In just a few years, the megaconstellations of satellites They have gone from being the great promise of global telecommunications to becoming a serious concern for astronomy. What was once a largely technical debate has transformed into a clear warning from the scientific community: if action is not taken in time, satellites could end up being more visible than the stars themselves in scientific images.
A new work published in the journal Nature It has clearly defined a problem that many astronomers had been denouncing in a piecemeal fashion. The study concludes that the low Earth orbitssaturated with communications and observation satellites, can seriously compromise the usefulness of space telescopes, including some key projects in which Europe participates and which Spain partly coordinates.
A sky full of satellites: from 2.000 to hundreds of thousands
The International Astronomical Union already warned a few years ago that a time would come when Satellite trails would be more abundant than stars in many observations. What then sounded like a long-term warning is beginning to materialize much sooner than expected due to the rate at which the fleet of spacecraft in orbit is growing.
In 2019 it was estimated that there were around 2.000 satellites operational around the Earth. Today the figures range between 12.000 and 15.000 units, a leap driven by the reduction of launch costs and due to very lax international regulation, which has facilitated the expansion of private projects such as Starlink (SpaceX), OneWeb or other national and commercial systems.
The most recent projections are, to say the least, alarming. According to databases of planned releases and estimates used in the study, by mid-century there could be up to 560.000 satellites in low Earth orbit, at altitudes ranging from approximately 160 to 2.000 kilometers. The European Space Agency (ESA) is also considering scenarios with more than 100.000 spacecraft by the 2030s.
This exponential growth turns low Earth orbit into a kind of highway saturated with artificial objectswhere not only does the risk of collisions and space debris increase, but also the light impact on telescopes that need the cleanest possible sky to carry out cutting-edge science.
The new study: Hubble, SPHEREx, ARRAKIHS and Xuntian in the spotlight
The work led by Alejandro Borlaff, a researcher at NASAThis study systematically analyzes, for the first time, the impact of these megaconstellations on four specific space telescopes. Two are already operating in space—the veteran Hubble and the future SPHEREx, both from the US agency—and two others correspond to missions from China (Xuntian) and the ESA: the project ARRAKIHS, scientifically coordinated from Spain.
To quantify the problem, the team has used detailed simulations These models replicate the evolution of the low-Earth orbit satellite population from around 2019 to the scenarios projected for the coming decades. Using publicly available constellation profiles and tools such as the Skyfield astronomical calculation modules, they have modeled how the images obtained by each telescope would look as the number of satellites increases.
This is not an isolated first approach. satellite pollution in the ground-based astronomy It is well documented, and the same is true of the traces that already appear in many images from current space telescopes. The difference is that, until now, there was no... global and quantitative vision of the problem applied to space observatories that share altitude with megaconstellations.
The results, according to several experts consulted, are hardly reassuring. The study concludes that, if the deployment plans announced by the industry are fulfilled, the benchmark space telescopes They will see a huge part of their observations contaminated., with scientific consequences that are difficult to accept.
Up to 96% of images affected and loss of scientific data
The figures presented in the study are compelling. In the case of hubble space telescopeIt is estimated that in the future, around 39% of its images will contain at least one satellite track, with an average of slightly more than two devices per exposure (2,14). This implies that a significant fraction of the data will be partially or totally unusable for certain studies.
The situation is even more serious for the other three telescopes analyzed. SPHEREx, ARRAKIHS and XuntianThe model indicates that up to 96% of its images could show satellite tracks. In terms of the average number of devices per image, the simulations suggest approximately 5,6 visible tracks for SPHEREx, almost 70 satellites per image in ARRAKIHS and around 90 in the case of Xuntian, figures that illustrate the level of saturation of the orbital environment where they will operate.
The authors emphasize that space telescopes depend on long exposures and extreme contrast To detect very faint objects, such as distant galaxies, dark matter, or fine structures in the vicinity of exoplanets. When a bright streak crosses the field of view, it can completely ruin the scientific value of the image, especially in observing programs that require combining many shots of exquisite quality.
Several researchers also point out that the study's estimates could even be conservative. Alejandro Sánchez de Miguel, from the Institute of Astrophysics of Andalusia (IAA-CSIC), notes that There are constellations and private projects that haven't even been considered because of the difficulty of keeping up with all the initiatives that are emerging, so the real impact could be greater.
Visible brightness even without direct sunlight
The work is not limited to counting the number of satellites, but also analyzes in detail the brightness of the tracesTo achieve this, the spectral energy distribution was simulated by combining several sources: the reflected light from the Sun and the Moon, the Earth's albedo, and the thermal infrared emission originating from the electronic components of the satellites themselves.
