For years, the astronomical community has looked at the sky with considerable concern from Earth. And it’s normal. In recent years, the number of satellites that we have put into orbit has grown exponentially, highlighting above all starlinkwhich promised to bring the internet to the entire planet in exchange for fill our nights with “trains of lights”. But this is only hindering our ability to continue investigating the universe where we are immersed.
Trapped in a cage. The telescopes that we now have closer to Earth to do their work logically have to look towards our sky. The problem, as the research points out led by Alejandro S. Borlaff, is that they are going blind. Specifically, the low orbit (LEO) space telescopes that are not only not safe, but they are trapped in a real cage that prevents them from seeing further.
Until now, it was possible to think that satellite traces could only affect terrestrial observatories. However, orbital reality is pure geometry: most large space telescopes like Hubble They orbit at about 540 km high. A height at which the internet megaconstellations that are located above or in the layers that range from 340 km to 8,000 km.
Because. Satellites do not emit any type of light and should not cause problems. But the problem comes when they reflect sunlight, and when this happens in the new coverage satellites that have a large size, we find that even if it is night on Earth (or wherever the telescope is), at a hundred kilometers high the Sun continues to illuminate the satellite.
And the lighting and telescopes they get along very badly. Space telescopes are designed to look at objects that are “still” at infinity (stars, galaxies). To capture its faint light, the telescope must fix its gaze on an exact point and not move. However, satellites move at thousands of kilometers per hour in relation to the telescope and since the camera shutter is open for a long time (long exposures of minutes or even hours) to capture weak light, the satellite crosses the entire frame during the photo, being recorded not as a point, but as a continuous line or “scar” of light.
A problem. In this way, if a telescope is 540 km high when pointed at the sky, it will encounter an increasingly dense network of space traffic in the form of satellites. Specifically, there are currently about 15,000 satellites in orbit, but requests to different regulators suggest that we could reach half a million satellites by the end of the 2030s. Something that would leave large space observatories unusable.
To put specific cases, we have the NASA Hubble that right now 3–4% of the images it captures have satellite trails. A figure that will increase to almost 40%, causing one in every three photographs of the most famous telescope in history to have a ‘light scar’. We have another case in SPHEREx which is the future explorer of the origins of the universe and which will have almost 100% of its catchments contaminated.
Its impact. It is undoubtedly incalculable. Missions like ARRAKIHS (of the European Space Agency, with strong Spanish participation) or SPHEREx depend on taking very wide-field images to map the structure of the universe. By having such a large field of view, the probability of dozens of satellites being “snuck in” in a single shot is 100%.
For him Chinese Xuntian Telescopewhich orbits lower, the situation is much worse. Being “below” most of the Starlink, Kuiper constellations and the Chinese networks themselves such as Guangwang You’ll have a harder time dealing with nearly a hundred bright lines crossing every image you take.
The solution. Orbiting telescopes were a solution to this problem that was occurring in terrestrial telescopes. Now history repeats itself. Experts point to the need to define precise orbits so that telescopes can avoid satellites in a simple way. But this requires great international coordination to share this information and, above all, to regulate the number of launches that are carried out.
Images | NASA Hubble Space Telescope
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