Sunlight-Reflecting Satellites Spark Concern Among Astronomers

Plans to use satellites capable of reflecting sunlight to the Earth’s surface have become a concern among astronomers.

The technology is being developed to harness sunlight after sunset, but at the same time raises concerns about its impact on the night sky and astronomical observation activities.

One project drawing attention is Reflect Orbital, a company developing satellite technology with reflectors or mirrors in space.

In a filing with the Federal Communications Commission (FCC), the company proposed operating the Earendil-1 satellite to test space reflector technology designed to bounce sunlight to specific locations on Earth’s surface. The satellite is planned to operate in an orbit approximately 625 kilometres above Earth.

This technology essentially serves a different purpose from ordinary communications satellites.

The reflector is designed to direct sunlight to specific areas so that the Earth’s surface remains illuminated even after the Sun has dipped below the horizon.

The concept could potentially be used to support solar power plants as well as certain lighting needs.

However, the ability to reflect light from orbit is precisely what poses a problem for astronomers. Sunlight reflected by objects in low Earth orbit can enter the field of view of telescopes and produce bright streaks in astronomical images. This can interfere with observations of very faint celestial objects.

The European Southern Observatory (ESO) has even modelled the impact if Reflect Orbital were to develop a constellation of up to 50,000 reflecting satellites. Simulation results show that light reflected and then scattered by the atmosphere could make the sky around the Very Large Telescope (VLT) three to four times brighter.

Astronomers’ concerns are not limited to sunlight-reflecting satellite projects. The growth in the number of satellites in low Earth orbit in general has become a concern for the astronomy community.

Research published in Nature shows that light reflected from satellites can produce bright streaks in astronomical images and potentially disrupt telescopes on Earth as well as telescopes in space.

If the number of satellites continues to grow, the problem could become increasingly complex. Reflected light does not always have to be aimed directly at a telescope to cause interference.

Light scattered by the atmosphere can also increase the brightness of the sky background, making faint astronomical objects more difficult to observe.

Even so, light-reflecting satellite technology is still in the development and testing phase. The main issue is not simply whether the technology can work, but how its use can proceed without sacrificing the interests of astronomical research.

For this reason, astronomers and relevant institutions are urging mitigation measures, such as controlling satellite reflectivity levels, regulating satellite orientation, providing accurate orbital data, and coordinating with the astronomy community.

Such efforts are needed so that the development of the space industry can continue alongside efforts to preserve dark night skies for scientific research.