People on the ground find it difficult to observe the stars in the night sky due to light pollution from artificial light sources. Research by the National Aeronautics and Space Administration (NASA) in the United States has revealed that space telescopes are also affected by the increasing light pollution emitted or reflected by satellites, impacting astronomical images they capture.
According to a report by Agence France-Presse, NASA astronomers warned on December 3 that human plans to launch approximately 500,000 satellites into Earth’s orbit in the coming years could potentially pollute nearly all images taken by space telescopes with the light emitted or reflected by these satellites.
A study conducted by NASA scientists estimated for the first time how the large number of satellites planned for launch in the future could disrupt nearby telescopes used to explore the universe.
The study noted that since 2019, the number of satellites in low Earth orbit has surged from around 2,000 to 15,000, with many of them being part of the Starlink low-orbit satellite constellation deployed by billionaire Elon Musk.
If all currently proposed satellites are launched into orbit, the number of satellites orbiting Earth is expected to increase to 560,000 by the 2030s. NASA astronomers simulated how these satellites would impact four space telescopes.
Simulation results indicate that the light from the satellites would affect 96% of all images captured by NASA’s existing SPHEREx telescope, the ARRAKIHS telescope in the European Space Agency (ESA) program, and the Xunte telescope in Chinese plans.
While NASA’s Hubble Space Telescope is less likely to capture satellites due to its narrower field of view, about one-third of its images would still be affected.
Alejandro Borlaff, a researcher at NASA’s Ames Research Center and the lead author of the study, told Agence France-Presse that this poses a “very serious threat” to space telescopes.
Borlaff said, “Imagine you are trying to locate potentially hazardous asteroids approaching Earth.” A passing asteroid “might look just like a satellite… It’s really hard to distinguish which one is the actual threat.”
Some space telescopes remain unaffected, such as NASA’s James Webb Space Telescope, as they are positioned at a stable distance of 1.5 million kilometers (932,000 miles) from Earth at the second Lagrange point.
Therefore, they are currently less likely to be impacted by this type of pollution. However, these unaffected telescopes only contribute a small portion to overall astronomical observations.
Borlaff stated, “They are used for very specific scientific purposes, with very limited operational time.”
As for solutions to satellite light pollution, the study suggested deploying satellites at lower altitudes than space telescopes, but this might harm Earth’s ozone layer.
The most direct solution may be to reduce the number of satellite launches. However, competition from satellite network companies and the increasing demand brought by the flourishing development of artificial intelligence (AI) make this solution challenging to implement.
Borlaff noted that nearly three-quarters of the satellites in low Earth orbit belong to Musk’s Starlink network. The study predicts that with intensifying competition, Starlink is expected to represent only 10% of all satellites in the coming decades.
The research findings were published on December 3 in the journal “Nature.”