Satellite Surge Threatens Clarity of Space Telescope Observations
The rapid expansion of satellites in low-Earth orbit is driving major advances in global telecommunications, bringing broadband connectivity to remote regions. Yet this same growth has intensified light pollution in space, posing a growing threat to the work of orbiting astronomical observatories.
Rising Satellite Numbers Cloud Astronomical Data
A NASA-led study has revealed that light reflected or emitted by satellites could compromise a significant proportion of images captured by four major space telescopes—two currently operating and two still in development. The analysis found that about 40% of images taken by NASA’s Hubble Space Telescope and nearly 96% of those from the upcoming SPHEREx mission may be contaminated by satellite light. Similar contamination rates are expected for the European Space Agency’s ARRAKIHS observatory and China’s planned Xuntian telescope.
Researchers noted that Hubble’s narrow field of view offers some protection, reducing its vulnerability compared with wider-field instruments. However, the growing density of satellites in orbit makes interference increasingly difficult to avoid.
Space Telescopes Face a New Kind of Pollution
Space-based observatories play a vital role in modern astronomy. Operating above Earth’s atmosphere, they can capture clearer and more detailed images across a wider range of the electromagnetic spectrum than ground-based telescopes. This capability allows them to study distant galaxies and even detect planets beyond the solar system.
“Until now, light pollution mainly came from cities and vehicles,” said lead researcher Alejandro Borlaff of NASA’s Ames Research Center in California. “But the rise of telecommunication satellite constellations is rapidly affecting astronomical observatories worldwide.”
Borlaff explained that as telescopes observe the universe, satellites can pass in front of their cameras, leaving bright streaks that obscure faint cosmic signals. While such interference was once a problem mainly for ground-based telescopes, it now threatens instruments in space that were previously considered immune to human-made light pollution.
Surging Satellite Constellations
In 2019, around 2,000 satellites orbited Earth. That figure has since soared to about 15,000, with industry projections suggesting as many as 560,000 could be launched within the next decade. “We have launched more satellites in the past four years than in the previous seven decades of space flight combined,” Borlaff said.
The team simulated satellite constellations from major operators including SpaceX’s Starlink, China’s Guowang, and Amazon’s planned Project Kuiper. They modelled telescope observations based on altitude, trajectory, and field of view, then calculated how often satellites would cross telescope sightlines and how bright they would appear.
Satellites not only reflect sunlight from their panels but also bounce light from the Moon and Earth. They emit infrared radiation due to their temperature and reflect radio wavelengths, adding further interference.
Possible Mitigation and Outlook
One proposed solution involves placing satellites at lower altitudes than the telescopes themselves. The study did not examine telescopes such as NASA’s James Webb Space Telescope, the European Space Agency’s Euclid mission, or NASA’s upcoming Nancy Grace Roman Space Telescope, as their more distant orbits largely protect them from satellite light pollution.
However, Borlaff cautioned that these far-flung observatories conduct only a fraction of all astronomical observations and are reserved for highly specific missions. “They have very limited operational time,” he said, noting that the challenge for near-Earth observatories will likely grow as more satellites are launched.
with inputs from Reuters