The National Institute of Information and Communications Technology (NICT) has successfully demonstrated 2 Tbit/s Free-Space Optical (FSO) communication using small optical communication terminals that can be mounted on satellites and HAPS, marking a world first for this technology.

This experiment involved horizontal free-space optical communication between two types of small portable optical terminals developed by NICT: a high-performance FX (Full Transceiver) installed at NICT Headquarters (Koganei, Tokyo) and a simplified ST (Simple Transponder) installed at an experimental site 7.4 km away (Chofu, Tokyo). Despite the difficult conditions of an urban environment with atmospheric turbulence that disrupts laser beams, the system maintained a stable total communication speed of 2 Tbit/s via Wavelength Division Multiplexing (WDM) transmission of 5 channels (400 Gbit/s each). This is the first time in the world that terabit-class communication has been realized using terminals miniaturized enough to be mounted on satellites or HAPS.

Moving forward, NICT plans to further miniaturize the terminals for implementation onboard a 6U CubeSat. NICT aims to conduct free-space optical communication demonstrations at speeds of up to 10 Gbit/s between a Low Earth Orbit (LEO) satellite (altitude approx. 600 km) and the ground in 2026, and between a satellite and HAPS in 2027. Through these experiments, NICT will demonstrate compact, ultra-high-speed data communication capabilities and pave the way for the realization of Beyond 5G/6G Non-Terrestrial Networks (NTN).

To address the global environmental and climate crisis and advance the UN SDGs, it is essential to fully leverage Earth observations (EO) through the integration of atmospheric, hydrological, cryospheric, lithospheric, ecological, and socio-economic data. Based on discussions from the 2023 “Towards Global Earth Observatory” workshop, this paper highlights the fragmented nature of current EO and data repositories and emphasizes the need for a more coordinated global Ground-Based Earth Observatory (GGBEO). We summarize the status of key in-situ and ground-based remote sensing systems and outline the actions required to build an integrated GGBEO with interoperable data repositories, unified observation networks, and sustainable long-term support.

The first exoplanet ever discovered in 1995 was what we now call a “hot Jupiter”, a planet as massive as Jupiter with an orbital period of just a few days. Today, hot Jupiters are thought to have formed far from their stars—similar to Jupiter in our Solar System—and later migrated inward. Two main mechanisms have been proposed for this migration: (1) high-eccentricity migration, in which a planet’s orbit is disturbed by the gravity of other celestial bodies and subsequently circularized by tidal forces near the star; and (2) disk migration, in which the planet moves gradually inward within the protoplanetary disk.

However, it is not straightforward to distinguish the mechanism a particular hot Jupiter experienced from observations alone. In the case of high-eccentricity migration, the gravitational perturbations can tilt the planet’s orbital axis relative to the star’s rotational axis, resulting in a measurable misalignment. However, tidal forces can realign these axes over time, meaning that an aligned orbit does not necessarily imply disk migration. As a result, there has long been no reliable observational method to identify planets that formed through disk migration.

To address this challenge, a research group led by PhD student Yugo Kawai and Assistant Professor Akihiko Fukui at the Graduate School of Arts and Sciences, the University of Tokyo, proposed a new observational method that takes advantage of the timescale of high-eccentricity migration itself.