Japan Aerospace Exploration Agency (JAXA), and NEC Corporation (NEC), the prime contractor of the laser-communication terminals for the Laser Utilizing Communication System (LUCAS)*1, performed the world's fastest optical communication (wavelength band: 1.5 μm, communication speed: 1.8 Gbps) using LUCAS between the Advanced Land Observing Satellite-4 “DAICHI-4” (ALOS-4)*2 and the Optical Data Relay Satellite in geostationary orbit at a distance of about 40,000 km, and successfully completed the first transmission of observation data to a ground station through the geostationary satellite.

Observation image of “DAICHI-4” transmitted by LUCAS

In October 2024, JAXA and NEC successfully achieved the optical inter-satellite communication*3 between “DAICHI-4” equipped with the Optical Leo Laser Communication Terminal (OLLCT) dedicated to an Earth observation satellite and the Optical Data Relay Satellite equipped with the Optical Geo Laser Communication Terminal (OGLCT) dedicated to a geostationary satellite, and we have continued technical demonstrations. As a result, we successfully transmitted “DAICHI-4” observation data using optical communication. 

The success of this data transmission utilizing LUCAS enables immediate downlinking of a large amount of observation data which is difficult to achieve through direct communication to ground stations in areas lacking accessible ground stations. The first image downlinked through LUCAS, generated from a large amount of mission data observed by "DAICHI-4" over approximately 30 minutes, traversing the Arctic, Europe, and the African continent. While direct transmission to ground stations requires multiple transmissions, the use of LUCAS narrowed the acquisition of observation data of vast areas to a single transmission.

OGLCT:Laser-communication terminal aboard the GEO (Geostationary) satellite b(Optical inter-satellite communication instrument for GEO satellite)

JAXA and NEC have been engaging in optical communication in space since the 1990s. Optical communication in space is also identified as a technology of strategic importance in the Space Technology Strategy formulated by the Japanese government for fiscal year 2023. JAXA has advanced research and development in optical communication as a solution to the increasing capacity and immediacy requirements of data transmission for future Earth observation satellites. NEC has been responsible for designing the LUCAS system, manufacturing laser communication terminals, supporting satellite system tests, and managing the initial functional verification operations of satellite systems. Building on this success, we will continue to contribute to the advancement of Japan's space development by accelerating the technological development of optical inter-satellite communication in collaboration with related organizations and partners.

Click here to know more about JAXA's Optical Inter-Satellite Communication System "LUCAS"