By BlueShift | 2025-12-24

Light pollution produced on Earth diminishes visibility from ground-based observatories, with scientists now warning that space telescopes are at risk from the light produced in space by surging fleets of satellites.

Rapidly growing satellite constellations, fueled by lower costs and increasing demand for communication, navigation, Earth observation and scientific research, have raised strong concerns among the scientific community.

But a study published December 3 in the Nature journal, authored by three NASA-affiliated scientists, is the first to estimate how the immense number of satellites planned for the future could stray into the view of nearby telescopes.

By the end of the 2030s, the study warns, the light from these satellites could contaminate almost all the images taken by space telescopes.

"Reflections from satellites can be visible to the unaided eye and extremely bright for professional telescopes," the study's abstract says.

"These trails already affect astronomical images across the complete electromagnetic spectrum, with a noticeable cost for operations and mitigation efforts."

"Contrary to popular perception, satellite trails affect not only ground-based observatories but also space observatories such as the Hubble Space Telescope."

"However, the current number of satellites is only a fraction (less than 3%) of those to be launched in the next decade."

Since 2019, the number of satellites in low-Earth orbit has skyrocketed from roughly 2,000 to 15,000, according to the study.

If all of the plans currently filed to regulators launch into space, there will be 560,000 satellites orbiting Earth by the end of the 2030s.

This poses "a very severe threat" to space telescopes, the study's lead author, Alejandro Borlaff of the NASA Ames Research Center in California, told AFP.

Tainted by reflected light

For the research, the astronomers simulated how 560,000 satellites would impact four space telescopes.

Reflected light from the satellites would affect 96% of all images taken by NASA's SPHEREx telescope, the European Space Agency's planned ARRAKIHS telescope and China's planned Xuntian telescope, the study found.

The Hubble Space Telescope, which is less likely to snap a satellite as it takes in a narrower view of the universe, would have a third of its images tainted.

This could have an impact on all sorts of scientific endeavors.

"Imagine that you are trying to find asteroids that may be potentially harmful for Earth," Borlaff said.

An asteroid streaking through the sky "looks exactly like a satellite... it's really hard to figure out which one is the bad one," he added.

Some space telescopes, such as NASA's James Webb Space Telescope, are unaffected because they are hovering at a stable spot 1.5 million km from Earth called the second Lagrange point.

'As bright as a planet'

One solution could be to deploy satellites at lower altitudes than space telescopes -- but that could potentially deplete Earth's ozone layer, the study said.

The most straightforward solution may just be to launch fewer satellites.

But competition from rival satellite internet companies -- and the surging needs of the artificial intelligence boom -- make that unlikely.

Nearly three-quarters of the satellites currently in orbit are part of the Starlink network, Borlaff said.

But Starlink is expected to represent just 10% of all satellites within a few decades as competition blasts off, according to the study.

For now, companies could help by providing the location, orientation and color of their satellites to those operating space telescopes, Borlaff said.

Another problem is that satellites are getting much bigger.

To the naked eye, satellites that are 100 square meters in size are "as bright as the brightest star that you can see in the sky," Borlaff said.

However, to handle AI's data requirements, there are now plans to build ones 3,000 square meters wide.

These giants could be "as bright as a planet," Borlaff added.