QSOL(Quantum-Small Optical Link)

Structure of QSOL

QSOL (Quantum-Small Optical Link) 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 National Institute of Information and Communications Technology (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.1

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.2 This transmission used the free-space optical Ethernet communications error-correction technology developed by Sony CSL.3

Conceptual diagram of the experiment

1 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)

2 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).