Japan’s OHISAMA demonstration satellite is scheduled for launch in fiscal 2026, embarking on an ambitious mission to wirelessly deliver solar power from space to Earth for the first time. Unlike earlier experiments that only detected signals, OHISAMA aims to generate usable electricity, marking a potential milestone in the development of space-based solar power (SBSP). The satellite will ride aboard Space One Co.’s Kairos 5 small rocket.
SBSP technology involves placing solar collectors in orbit to capture sunlight, convert it into electricity, and transmit the energy wirelessly—typically by microwave—to receiving stations on Earth. This method bypasses weather fluctuations and the day-night cycle, giving it a distinct advantage over terrestrial solar and wind power. In addition, the technology offers the flexibility to redirect energy to areas experiencing natural disasters or spikes in demand.
Japan Space Systems (J-spacesystems), a nonprofit R&D foundation commissioned by the Ministry of Economy, Trade, and Industry, has proposed deploying massive 2.5-kilometer-square solar arrays in geostationary orbit 36,000 kilometers above Earth. Energy generated in orbit would be transmitted via microwaves to a 4-kilometer-diameter ground antenna and then fed into the national power grid. A single SBSP unit could theoretically produce around 1 gigawatt of electricity, enough to supply over 10 percent of Tokyo’s annual consumption.
The OHISAMA satellite itself, weighing 180 kilograms, carries a power-generation and transmission panel measuring 70 centimeters by 2 meters, with a generating capacity of 720 watts. The mission’s immediate goal is modest: to transmit power from a 450-kilometer orbit to a 64-meter parabolic antenna at JAXA’s Usuda Deep Space Center in Nagano Prefecture and light an LED, demonstrating successful conversion of space-based microwaves into usable electricity. This follows a 2024 aircraft-based test at 7 kilometers altitude.
SBSP faces technical hurdles, including minimizing beam spreading caused by diffraction and maintaining precise phase control. Japan has developed extensive expertise in microwave power transmission and retrodirective beam pointing, in which the ground receiver guides the satellite’s microwave beam. Other nations, including the United States, China, and European countries, are also accelerating SBSP research, with military and commercial applications under consideration.
If OHISAMA successfully delivers electricity to Earth, it would be the first operational demonstration of its kind and could pave the way for commercialization by the 2040s. Future applications could include supplying power to lunar exploration missions. The launch, however, depends on the reliability of Space One’s Kairos rockets, following prior setbacks.
“Technologically, Japan is leading the world in this field,” said Hiroki Yanagawa, senior executive at J-spacesystems. The project not only aims to transform clean energy production but also to cement Japan’s position at the forefront of space-based solar power innovation.
