The dangers of "sunlight as a service"

Image credit: RSC Energia (CC BY 4.0​)
1585 words / 6-minute read

Light pollution is increasing over much of the world. It is a trend that goes back decades and shows no sign of slowing down. We wrote here about the situation as recently as early 2023. At that time, new research showed that skyglow was then increasing at a worldwide average rate of 10 percent each year. A much newer notion is the idea of 'light pollution' from space. We also wrote about that situation in 2023. The concern was then about the changing appearance of the night sky. 

Fast forward only two years, and a completely new concern is now emerging. What happens when satellites can turn night into day? The result is a novel threat we explore in this month's post.

New technologies for 'New Space'

We live in an era some that some call "New Space". This describes activities in outer space dominated by private commercial actors. It contrasts with previous decades when only national space programs could pay the high cost of launch.

That cost plummeted in the 2010s, enabling private companies to launch payloads into space. At first, the main service private satellites provided was global telecommunications. But as investor money poured into the industry, entrepreneurs began to come up with audacious new ideas.

One of those ideas is to harness solar power in space and send it to the ground. This takes different forms including converting sunlight to radio waves. A simpler concept would deploy large reflective surfaces in orbit around the Earth. These would redirect sunlight to the ground to illuminate solar power stations on the ground. The scheme only works near sunrise and sunset, when the reflectors are in sunlight but the sun has set on solar farms.

Proponents of this technology note that it can provide light for other uses. For instance, they say, it could function in place of street lighting over cities. It would provide an illumination level about four times the brightness of full moonlight. That could aid in disaster recovery when utility power is unavailable.

An old idea reborn

You would be forgiven for thinking this is the first time anyone has proposed such a thing. But it's not. In the Second World War, a group of German scientists at the German Army Artillery proposed building a Sonnengewehr ("sun gun"). They designed a focused beam of sunlight from an orbital reflector as an offensive weapon. And they expected the devastation to be akin to what the world later saw resulting from the U.S. atomic attack on Japan.
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In October 1992, the Russian Federal Space Agency launched the Znamya 2 satellite. Designed as a 'solar sail' testing a new kind of propulsion, the RFSA repurposed it as a 20-meter-wide solar mirror. It consisted of panels of stretched, highly reflective film that deployed after launch.

During a demonstration of the technology, it successfully directed a beam of sunlight to the ground. It yielded a spot 5 kilometers wide with the intensity of full moonlight. The beam swept across Europe from southern France to western Russia at a ground speed of 8 kilometers per second. Though weather along much of the ground track was cloudy, some observers reported seeing bright flash of light as the beam swept past them.

The RFSA tried another test of this technology in 1999 with a larger spot size and a brighter beam. The test failed when the reflective film panels tore after snagging a piece of the Progress spacecraft used to deploy the object. Although the RFSA planned future satellites with even large collecting surfaces, the 1999 failure was the death knell for the program.

More than 25 years later, the concept is again inching closer to reality. An American company called Reflect Orbital applied for clearance to launch and operate a test satellite in 2026. It consists of a thin-film reflector 18 meters on a side and a system to control its orientation in space. By changing that orientation relative to the direction of the Sun, it can direct a beam of sunlight toward Earth.

Like Znamya 2, its beam has a diameter of 5 kilometers on the ground, enough to illuminate a large solar power installation. The beam shines for about four minutes before the satellite disappears over the local horizon. The company plans to eventually launch a flotilla of thousands of these reflectors. That would enable continuous sunlight for about an hour after dusk and an hour before dawn.

The hazards of sunlight at night

Will it work? We don't yet know. The Russian test from the 1990s suggests that something like this is technically workable. But if it does, a host of concerns are expected to follow.

Some problems have to do with the idea of shining a beam of light with the intensity of sunlight onto specific locations at night. A simple calculation suggests that the reflectors will appear on the sky as sources several times brighter than a full Moon. Far from the beams, they'll still look like bright stars, and dozens of them may appear in the sky at any moment.

Scattering of light in the atmosphere will make the edges of the beams 'fuzzy'. The mirror-like surfaces of the reflectors will deteriorate with time due to exposure to the space environment. The beams of light they produce becoming more diffuse, spreading out and losing intensity. This may direct light well away from the intended targets of the beams. Some of that light may end up in ecologically sensitive areas.

As described above, the mirrors have to change their orientation in space as they pass over a given location. Although the company claims that the reorientation will happen quickly, it involves sweeping the light beam across the Earth at high speed. A 2000 study published in the Journal of the Royal Astronomical Society of Canada found that "space-mirror experiments reflecting sunlight to Earth can produce resolved images having surface-brightness sufficient to damage human eyes looking through telescopes or binoculars". Even if the flash is instantaneous, it could cause real harm to the viewer.

In a similar vein, these light beams could be a problem for aviation safety. Pilots have for years reported intense flashes of light from laser pointers on the ground shining up at their planes. At the altitudes of commercial planes, beams of sunlight from space will be larger in size and brighter than they appear on the ground. This could become a significant hazard for civilian and military pilots alike.

There is great potential for misuse of this technology. Sunlight could be weaponized in a way that conventional solar power cannot be. It may be directed toward people and communities that don’t want it. It could also be used to convey battlefield advantage in military conflicts. This adds another layer of complexity in deciding how the technology should be regulated.

The reflective material could be subject to fraying or other kinds of damage on orbit. They may shed material that becomes space debris. Over time, the satellites will inevitably fall back to Earth, whether from atmospheric drag or deliberate action to de-orbit them. Where, when and how they will come back down is not clear.
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Lastly, despite prognostications to the contrary, there is no “inevitability” about this or any other idea for furthering renewable energy sources through methods such as sunlight as a service. Improvements in battery storage are slowly improving renewable energy supplies at night. We may be better off deploying more solar panels on the ground, even knowing that there is a life-cycle cost for producing/recycling the equipment. 

An unproven future

"Greenwashing" is a label describing efforts made to persuade the public that an organization's products or actions are friendly to the environment. Usually they are not, and the greenwashing effort is deceptive.

That seems to be happening in the case of sunlight as a service. The sales literature is full of starry-eyed claims having to do with a purported social good. But it focuses on the notion of sustainability in a narrow sense: providing sunlight from space for "clean" electricity generation. It doesn't consider the full lifecycle of the project from launch to de-orbit.

It doesn't account for the negative externalities of directing light to spaces where it doesn't naturally exist at night. There is abundant evidence for the harms associated with artificial light at night. That in principle includes sunlight directed to the night side of Earth. It interferes with natural rhythms as much as sources of electric lighting.

At the same time, there is no national or international prohibition on this kind of activity in outer space. The international legal framework governing activities in space takes the view that 'what isn't forbidden is allowed'. Norms often change to discourage a harmful activity only when the harm has already been inflicted.

In that sense it resembles obtrusive space advertising, which we wrote about here recently. Dangerous activities in space can occur with only an ill-defined liability system on the other side.

It's unclear how serious any of this is, and projects like Reflect Orbital may not fly at all. Many such audacious ideas never become reality. Some are meant only to attract the intention of investors looking to make quick money as companies are bought and sold.
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It remains to be seen whether there is any successful business model for selling "sunlight as a service". Yet the lure of new wealth from space may prove irresistible. This is a challenge for defenders of the night everywhere, and one that is worth watching closely.