JAXA and NEC realize world's first 1.5-μm-band inter-satellite optical communication for ultrahigh-capacity mission data transmission

On January 23, the Japan Aerospace Exploration Agency (JAXA) and NEC Corporation, the prime manufacturers of optical communication equipment for the "LUCAS" optical inter-satellite communication system, announced that they successfully conducted the world's fastest optical communications (1.5-μm band, communication speed of 1.8 Gbps). They performed communications between the advanced radar satellite "DAICHI-4 (ALOS-4)" and an optical data relay satellite in a geostationary orbit approximately 40,000 km away using LUCAS for the first time, transmitting observation data to a ground station via a geostationary satellite.

In October last year, JAXA and NEC established optical inter-satellite communications between the DAICHI-4 satellite equipped with the LUCAS Optical Leo Laser Communication Terminal (OLLCT) and "optical data relay satellite" equipped with the Optical Geo Laser Communication Terminal (OGLCT). They have continued technical demonstrations. Consequently, observation data from DAICHI-4 were successfully transmitted after establishing optical communication. Successful data transmission using LUCAS enables to instantly downlink large amounts of observation data in areas where there are no available ground stations, which was difficult to perform by transmitting data via direct communication with ground stations.

While direct data transmission to ground stations requires multiple transmissions, the use of LUCAS enables to acquire observation data over a very large area with a single transmission. Light has a considerably wider bandwidth than radio waves (5 THz at a wavelength of 1.5 μm); therefore, it can transmit much more information. Additionally, because a very narrow beam is used, there is no concern regarding interference or interception. Thus, the use of light is indispensable for realizing high-speed, large-capacity communications in space in the future.

With this optical data relay system, LUCAS can transmit large amounts of data at a rate 7.5 times faster than the previous-generation radio wave-based data relay satellite "Kodama" (DRTS), which has a transmission rate of 240 Mbps.