Overview: A Bold, Controversial Idea
A US startup called Reflect Orbital is proposing a strikingly ambitious plan: beam sunlight from space to Earth to power solar farms after sunset. The concept hinges on giant mirrors in orbit that reflect solar energy down to specific ground locations, potentially enabling round-the-clock solar power. The project could begin with an 18-meter test satellite named Earendil-1, with a long-term target of thousands of satellites in orbit by 2030. The idea, at first glance, sounds like a high-tech solution to the intermittency problem facing renewable energy. But it has sparked a heated debate among astronomers, policymakers, and climate advocates about light pollution, sky brightness, and practical viability.
How It Would Work—and Why Scaling Is the Challenge
The envisioned system uses mirrors to reflect daylight onto solar farms. In principle, this is similar to bouncing sunlight off a watch face onto a distant wall, except the scale is vastly larger. A satellite roughly 625 kilometers above Earth would, with mirrors as large as 54 meters, cast a daylight-like beam toward a ground patch. However, the Sun’s half-degree angular size means the reflected beam, even from a curved mirror or lens, spreads as it travels. At about 800 kilometers distance, the illuminated patch could be around 7 kilometers wide, making a tight, bright pinpoint impossible.
In numeric terms, a single 54-meter satellite could deliver about 15,000 times fainter than the noonday Sun to the surface. That’s still brighter than the full Moon, raising concerns about glare and sky glow. To reach roughly 20% of noon sunlight (about 200 watts per square meter) for a solar farm, hundreds to thousands of satellites would be required. Even then, the orbital dynamics pose a constraint: a satellite moves quickly across the sky, remaining within range for only minutes before another location becomes illuminated. The plan to deploy hundreds of thousands of mirrors raises questions about feasibility and cost.
Technological Trials and Realistic Expectations
Reflect Orbital has publicly shared a balloon-based test where a 2.5-meter square mirror directed light onto solar panels, delivering around 516 watts per square meter at 242 meters distance. While promising on a small scale, extrapolating to space introduces substantial uncertainty. A practical space-based system would need an enormous, expensive constellation and robust daylight-path accounting to meet energy targets amid cloud cover and day-night cycles. The founders have floated scenarios with 250,000 satellites in sun-synchronous, day-lit orbits, a plan that would dwarf current space traffic and debris concerns. Critics warn such a constellation could illuminate the night sky, complicating astronomical observations and harming nocturnal ecosystems.
Astronomical and Environmental Concerns
Light pollution is not a mere nuisance for stargazers. It can hinder telescope observations, distort data, and even influence animal behavior and circadian rhythms. If a large fraction of the night sky brightens due to deliberate space-based mirrors, observatories could lose precious dark time needed for research. In addition, the sheer number of reflective surfaces could create unpredictable lighting flashes as satellites move, potentially washing out star fields or affecting long-exposure astronomical imaging. Environmental groups and space agencies are watching closely to assess risks and possible mitigations, such as targeted illumination avoidance zones and improved orbital planning.
What Comes Next—and What It Would Take
Whether Reflect Orbital’s plan moves beyond concept depends on a mix of regulatory clearance, technical milestones, and independent risk assessments. The company argues its approach could be brief, predictable, and targeted, avoiding observatories and sharing satellite locations to help scientists plan. Critics remain skeptical about the practicality and the cumulative light impact on the night sky.
As space becomes more congested, the implications of introducing thousands of reflective satellites are profound. Even if the system delivers a fraction of the sunlight intended, the aggregate effect on astronomy, climate science, and nocturnal ecosystems could be substantial. The coming years will reveal whether the promise of “sunlight on demand” can survive rigorous scrutiny and real-world constraints.
Bottom Line
Reflect Orbital’s concept highlights a broader tension in the renewable energy transition: the drive for continuous power must be balanced against preserving the night sky and protecting astronomical science. The debate is far from over, but the questions about light pollution, feasibility, and governance will define the trajectory of any large-scale space-based lighting scheme.
