JAXA and NEC: Success in high-speed optical communication between satellites!
・OLLCT and OGLCT realize large-volume data transmission to ground stations
・1.5μm communication optical wavelength, communication speed of 1.8Gbps is the fastest in the world
Summary from an article published in ImpressWatch.
Optical inter-satellite communication system: (LUCAS)
1. Japan’s radar satellite “Daichi-4” (ALOS-4) is equipped with LUCAS.
2. Success in optical communication data transmission with NEC’s relay satellite (40,000 km away).
NEC’s optical data relay satellite:
The optical data relay satellite developed by NEC is a satellite in geostationary orbit.
From 2020, NEC has developed an optical data relay satellite (OGLCT) and is attempting to connect with LUCAS (OLLCT).
JAXA’s advanced radar satellite: “Daichi-4”
In July 2024, JAXA launched “Daichi-4”.
1. “Daichi-4” is equipped with an optical terminal for Earth observation satellites (OLLCT).
2. The optical data relay satellite is equipped with an optical terminal for geostationary satellites (OGLCT).
This optical communication was successful between the optical terminal (OLLCT) and the optical terminal (OGLCT).
Disadvantages of the conventional method:
Limits on direct data communication with the ground:
1. Observation satellites are constantly orbiting the Earth, so there are limitations on direct data communication with the ground.
2. Direct data transmission is only possible during the time when the satellite passes over the receiving facility.
Advantages of the optical communication method:
Optical relay satellites allow constant communication:
1. Optical data relay satellites are deployed as geostationary satellites in the sky above Japan.
2. Therefore, optical data relay satellites can transmit data to the ground at any time.
Note that data transmission from optical data relay satellites to the ground is carried out by radio waves.
Features of NEC’s optical communication method:
Highly secrecy and prevention of communication interception and jamming:
1. Highly directional compared to radio waves, with less interference with other communication systems.
2. Difficult to intercept or jam, high secrecy.
Radio wave communication allows interception within a 60km diameter range, but with optical beams this is reduced to within 560m.
Precise positioning of satellites:
The exact positions of satellites need to be known to establish communication.
1. The Optical Inter-Satellite Communication System (LUCAS) developed by NEC identifies the positions of satellites.
2. Fast and accurate communication is achieved by various methods of acquisition and tracking.
Test results of DAICHI-4:
On January 10, DAICHI-4 took 30 minutes of images with 10m resolution and 200km width.
While taking images, it succeeded in sequentially transmitting data to an optical data relay satellite.
A large amount of data of 13,000km, which is about 1/3 of the circumference of the Earth, was instantly transmitted.
Image data released:
1. Seawater in the Arctic Ocean:
2. Budapest, the capital of Hungary:
3. Nature reserve in Nigeria:
You can confirm that the images were taken with a high resolution of 10m resolution.
Future LUCAS development: Optical data relay satellite
Optical communications with the International Space Station “Kibo”, development of an optical ground station, and data relay experiments with aircraft will be carried out.