Sony Computer Science Laboratories, Inc. (Sony CSL, President and CEO: Hiroaki Kitano) has successfully downlinked video data via gigabit Ethernet from the Quantum Small Optical Link (QSOL) installed aboard the Japanese Experiment Module "Kibo" on the International Space Station (ISS) to the optical ground station for satellite communications (hereinafter, optical ground station)¹ of the National Institute of Information and Communications Technology (NICT). The transmission was made using Sony CSL's free-space optical Ethernet communications error-correction technology, an independently developed standard.² This marks the first use in the world of this standard to make a transmission.

QSOL is the optical antenna component of the compact Secure Laser Communications Terminal for Low Earth Orbit (SeCRETS). It was commissioned by the Ministry of Internal Affairs and Communications to demonstrate the technology in orbit and was jointly developed by NICT, Next generation Space system Technology Research Association (NeSTRA), The University of Tokyo, SKY Perfect JSAT Corporation, and Sony CSL. SeCRETS was launched on August 2, 2023, to the ISS and installed to the IVA-replaceable Small Exposed Experiment Platform (i-SEEP) on the outside of "Kibo". Subsequently, experiments of 10 GHz clock optical transmission between the ISS in low Earth orbit and a portable optical ground station were successfully conducted to share private keys and to demonstrate information-theoretically secure transmission of one-time pad encryption.³

Conceptual diagram of the experiment

QSOL is composed of an optical transmission signal processing unit for demonstrating 1.25 Gbps high-speed transfer and contains a gimbal for acquisition and tracking of the optical ground station, an optical bench with fine pointing system, and a control system.

Structure of QSOL

For this experiment, QSOL's compact periscope gimbal system tracked and acquired an uplink from NICT's portable optical ground station and then downlinked to their 1.5 m optical ground station. An optical link was established, demonstrating the use of QSOL in orbit. Additionally, video data was downlinked from QSOL in orbit and received by NICT's 1.5 m optical ground station. This transmission used the free-space optical Ethernet communications error-correction technology developed by Sony CSL.

In 2020, Sony CSL transmitted high-definition (HD) image data via Ethernet, marking the first time in the world that a successful link was established using laser communication devices designed for small satellites. Later, in 2021, Sony CSL achieved the first successful downlink at a commercial optical ground station.

This time, a video data file was successfully transmitted. Through this, Sony CSL has thoroughly demonstrated robust data transmission between space and ground, a compact gimbal system with large field of view, and the tracking and acquisition of a small aperture optical antenna (portable optical ground station) to establish an optical link. Sony CSL considers this result a significant step toward realizing commercial transmission between space and ground, and foresees great potential in its social implementation in the future.

¹ NICT Optical Ground Station
A telescope facility built to aid the development of technology related to space communications. The station has a total of four telescopes with apertures of 1.5 m and 1.0 m in Koganei, Tokyo; 1.0 m in Kashima, Ibaraki; and 1.0 m in Onna, Kunigami-gun, Okinawa. The experiment this time used the telescope with a 1.5 m aperture.

² 142.10-O-1 Reed-Solomon Product Code for Optical Communication, an experimental
specification (orange book) of the Consultative Committee for Space Data Systems (CCSDS).

³ Successful private key sharing and high confidentiality communications between the International Space Station and the ground ~ Expectations for practical satellite quantum cryptography communications ~ 
https://www.sonycsl.co.jp/press/prs20240418/
（18 Apr 2024, press release, Japanese only）

This research and development was carried out as part of the "Research and Development of Quantum Cryptography in Satellite Communications (JPJ007462)" within the "Research and Development Project for Priority ICT Technologies (JPMI00316)" of the Ministry of Internal Affairs and Communications.
Reference: Ministry of Internal Affairs and Communications press release
Dated 14 June 2018.
Results of the call for proposals for research and development of information and communication technologies in 2018.
http://www.soumu.go.jp/menu_news/s-news/01tsushin03_02000247.html