Space-based astronomy, once considered free from the disturbances caused by urban light or atmospheric interference, is now confronting a surprising and rapidly growing threat. A NASA-led study has revealed that the surge in low-Earth orbit (LEO) satellites is increasingly contaminating images captured by space telescopes, including some of the world’s most important scientific instruments. The findings indicate that reflected sunlight, emitted infrared radiation and radio signals from thousands of satellites are degrading the quality of astronomical observations.

Space telescopes face unexpected “light pollution”

Traditionally, the challenge of light pollution has been associated with ground-based observatories, where artificial lighting and human activity obscure faint cosmic signals. However, the study finds that space telescopes — previously insulated from such interference — are now vulnerable as LEO satellites pass through their line of sight.

These satellites create bright streaks across images, overpowering weak astronomical signals. They not only reflect sunlight, moonlight and Earth-shine but also emit heat-based infrared radiation from onboard components and reflect radio wavelengths used in communication.

According to NASA researchers, these effects are strong enough to compromise the scientific output of telescopes previously regarded as unaffected by human-made environmental factors.

Up to 40% of Hubble images may be impacted

The NASA-led investigation examined four major observatories — two already operational and two upcoming missions — and found “concerning” levels of contamination.

Key findings include:

  • Around 40% of images from the iconic Hubble Space Telescope may be affected by satellite interference.
  • The forthcoming SPHEREx mission could face contamination in up to 96% of its images.
  • The European Space Agency’s ARRAKIHS mission and China’s planned Xuntian telescope are also projected to see high levels of interference.

These numbers underscore the magnitude of the problem, especially as astronomy increasingly depends on long-duration, faint-signal observations to explore dark matter, galaxy formation and early cosmic evolution.

The root cause: An exploding satellite population

The growing interference is closely tied to the exponential rise in satellite launches, driven primarily by global efforts to expand internet access and communication networks.

  • In 2019, there were roughly 2,000 satellites in LEO.
  • Today, that number has surged to nearly 15,000.
  • Scientists warn that the total could reach 560,000 satellites within the next decade.

Such “sky crowding” significantly increases the chances of satellites crossing the field of view of space telescopes many times per day.

Researchers caution that the long-term implications could be serious: reduced image clarity, greater data loss and the need for more complex correction algorithms, which may not fully restore the original astronomical signals.

Mitigation: Launching satellites at lower orbits

To address the growing threat, scientists recommend designing and launching future satellites into lower orbits than major observatories. Telescopes observing from higher altitudes would then be less prone to interruptions.

Fortunately, some of the most ambitious observatories — including NASA’s James Webb Space Telescope (JWST) — orbit far beyond LEO, at a distance of 1.5 million kilometres from Earth, making them immune to this particular issue.
However, many future missions intended to operate closer to Earth may face substantial challenges unless satellite regulations evolve.

Implications for India and global scientific progress

For India, where space science and astronomy are rapidly advancing through missions led by ISRO and academic institutions, the findings highlight the need for early policy engagement. India is developing its own satellite constellations and planning next-generation telescopes; experts suggest that balancing communication needs with astronomical integrity will be essential.

Karnataka, home to major space research hubs in Bengaluru such as ISRO headquarters, the U R Rao Satellite Centre and several astrophysics institutions, will have a particularly significant role in shaping national strategy around satellite deployment and scientific observation.

Researchers emphasise that the issue is not a call to halt satellite launches but to ensure responsible and coordinated planning. Without mitigation, the cumulative effect of satellite interference could limit humanity’s ability to study distant galaxies, star formation processes and exoplanet atmospheres — key goals for many upcoming missions.