Protect our skies campaign

The project Protect Our Skies wishes to raise awareness about the detrimental effects of satellite constellations on ground-based astronomy. With simple yet suggestive posters we wish to draw attention to the problem. “Trash” as a common theme combines the sentiment that satellites pollute the night sky and the fact that the increasing number of satellites are bound to aggravate the problem of space debris in the low Earth orbit.

Scroll down to read more about the constellations and their effect on the night sky or use an interactive infographic explaining the problem.

Feel free to use, distribute, and print the posters to spread the word. Posters of higher resolution can be downloaded here. We also translated posters in several languages (we are happy to provide translations in other languages upon request): Spanish, Ukrainian, Dutch, Slovenian (see Slovenian webpage).

Team: Kateryna Frantseva (@frantseva_k, homepage), Martha Irene Saladino (@mairensaro, homepage), Jure Japelj (@JureJapelj, homepage)

Astronomy and bright satellites: Interactive infographic (click on the hand, mobile users should rotate their screens)
Astronomy and bright satellites: In words

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. Here we briefly summarize the main points.

Bright satellite trails on an astronomical image. Credit: Victoria Girgis / Lowell Observatory
Swarms of telecommunication satellites

About two years ago, the Starlink company launched its first batch of sixty satellites to space. The telecommunication company will launch about 12000 satellites into space, though they announced they might increase the number to the staggering 40000. With this large-scale 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. Naturally, Amazon will do it too. And the Chinese. And Europe. By the time you’re reading this, probably many more. 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 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. Furthermore, because it is so difficult to remove the traces from images, sensitive observations of faint galaxies will also take a blow (see the SATCON1 report for a full list of impacted science cases).

Several observatories, dedicated to the transient research, have been built in the past several years. The Vera C. Rubin Observatory will be one of them. 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. It will also observe millions of faint galaxies. 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 fully 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 in September 2019 during a close encounter of two of their satellites.

What now?

Astronomers have been complacent before Starlink started launching swarms of satellites. To mitigate the detrimental effects of the satellites, and to prevent further damage, the community has organized several workshops, conferences, and meetings. The next important meeting will be SATCON2.

What can we all do? We can learn about the problem and discuss it with others. The more we talk about it, the more of us there are who care about the sustainability of space, the more likely it is that we will be heard by the right people, organizations, and actors with the power to make a change.

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. Let’s change that!

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