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A peer-reviewed number for orbital glare turns Reflect Orbital's demo into a regulatory test
A paper accepted by Astrophysical Journal Letters puts the spill from Reflect Orbital's beams at 80 kilometers. The FCC approved the demonstration satellite in July.
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What happened
- Later this year, US company Reflect Orbital plans to launch a test satellite called Eärendil-1 that will extend an 18-by-18-meter mirror in orbit.
- Reflect Orbital's plans involve launching up to 50,000 larger satellites, measuring 54 by 54 meters, to reflect sunlight to Earth on demand.
- The launch was approved by the Federal Communications Commission in July.
- Reflect Orbital has said the goal is to prolong the hours of sunlight for uses including solar panel charging, emergency response, and military activities.
- Miroslav Kocifaj, an astronomer at the Slovak Academy of Sciences, and colleagues calculated how far light beamed to the ground would scatter, in a paper published online and accepted for publication in Astrophysical Journal Letters.
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Why it matters
A paper accepted for publication in Astrophysical Journal Letters puts figures on how far Reflect Orbital's beamed sunlight would spread past the customer who ordered it, concluding that a combined beam aimed at a patch five kilometers across would still be visible as a glow above the horizon up to 80 kilometers away [6][17]. That matters because the Federal Communications Commission approved the company's demonstration launch in July, which makes the test satellite the first practical case of whether orbital brightness is regulated by anyone at all [3][1].
The numbers are the point. Miroslav Kocifaj of the Slovak Academy of Sciences and colleagues calculate that inside the intended five-kilometer target circle, one satellite would appear roughly 40 times brighter than the full moon, and that at 14 kilometers from the beam center it would still be as bright as the full moon [6][15][16]. That second figure describes an area about 31 times larger than the zone being sold light [20]. The 80-kilometer glow radius covers something on the order of a thousand times the target area [21]. Kocifaj's summary is that the damage extends far beyond the target area [7].
Scale compounds it. Combining 400 satellites, which the company eventually plans to do, would produce light as bright as 10,000 full moons inside the five-kilometer patch, or 2.4 percent of the brightness of the sun [14]. Those 400 are 0.8 percent of the up to 50,000 satellites, each 54 by 54 meters, that Reflect Orbital says it wants to fly [2][19]. The satellite launching this year, Eärendil-1, carries an 18-by-18-meter mirror [1]. The stated uses are prolonging daylight for solar panel charging, emergency response, and military activity, from highly inclined near-polar orbits that catch sunlight before sunrise and after sunset [4][12].
CEO Ben Nowack disputes the paper, saying some assumptions are simply inaccurate and that the company's safeguards, including exclusion zones, already account for scattering [10]. He says Reflect Orbital has engaged substantively with astronomers, environmental researchers, and scientists, and that their feedback has informed its technology and operational plans [18]. Kocifaj's response is that the company has published no numbers, no description of its model, no assumptions, and no data, leaving nothing to engage with technically [11]. Olivier Hainaut of the European Southern Observatory, who previously modeled the beams as brightening the sky worldwide by up to 300 percent, says the new results are unsurprising but useful and that the modeling group knows what it is doing [8][9]. Samantha Lawler of the University of Regina puts the astronomy position flatly: this is incompatible with dark skies [13].
The regulatory question is now live. In August a group including DarkSky International and the American Bird Conservancy asked the FCC to review its approval of Eärendil-1, raising aviation and wildlife effects alongside astronomy [5].
Watch whether the FCC treats brightness as within its remit or as outside a licensing decision made on spectrum grounds [3][5]. Watch whether Reflect Orbital publishes a scattering model with numbers rather than assurances, since that is the only thing that would settle the dispute on its merits [10][11]. And watch the demonstration itself: a single 18-meter mirror is a measurable object, and ground measurements of its glare will either support or undercut the 40-moons figure before the constellation is built [1][15].
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- [1]
Later this year, US company Reflect Orbital plans to launch a test satellite called Eärendil-1 that will extend an 18-by-18-meter mirror in orbit.
