Every night, as telescopes around the world open their domes to study the cosmos, astronomers are forced to contend with an unexpected form of pollution: bright white streaks slicing across their images.
Author
- Noelia Noël
Senior Lecturer, School of Mathematics and Physics, University of Surrey
These luminous trails are caused by satellites. Specifically, the growing number of "megaconstellations" launched into low Earth orbit (LEO). These mega-constellations consist of many, sometimes hundreds, of satellites. They are intended to work as a system, providing services such as global internet access. Commercial companies that operate mega-constellations include SpaceX, Amazon and OneWeb.
The streaks in astronomy images aren't just cosmetic. They can corrupt sensitive astronomy data, generate false signals, and even trigger alerts for events that never happened.
There may now be a partial solution to the luminous trails vexing astronomers. An ultra-black coating could be applied to the satellites themselves, dimming the trails that they leave in images. This material, called Vantablack 310 , absorbs more than 99.99% of visible light.
Modern astronomical observations rely on long exposure imaging, collecting faint light from distant galaxies, exoplanets, or supernovae over several minutes or hours. When a satellite crosses the field of view during that time, it reflects sunlight into the telescope, creating a saturated streak across the image.
The impact is already substantial. Researchers at the Vera C Rubin Observatory in Chile - a flagship survey telescope set to revolutionise our understanding of the Universe - estimate that over 30% of the telescope's twilight images already contain at least one satellite trail. And it's not only visible light astronomy that's at risk.
Radio telescopes, infrared detectors, and even gravitational wave observatories are reporting increasing interference from satellites - including reflected light, unwanted radio emissions, and other forms of contamination. The ultra-black coating won't alleviate these issues, of course. Other solutions will need to be found for these other forms of interference.
A crowded sky
With more than 16,000 active satellites already in orbit and tens of thousands more planned, the skies are becoming increasingly congested. While these constellations offer enormous benefits, including global internet access, disaster response, agricultural monitoring, and climate surveillance, they also threaten the clarity of astronomical observations.
Satellites in low Earth orbit (typically 500km-600km altitude) are often visible to the naked eye shortly after sunset or before sunrise. For sensitive telescopes, they can be ten to 100 times brighter than the recommended limits set by the International Astronomical Union.
I am one of a team of researchers at the University of Surrey that is exploring Vantablack 310 as a next generation coating to reduce satellite brightness. The trials are being carried out by UK scientists in partnership with the Surrey Space Centre, and materials innovators Surrey NanoSystems.
Originally developed for high-contrast optical systems - such as instruments that need to spot faint signals next to very bright ones - the coating absorbs more than 99.99% of visible light.
In 2026, Vantablack 310 will be tested in orbit for the first time aboard Jovian 1 , a CubeSat - a small satellite about the size of a cereal box. It was developed at the University of Surrey and launched as part of the UK's Jupiter programme, a university-led initiative that trains students in real-world satellite design, testing and operations, while supporting cutting-edge space research.
The mission will assess how the coating performs under the harsh conditions in space, such as temperature swings, ultraviolet radiation, and micro-meteoroid impacts. If successful, it could significantly reduce how bright satellites appear to telescopes - making the streaks they leave behind much fainter and easier to remove from astronomical images.
Ultra-black coatings will not make satellites invisible. Even the darkest object in orbit will reflect some light. But the goal is not invisibility - it is compatibility. Reducing satellite brightness below key thresholds ensures that scientific observations remain viable.
What's at stake is more than just clean astronomical data. The night sky is one of humanity's oldest shared resources - a source of scientific insight, cultural heritage, and spiritual meaning across time and geography. From the star lore of indigenous people to ancient navigation systems, the night sky has always helped us understand our place in the universe.
Publicly funded observatories in lower income countries - where many of the world's darkest skies still exist - are also disproportionately affected, despite those countries having little say in the decisions that affect their skies.
Framing the issue solely as a technical inconvenience for elite institutions misses the point. This is also about equity, access, and environmental justice. Who gets to access the sky, and who decides how it is altered, are global questions that demand inclusive solutions.
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This project was funded with six months of support from the Research England Development Fund (UKRI), focusing on mitigating satellite light pollution, including the in-orbit testing of ultra-black coatings.
