astronomers care about their observations

Many remember the first time they saw Starlink satellites. “It was 2019 and Starlink had just launched 60 satellites into orbit. They followed each other and formed a sort of train of satellites in the sky. For me, it was science fiction to see all these celestial objects in a row. It was very fast and impressive. But, very quickly, I had a second impression: the fear of seeing our sky stained with the passage of these satellites. 🇧🇷

These words, shared during an online conference, are those of Olivier Hainaut, astronomer at ESO, the European Southern Observatory in Marseille. Specializing in small celestial objects in the solar system – asteroids, comets, interstellar objects and satellites – the astronomer has published a study on the impact that the placing in orbit of new constellations of satellites by private companies will have on the observation of the sky. According to him, in 2021, about 30 constellations made up of 100,000 small satellites circling the Earth (at different altitudes) were planned.

Everybody wants their satellites

In fact, there is not only Starlink: other space telecommunications projects should be deployed in the near future, in particular those of the British company OneWeb, the Canadian company Telesat, the Americans of Amazon, Lynk and Facebook, but also the Russians of Roscosmos and the Chinese Aerospace Science and Industry Corporation. All for various telecommunication purposes, but especially for transmission over the Internet. Goal: have internet everywhere. Certainly in North America first, but also around the world. Widespread Internet access that would benefit many countries that do not yet have the necessary infrastructure for fast access, equivalent to fiber in France.

Astronomers are extremely concerned that the Earth is surrounded by tens of thousands of satellites that will far exceed the approximately 9,000 stars visible to the naked eye.

If the Starlink and consorts project makes many people and countries dream, astronomers grimace. This proliferation of new satellites is worrying. Contacted, the Grenoble Institute of Planetology and Astrophysics (IPAG) redirected the trailblazer in the words of Fabien Malbet, astrophysicist and research director at CNRS, in particular at IPAG.

“The issue of light pollution by satellites is current […] This has a huge impact on astronomers, both amateurs and professionals, as the reflection of sunlight on these satellites “illuminates” the night. Of course, we’re not talking about big lights, but just points of light that we see moving across the sky. The problem is their number. 🇧🇷

Satellites brighter than others

In fact, although satellites have been used since the 1960s – already for telecommunications – today we use 3,000 satellites. A number that rises to 19,000 if we also include those who no longer work. With ambitions of 42,000 satellites for Starlink alone, we are therefore talking about an order of magnitude greater and a much greater visual impact.

“Satellites will still have a major impact on the entire astronomical ecosystem: certain observations that require precise timing will be affected. However, it is from them that many scientific advances derive. 🇧🇷

Especially since these new celestial objects will be in much lower orbits than geostationary satellites: 340 km, 550 km and 1,150 km, compared to 36,000 km. This proximity to our atmosphere is intended to reduce the latency period between the transmission of information on Earth and its reception in space (and vice versa), but this short distance also makes them more visible and brighter in the night sky. The satellites launched by SpaceX would therefore be brighter than 99% of the population of objects visible in Earth’s orbit.

They therefore do not hide, astronomers are extremely concerned about the possibility that the Earth is surrounded by tens of thousands of satellites that will far exceed the approximately 9,000 stars visible to the naked eye. On YouTube, some videos simulate what the sky might look like when a certain number of satellites in orbit are reached.

Many scientific advances have impacted

Olivier Hainaut’s research, however, contradicts this fear, at least in part. In fact, many satellites will not always be illuminated by the Sun. That is why, according to the astronomer, the observation of the sky will be especially disturbed at dusk or in the early evening. This will be particularly the case forultra wide field image, that is, observation with telescopes with an angle of view greater than 50 degrees, whose analyzes will be greatly deteriorated in the early evening. The rest of the night must be partially preserved. But he concludes: “Satellites will still have a major impact on the entire astronomical ecosystem: certain observations that require precise timing will be affected. However, it is from them that many scientific advances derive. 🇧🇷

However, other astronomers do not necessarily share this view. Nearly 2,050 astronomers have signed a petition calling for an urgent halt to satellite launches. All signatories are listed in this online document. In their appeal, they justify their hostility to projects by Elon Musk and other companies:

“It’s not just observations with wide-field telescopes that are going to deteriorate […] but also deep/long exposures with small field installations that inevitably will be. This light pollution is extremely harmful to astronomical observations at all wavelengths. […] The degradation of scientific observations will remain significant for two reasons: 1) stars and other objects in the universe will be eclipsed, hampering studies using the time variable (variability), and, 2) the reflective ability of the surface depends on the observation wavelength, so what goes dark in one part of the spectrum (eg visible) stays bright or bright in other parts of the spectrum (eg infrared or radio). 🇧🇷

Engineers and astronomers holding hands

Aware that their word will unfortunately not stop the space and capitalist ambitions of the telecom empires behind these new constellations, astronomers are still trying to work together with the project managers and engineers tasked with designing these new satellites. The latter notably proposed the idea of ​​painting their satellites black to reduce the discomfort they might cause during astronomers’ observations. A possibility that makes space enthusiasts smile. 🇧🇷 It’s more the reflective solar panels that bother us. 🇧🇷 However, exchanges between the company and the scientific community continue.

The size of the satellites is also analyzed: according to experts contacted by the trailblazerthese satellites made of Musk, often the size of a small suitcase weighing 250 kg, will not have a lifespan of half a century, but two or three years.

“Everyone should ask themselves about the consequences of using digital technology – just as we sort our waste – on our global environment. This also goes through its impact on our starry sky. 🇧🇷

The risk of low-orbit overload is therefore on the minds of all astronomers, although they insist that the risk of collision between all these celestial objects remains minimal. There is space. “However: in the medium to long term, this will drastically diminish our view of the universe, create more space debris and deprive humanity of a pristine view of the night sky. 🇧🇷

“Does a company have the right to claim heaven?”

Some astronomers, therefore, do not hesitate to move forward and would like these projects to be much more debated in civil society. “Until now, space was a common space. The question of our ethics in this regard must be weighed in the balance: does everyone agree to sacrifice our starry skies for more online interactivity or better streaming speeds? But above all, does a country or a company have the right to claim the sky, which happens to be world heritage, common heritage? The question deserves to be asked the same way, right? 🇧🇷

As you may have understood, more generally, it is the use we want to make that raises questions, both among space enthusiasts and among civil society. If many do not deny progress for many people and countries, the climate issue encourages sobriety, including in digital uses where video reduction and other speeds are recommended.“Matching nothing, between the opponents of Starlink and 5G, the arguments overlap. 🇧🇷

The issue of antennas often comes up: for Starlink you also need terrestrial relays capable of sending the required speed. In France, three villages were contacted to host these new generation branches (Nine 2.30 m diameter parabolic balls placed on 5 m² concrete bases, editor’s note)🇧🇷 In the end, only one accepted. In Gravelines, in the north, or in Saint-Senier-de-Beuvron, between Avranches and Fougères, the mayors finally refused to give a building permit to Space X, not wanting to participate in the bidding for data for transit.

“Everyone should ask themselves about the consequences of using digital technology – just as we sort our waste – on our global environment. This also goes through its impact on our starry sky.”concludes Fabien Malbet.

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