December 6, 2023

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Marco Langbroek fights against light pollution caused by satellites

Marco Langbroek fights against light pollution caused by satellites

“Look, this is where I put my camera,” explains Marco Langbroek. We are standing at the pivot window in the attic of his apartment in the center of Leiden. When the window is horizontal, his sky camera fits snugly into it. “It’s a little cramped, but you have a nice view south.”

Most astronomers use more advanced and, above all, more sensitive equipment, to discover celestial phenomena that may be invisible in the city center with all its lights. But Langbroek, a lecturer in space situational awareness (SSA) at the School of Aeronautical and Astronautical Engineering at Delft University, wanted to show just how bright a celestial object can be.

BlueWalker 3, an experimental satellite launched in 2022, reached magnitude 0, comparable to the brightest stars, Langbroek and 39 other researchers wrote. In a post in nature.

Bright moving dot

Langbroek says this is of great concern to astronomers, because the satellite from the American company AST Spacemobile is only an experimental satellite. “The idea is that at least 243 will be launched. They are intended to allow you to make direct calls to the satellite using your regular mobile phone, and this requires a large antenna of 64 square metres.

The antenna reflects sunlight captured by the satellite at an altitude of about five hundred kilometers, while it is already dark on Earth, resulting in a moving bright spot in the sky. “It’s annoying,” says Langbroek. “Astronomical images can become unusable due to satellites appearing unexpectedly. In some cases, telescope sensors can be temporarily or permanently damaged.

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This problem can still be solved with one or a group of satellites, but if the sky becomes filled with thousands of artificial stars, astronomical observations from Earth will become impossible.

But this is not only of interest to astronomers, says Langbroek. “You have changed the appearance of the starry sky, and it belongs to all of us. Many cultures have stories, songs and legends associated with the starry sky. That paradise is taken without anyone asking anything, and no one can get out of it.”

Astronomers were surprised by massive artificial stars in 2019, when the American space company SpaceX launched its first Starlink satellites, aiming to provide global internet. In the end there should be 42,000.

When astronomers sounded the alarm, SpaceX promised to investigate what they could do about light pollution. Dark coating reduces reflection slightly. However, these appear to be just temporary measures, as other companies such as OneWeb, Amazon and a number of Chinese companies also have plans to create more satellite constellations totaling tens of thousands of satellites.

“The legislation lags behind the facts,” says Langbroek. The International Astronomical Union (IAU) makes recommendations for maximum brightness, but BlueWalker exceeds this by a factor of one hundred.

Coffee making machine

Langbroek says stakeholder engagement is essential. “They are astronomers, but in reality we are all. The problem is that agreement on international law often takes decades, and then we are really too late. Then those satellites already exist. There is more hope for national legislation in the United States.” , where most divorced companies are located.

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What might also help is making satellite orbit parameters known. “Then astronomers can block the light or turn off sensitive sensors at the right time.” But the US military component that maintains a public satellite database is often days behind the times. And the parameters published by SpaceX itself are often incorrect. “Then they maneuvered their satellites again.”

So astronomers want to observe the satellites themselves. “This requires more tracers,” says Langbroek. In his apartment in Leiden there is a prototype of such a gadget: a camera the size of a coffee machine, which will be placed on the roof of the Aerospace College in Delft.