CubeSOTA mission  
：Miniaturized Lasercom Terminal in Low Earth Orbit

The CubeSOTA (CubeSat Small Optical Transponder) mission will use a 6U CubeSat (30 × 20 × 10 cm) to validate a miniaturized free-space laser communication terminal in space. This will be the first in-orbit validation of the terminals developed by NICT in recent years. Following the successful SOTA (Small Optical TrAnsponder) mission a decade ago, the CubeSOTA mission aims to demonstrate bidirectional optical links in low Earth orbit (LEO) at data rates of up to 10 Gbit/s using a variety of innovative lasercom technologies. It is scheduled to be launched in fiscal year 2026 on a SpaceX Falcon 9 rocket.

Research overview: Developing Technologies to Establish High-Speed Satellite Communications

Mission Objectives:
The mission focuses on two main communication scenarios:

1. LEO-to-Ground: Establishing 10 Gbit/s lasercom links with Optical Ground Stations (OGS) in Japan and overseas.
2. LEO-to-HAPS: Demonstrating lasercom links with a High-Altitude Platform Station (HAPS) in the stratosphere (~20 km).

Research overview: Developing Technologies to Establish High-Speed Satellite Communications

Research overview: Developing Technologies to Establish High-Speed Satellite Communications

Technical specifications:
The CubeSOTA lasercom payload occupies ~3U of volume and has a total mass of ~4 kg. Its key technical components include:

• Gimbal-Less Coarse Tracking: Coarse tracking is handled directly by the satellite bus attitude determination and control system (ADCS) in a closed loop with a 3-cm-aperture coarse tracking sensor.
• 9-cm Cassegrain Telescope: Enables a narrow beam divergence of ~20 µrad FWHM, the narrowest ever transmitted from a CubeSat lasercom terminal, and maximizes the collection of uplink light.
• Beam Divergence Control (BDC): this system can control beam divergence to facilitate initial link acquisition and adapt to distance and pointing requirements.
• High-Power Vacuum MEMS Mirrors: Two tip-tilt MEMS mirrors for fine pointing and point-ahead angle correction customized to steer a high-power small optical beam in a vacuum while preserving wavefront quality.
• Integrated EDFA Module: A 2-in-1 miniaturized optical amplifier unit housing a 2-W high-power amplifier (HPA) for the transmitter and a low-noise preamplifier (LNA) for the receiver.
• 10G Modem: Integrates FEC, interleaving, 1 TB of internal memory for store-and-forward operation, a real-time loopback mode, and a variable data-rate function (1 to 10 Gbit/s).
• Full-Duplex: Capability to transmit and receive at 10 Gbit/s, aiming to demonstrate, for the first time, a LEO lasercom uplink based on SMF coupling + optical amplification.