NASA study shows that satellite light pollution can interfere with space telescopes

The exponential growth in satellites in low-Earth orbits has led to improvements in telecommunications, including broadband in rural and remote regions around the world. The increase in satellites in low-Earth orbit has also led to an explosion in light pollution, which threatens the work of orbiting astronomical observatory.

NASA's new study on four space telescopes, two of which are currently in operation and two more that are planned, estimates that many images taken by these observatories within the next decade will be affected by light emitted by or reflected from satellites orbiting low Earth.

Researchers calculated that satellite light could contaminate about 40% of the images taken by NASA Hubble Space Telescope, and 96% of the images taken by SPHEREx Observatory of U.S. Space Agency. The researchers also calculated that images taken by the European Space Agency’s planned ARRAKIHS Observatory and China’s planned Xuntian Telescope could be similarly affected.

Researchers said Hubble's narrow field of vision would make it less susceptible to damage.

Orbiting telescopes play a crucial role in space exploration. Orbiting telescopes can see a wider spectrum of electromagnetic radiation than traditional ground-based instruments. They also get clearer images because they are not affected by atmospheric disturbances.

The study, published in Nature, was led by NASA's Ames Research Center, California.

Satellites can cross in front cameras as they stare into the universe, trying to reveal distant galaxies. They leave bright traces of lights that erase the faint signal we receive from space. This problem was well-known for ground-based observatories. "Space telescopes, which are much more expensive than ground-based telescopes and located in pristine locations in space, were believed to be free from light pollution until recently," Borlaff said.

In 2019, approximately 2,000 satellites were in low-Earth-orbit. The number is now around 15,000 Borlaff stated that industry proposals foresee 560,000 satellites on low-Earth orbit within the next decade.

Borlaff stated that "to give an idea how much this number has increased recently, in the last four-year period - from 2021 to -2025 - we have launched more low-Earth-orbit satellites than in all the previous seven decades in space flight together."

Researchers used data from satellite operators, including SpaceX's Starlink and China's Guowang, to simulate orbital layers for each constellation of satellites. The researchers then looked at specific telescope properties such as orbital altitude, trajectory and field of view.

Borlaff explained that once we had our simulated telescopes watching our simulated universe we could count how many times the satellites crossed our observatories - or "photobombed" them - and measure their brightness at the time of the event.

Satellites emit and reflect multiple types of light.

They reflect the light of the Earth and the Moon, which are very bright in low-Earth orbit. Satellites emit not only optical light but also infrared radiation, which is generated by the temperature of the satellite's components. They also reflect radio waves from Earth and their antennas," Borlaff explained.

Researchers said that one solution to the problem is to place satellites in orbits lower than the ones where telescopes are located.

Some telescopes located in more distant orbits will be better protected from light pollution. The study did not examine the effects of satellites on NASA’s James Webb Space Telescope or the European Space Agency’s Euclid Observatory, nor NASA’s Nancy Grace Roman Space Telescope.

They are located much farther from Earth than telecommunication satellites.

Borlaff stated that, "for the time being, it is unlikely they will be affected by contamination of this kind."

However, these unaffected telescopes only provide a small fraction of the total number of astronomical observations.

Borlaff stated that the robots are used only for specific scientific purposes and their operational time is very limited.

(source: Reuters)