Private telecommunication companies are setting up new networks of satellites around Earth. The considerable increase in the number of satellites is worrisome. Astronomers are alarmed about the negative impact of the satellites on astronomical research. A while ago, I gave a short lecture about the problem—the video is at the bottom of this page. Here I briefly summarize the main points.

Bright satellite trails on an astronomical image. Credit: Victoria Girgis / Lowell Observatory
Swarms of telecommunication satellites
About a year ago, the Starlink company launched its first batch of sixty satellites to space. The telecommunication company, owned by technological magnate Elon Musk, will launch about 12000 satellites into space, though they announced they might increase the number to the staggering 40000. With this megalomaniac project, the company plans to provide an affordable and low-latency internet across the globe.

Starlink is not the only company with such plans. The British OneWeb has already entered the race and recently asked for permission to launch a similarly outrageous number of satellites. Naturally, Amazon will do it too. And the Chinese. And Microsoft. According to the estimates, there will be between 50000 and 100000 new satellites orbiting the Earth in the next ten years; this is more than ten to twenty times the number of all known satellites around Earth at the moment.

Unexpected light pollution of unprecedented scale

The Starlink satellites are unexpectedly bright. Many, if not most, can be seen with naked eyes at the beginning and end of the night. They don’t have their own source of light. By moving around the Earth, they get irradiated by the Sun. The sunlight reflects from their surface, and that is when we see them from Earth. Satellites in the low orbit are visible only in dusk and dawn. Those that orbit at a higher altitude are irradiated longer and can thus be seen long into the night. A bright satellite that finds itself in the field of view of a telescope during an astronomical observation leaves a bright trace on the obtained image. The exceptionally bright traces of Starlink satellites are damaging to the sensitive astronomical cameras, endangering the quality of the subsequent observations.

The issue has seriously challenged professional optical astronomy. Observatories searching for transients will be hit the hardest. Many processes in the universe—supernovae, gamma-ray bursts, merging of neutron stars—emit a lot of light in a short time. On a random part of the sky, a new source suddenly appears, just to dim and disappear in a few days. The easiest way to find transients is to search for them with telescopes and cameras with big fields of view. However, such observations are more likely to be disturbed by one or more satellites.

Several observatories, dedicated to the transient research, have been built in the past several years. Arguably the most important one will be the Vera C. Rubin Observatory. Standing in Chile, the telescope has an eight-meter primary mirror and an enormous field of view. The observatory will detect thousands of new transients every night. The satellite constellations seriously threaten the scientific potential of the observatory.

Radio and space debris concerns

Since its beginnings, the radio astronomy has been affected by the telecommunication companies, both from the ground and space. To preserve the radio sky for astronomical research, astronomers managed to protect several bands in the radio spectrum. Astronomers have an exclusive right to these bands.

Protected or not, companies, as well as governments, are known to be negligent. Too many times, radio astronomers find contamination in their bands that affects the sensitive observations. Frankly, it is not yet clear to what extent the new constellations will affect radio observations. That will be known once the satellites become operational. But if we are not vigilant, it may quickly happen that an “unfortunate mistake” deprives astronomy of precious parts of the radio spectrum.

Credit: ESA

Another concern is the sheer number of new satellites. It has been known for a long time that we are losing control over the number of satellites and space debris. The low-Earth orbit is so crowded that there exists a high probability for collisions between satellites and satellites and pieces of debris. Collisions happened before. Due to the increasing number of satellites, there is a danger that in the future, a collision would lead to a chain collision destroying many satellites (Kesseler syndrome). Such a catastrophe would render space activities difficult for a long time.

Satellite operators are paying attention to the orbits; in case of a danger of a collision, one of the satellites’ orbit is slightly changed. Such maneuvers cannot be executed indefinitely because they are demanding and use a lot of fuel. Close encounters will be more frequent in the future. Due to an increasing presence of private companies in space, a good coordination among everyone will be vital; it was worrisome to see a lousy communication between Starlink and European Space Agency last September during a close encounter of two of their satellites.

What now?
One cannot deny the importance of the development of telecommunications. But the fact is that such projects are being developed and carried out in a hurry without the necessary deliberation and long-term strategy. International regulation of space is essential, be it to prevent the light and radio contamination or to reduce the space debris.
Lecture: challenges in astronomy in the light of satellite constellations