- [2]
Reflect Orbital's plans involve launching up to 50,000 larger satellites, measuring 54 by 54 meters, to reflect sunlight to Earth on demand.
- [3]
The launch was approved by the Federal Communications Commission in July.
- [4]
Reflect Orbital has said the goal is to prolong the hours of sunlight for uses including solar panel charging, emergency response, and military activities.
- [5]
In August, a group of organisations including DarkSky International and the American Bird Conservancy urged the FCC to review its approval of the Eärendil-1 satellite, highlighting potential negative consequences for aviation and wildlife as well as astronomy.
- [6]
Miroslav Kocifaj, an astronomer at the Slovak Academy of Sciences, and colleagues calculated how far light beamed to the ground would scatter, in a paper published online and accepted for publication in Astrophysical Journal Letters.
- [7]
Kocifaj says deploying these mirrors would be seriously damaging for astronomy and for the nighttime environment, and that the damage extends far beyond the target area.
- [8]
Olivier Hainaut, an astronomer at the European Southern Observatory in Germany, says the paper's results are not surprising but are still useful, and that the authors are really good at that kind of modeling and know what they are doing.
- [9]
Hainaut had previously modeled the broader effect of Reflect Orbital's beams, finding they would brighten the sky up to 300% worldwide.
- [10]
Reflect Orbital CEO Ben Nowack disagrees with the findings of Kocifaj's paper, saying some assumptions are simply inaccurate and that the company's safeguards, including maintaining exclusion zones, take account of scattering.
- [11]
Kocifaj says Reflect Orbital has not provided data to back up its claims, giving no numbers, no description of the model, no assumptions and no data, so there is nothing that can be engaged with technically.
- [12]
Reflect Orbital intends to place satellites in highly inclined orbits, almost pole to pole, to reflect sunlight in the hours before sunrise and after sunset, and eventually wants satellites high enough to provide light 24-7.
- [13]
Samantha Lawler, an astronomer at the University of Regina in Canada, says this is incompatible with astronomy and that there is no way to do it and preserve dark skies.
- [14]
Combining the beams of 400 satellites, which Reflect Orbital eventually plans to do, would yield light as bright as 10,000 full moons within the five-kilometer area, or 2.4% as bright as the sun.
- [15]
Within the beam's target area, intended to be a circular patch five kilometers across, a single Reflect Orbital satellite would appear about 40 times brighter than the full moon.
- [16]
As far as 14 kilometers from the center of the beam, a single satellite would still be as bright as the full moon.
- [17]
Kocifaj and colleagues calculated that even up to 80 kilometers away, the combined beam would be visible as a glow above the horizon.
- [18]
Nowack says the company has engaged substantively with legitimate concerns raised by astronomers, environmental researchers, and scientists, and that their feedback has informed its technology and operational plans.
ReportedContestedSource: Ben Nowack, CEO of Reflect Orbital2 sources— create a free account to open themView cited source - [19]
The 400 satellites used in the 10,000-full-moon calculation represent 0.8 percent of the up to 50,000 satellites Reflect Orbital plans.
- [20]
The circle within which a single satellite is at least as bright as the full moon (14 km radius) covers about 31 times the area of the intended 5-km-wide target patch (2.5 km radius).
- [21]
The 80-kilometer radius out to which the combined beam remains visible as a horizon glow covers roughly 1,000 times the area of the intended 5-km-wide target patch.
Sources
1 independent publisher whose own reporting we read for this story.
- technologyreview.comThis company’s plans to deploy space mirrors could jeopardize the night sky for many
2 articles · August 21, 2026
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- European Southern ObservatoryFollow
- Reflect OrbitalFollow
- Ben NowackFollow
- US Federal Communications CommissionFollow
- Michelle HanlonFollow
- National Environmental Policy ActFollow
- MIT Technology ReviewFollow
- Slovak Academy of SciencesFollow
- University of ReginaFollow
- The Astrophysical Journal LettersFollow
- Miroslav KocifajFollow
- DarkSky InternationalFollow
- Olivier HainautFollow
- American Bird ConservancyFollow
- Eärendil-1Follow
- Samantha LawlerFollow