1 byte is equal to 8 bits, a rate of 3.6 Gbps means that 450 MB (Mega Byte) of data can be transmitted per second, or 27 GB (Giga Byte) per minute.
If you compare this to a smartphone that we use daily, it is incredible that it would go through a 50 GB plan in less than 2 minutes.

Words of joy for GUINNESS WORLD RECORDS™ achievement

These are the comments from Project Manager Kankaku and Director Yajima, who had been involved in the development of “DAICHI-4” from the concept design phase and received the certificate at the official certificate presentation ceremony.

“From the concept design phase of “DAICHI-4”, we aimed to expand the observation swath by four times while maintaining the resolution of the previous satellite “DAICHI-2”. Consequently, we identified the challenge of transmitting the larger amount of observation data to the ground as a key issue. We held numerous discussions with members of the Research and Development Directorate at an early stage and decided to apply new technology for higher speed data transmission. Since then, we have worked with the members of the Research and Development Directorate for design and testing in the development phase. I am very pleased to have achieved this goal with the support of the members and our partner, Mitsubishi Electric Corporation. I am sure that we will face many challenges when examining the next satellite, but we will do our best together.

Yukihiro Kankaku, Project Manager, ALOS-4 Project Team, Space Technology Directorate I

Instead of the proven X-band, we decided to use Ka-band, which has a wider bandwidth, during the concept design phase of “DAICHI-4”, and I am happy that we have achieved our goal of 3.6 Gbps transmission. Additionally, it’s also excellent that the technology to compensate for signal distortion (*2), which had been successful in the research of our Directorate, has been adopted and made possible. While this time the transmission rate was 3.6 Gbps, we will continue our research and development towards an even higher rate of data transmission.

Masanobu Yajima, Director, Research Unit I, Research and Development Directorate

Clearer Images with Fourfold Increase in Observation Swath and Dual-Polarization Observation!

What new capabilities have become with the increase in data transmission rate of “DAICHI-4”?

“DAICHI-4” is constantly circling the Earth in an orbit called a synchronous sub-recurrent orbit.
(CG movie of satellites orbiting the Earth, including “DAICHI-4” can be viewed at “Satellites Watching Over the Earth“.)
Satellite observation data has to be sent to the ground before we can use it, but communication with the ground is only possible for about ten minutes when the satellite is flying close to the space above the antennas, known as ground stations. Therefore, once “DAICHI-4” observation data is recorded in on-board semiconductor memory, it is sent to the ground station when it can be transmitted.

However, if data transmission is slow, a lot of data cannot be sent in 10 minutes.
“DAICHI-2” has a transmission rate of 0.8 Gbps, allowing it to transmit 60 GB of data in 10 minutes. However, at the same speed, the observation distance that can be transmitted decreases even if the observation swath increased.
As a result, “DAICHI-4” was designed to have a transmission rate 3.6 Gbps, 4.5 times faster than that of “DAICHI-2”, and is capable of transmitting 270 GB of data in 10 minutes.

Therefore, “DAICHI-2” can observe a swath of 50 km with 3 m resolution, while “DAICHI-4” can observe four times that swath, 200 km with 3 m resolution. Additionally, it enables constant dual-polarization observation with HH polarization (horizontal polarization transmission and horizontal polarization reception) and HV polarization (horizontal polarization transmission and vertical polarization reception).

The data acquired from the dual-polarization observations can be synthesized to generate a false-color image, making it easier to identify the ground surface conditions. This is expected to contribute to understanding disaster situations, monitoring deforestation, etc.

DAICHI-2	⇒	DAICHI-4
0.8 Gbps	Transmission Rate 4.5 times faster	3.6 Gbps
60 GB	Data that can be transmitted in 10 minutes	270 GB
50 km	Observation Swath 4 times larger	200 km
Dual-polarization observation is possible, but not constant.	Observation Method	Dual-polarization observation with 3 m resolution constantly is possible in the region around Japan.

Ever-increasing expectation for high-speed data communications

Ground stations at the Tsukuba Space Center (Ibaraki), the Earth Observation Center (Saitama), the Esrange Space Center, Swedish Space Corporation (SSC) (Sweden), and the Inuvik Satellite Station Facility(Canada) are used for “DAICHI-4”. The Tsukuba Space Center and the Earth Observation center receive the same data 3-4 times a day. The Esrange and Inuvik ground stations are located at high latitudes, allowing them to receive data once every 100 minutes as “DAICHI-4” orbits the Earth.
Although observation data is sequentially sent to the ground stations, we have to deal with huge volumes of data. For this reason, efforts are being made to reduce the data volume, for example by lowering the resolution to 10 m, depending on the area to be observed.

Further applications of higher-speed data transmission are expected in the future and R&D in this area is being promoted in the Research and Development Directorate. The future development is exciting.

Related information

• Advanced Land Observing Satellite-4 “DAICHI-4” (ALOS-4)
• Success in high-speed data transmission of 3.6G bps with the Ka-band direct transmission system of the Advanced Land Observing Satellite-4 “DAICHI4” (ALOS-4) (Japanese Only)

*1: Guinness World Records is a registered trademark of Guinness World Records Limited. *2: Research and Development Directorate website “Research into high-speed transmission systems” (Japanese Only)
https://www.kenkai.jaxa.jp/research/society5/kaband.html