An American startup wants to revolutionize solar energy with satellites that reflect sunlight at night — but the idea worries scientists and environmentalists

The promise sounds like something out of a science fiction movie: provide solar power at night by means of satellites orbiting the Earth. The ambitious idea comes from the American startup Reflect Orbital, which aims to use giant space mirrors to redirect sunlight to photovoltaic plants after sunset.

The proposal, however, has divided opinions between innovation enthusiasts and astronomers concerned about the impact of the so-called artificial light pollution. According to experts, the project could interfere with astronomical observations and even affect the behavior of nocturnal species.

Reflector satellites: how the Reflect Orbital project would work

According to the company, the first phase of the project will be launched in 2026 with the test satellite Earendil-1, an 18-meter diameter reflector. The goal is to evaluate the ability to redirect sunlight to specific points on Earth, allowing solar power plants continue generating electricity even at night.

The plan is bold: by 2030, Reflect Orbital hopes to place around 4.000 satellites in orbit. Each of them would be approximately 625 km from the Earth’s surface, equipped with mirrors capable of reflecting part of the solar radiation towards previously selected regions.

However, initial calculations show that the light reflected by a single satellite would be 15 times dimmer than the midday sun, although still brighter than the light of the full moon. To achieve only 20% of solar intensity, would be necessary about 3.000 satellites operating in sync — an unprecedented technical and logistical challenge.

The balloon test: first steps of a gigantic idea

Before taking the concept to space, the company’s founder, Ben Nowack, performed a preliminary experiment. In a test with a hot air balloon, a 2,5 meter flat mirror was used to reflect sunlight onto photovoltaic panels.

The result was impressive: the team measured 516 watts per square meter — about half the power received under the midday sun, which reaches on average 1.000 watts per square meter.

But there’s a problem: scale. To replicate this performance in orbit, the mirror would need to have 6,5 km wide, covering 42 square kilometersAccording to astronomers, it would be unfeasible to build something so gigantic in space with current technology.

Solar energy at night: a viable promise or an expensive dream?

Reflect Orbital argues that its goal is more modest: to generate 200 watts per square meter, equivalent to 20% of full solar energy. Even so, the challenge remains enormous.

A satellite at an altitude of 625 km moves at 7,5 km per second, remaining visible over the same region for only three and a half minutes. This means that to keep an area lit for a continuous hour, it would be necessary thousands of additional satellites, orbiting in perfect synchrony.

In a recent interview, Nowack even suggested that the company intends to launch 250 thousand satellites by the end of the decade. This constellation would be larger than the total number of satellites and space debris currently cataloged.

Astronomers warn: the price could be the night sky

The scientific community reacted with strong concern. Astronomers from several countries argue that the initiative threatens the observation of the Universe and could cause irreversible damage to optical astronomy.

“A mirror constellation of this type would be devastating for astronomy,” experts warn. The problem is that, even if the test satellite performs as expected, it could be brighter than the full moon, interfering with astronomical observations and professional telescopes.

Furthermore, reflected light could pose safety risks to scientists. The surface of each mirror, the researchers point out, “could be almost as bright as the Sun,” posing a safety risk. permanent damage to vision of those who use telescopes without adequate filters.

Environmental and biological impacts under analysis

Light pollution doesn’t just affect observatories. Several studies show that artificial light at night disrupts the biological rhythms of night animals, alters reproductive cycles and interferes with bird migration.

Astronomers also point out that even if satellites were only used to illuminate solar power plants, its light beams would end sweeping other areas of the planet as they move. The result would be a night sky constantly crisscrossed by bright flashes, visible to the naked eye all over the world.

Reflect Orbital’s response to criticism

When asked about environmental and scientific concerns, Reflect Orbital said in a statement to Bloomberg that the satellites will reflect light in a way “brief, predictable and targeted”, avoiding interfering with astronomical observatories.

The company also committed to share the coordinates of your satellites so scientists can adjust their observation schedules. Still, the scientific community maintains reservations, claiming that the promise is difficult to fulfill given the number of planned satellites.

So far, the startup has not responded to requests for comment from other specialized publications.

The concept of nighttime solar energy is seductive — especially in a world that seeks to accelerate energy transition and reduce dependence on fossil fuels. However, the Reflect Orbital case shows that innovation and sustainability must go hand in hand.

Even if the project manages to demonstrate technical feasibility, there are practical and ethical hurdles to overcome. Launch costs, environmental impacts, and the management of thousands of satellites in orbit pose challenges that go beyond the realm of engineering and enter the realm of global public policies.

Currently, the light pollution is already a growing problemIt is estimated that the number of satellites visible in the night sky has increased exponentially in the last decade, mainly with the advancement of private communications constellations. If Reflect Orbital moves forward with its proposal, the number of objects reflecting light in space could multiply tenfold.