The findings show that a very significant fraction of these devices turn out detectable even when not directly illuminated by the sunIn the infrared, where some of these telescopes operate, thermal emissions make many tracks especially bright, further complicating the task of cleaning the images.
This means that simply scheduling observations at specific times of night or in specific geometries to avoid satellite glare is not enough. The problem becomes practically omnipresent in certain bands of the spectrum and in regions of the sky heavily congested by the orbital paths of the megaconstellations.
The combination of an increasing density of instruments, significant brightness at various wavelengths, and the matching of altitudes with telescopes results in a potential massive data loss, both in quantity and quality, with a direct impact on cutting-edge research areas.
Spain and Europe: ARRAKIHS and science at stake
One of the points that most concerns the European scientific community is the effect on ARRAKIHS, an ESA telescope whose scientific coordination is based in Spain. This mission is designed to study very faint structures in the halos of nearby galaxies and provide clues about the dark matter, for which it needs extremely clean and deep images.
According to the simulations, ARRAKIHS could find itself in a scenario where virtually all of his observations They contain light trails from satellites, with dozens of devices crossing each exposure. For a project designed to capture minute signals, this level of interference represents an enormous challenge that could compromise some of its scientific goals.
From the Spanish research centers involved, such as the Institute of Astrophysics of the Canary Islands (IAC) and the IAA-CSIC, it is emphasized that high-impact European science Its performance could be seriously compromised if the regulation of the orbital environment is not taken seriously. ARRAKIHS is not an isolated case: other ESA space telescopes, both current and future, will face similar problems if orbits continue to fill up at the projected rate.
Olga Zamora, an astronomer at the IAC, defines the results of the study as "devastating" and "alarming"It also recalls Elon Musk's past statements, when he argued that simply placing telescopes in space would be enough to escape Earth's light pollution. The new scenario demonstrates that this solution no longer works: Pollution also reaches space observatories, which operate in the same environment as megaconstellations.
For Zamora, the situation is clear: if the mass deployment plans are maintained, «The science of the future is at stake."Postponing decisions or relying entirely on partial technological solutions could leave an entire generation of instruments working in conditions far below what their designs allow."
The voice of the experts: from pollution to cultural heritage
The scientific community's concern goes far beyond technical inconvenience. Researchers like Alejandro Sánchez de Miguel describe the massive deployment of satellites as a kind of "uncontrolled geoengineering experiment", in which the environment near Earth is being modified without a comprehensive assessment of its consequences.
This impact is not limited to professional astronomy either. Researcher Jorge Hernandez Bernal, from the CNRS and the Sorbonne University, emphasizes that megaconstellations They degrade the cultural heritage represented by the night sky.Stargazing is a central element in numerous cultures around the world. Some traditions, even those recognized as intangible cultural heritage, require stargazing to be passed down from generation to generation.
Hernández Bernal also warns of other risks associated with increased orbital density: the possibility of triggering a Kessler syndrome—a cascade of collisions that generates even more space debris—, the increase in launches with their associated emissions, or the impact of the disintegration of orbital debris on the Earth's atmosphere.
For many specialists, this problem is too similar to other global challenges: there is a socioeconomic system that drives continuous growth, strong competition between megacorporations and states, and an absence of governance mechanisms capable of imposing clear and equitable limits on the use of space.
Partial solutions and the need for international regulation
The study published in Nature also explores possible avenues for mitigate the impact of megaconstellations on space telescopes. One of the proposals that has been put forward involves deploying the satellites in lower orbits than those of scientific observatories, so that their traces do not cross the fields of vision as frequently.
However, this strategy has a catch. Operating at lower altitudes can involve more atmospheric re-entrieswith emissions and waste that could affect the ozone layer, in addition to requiring more fuel to maintain their orbits. Several experts consider these types of measures to be, at best, "Patches" that do not address the root of the problem: the total number of satellites and the model for exploiting the space environment.
Institutions such as the IAA-CSIC are insistently calling for action to begin apply existing space legislation and that international agreements be strengthened to limit uncontrolled deployment. The idea is that near-Earth space be managed as a common resourceand not as a territory where the law of the first to arrive and launch the fastest prevails.
Hernández Bernal argues that the only realistic solution lies in a effective democratization of spacewhere decisions about what is launched, how many satellites, and for what purposes are made multilaterally, transparently, and with the participation of civil society. Otherwise, he warns, there is a risk that a few companies and powers will effectively dictate the future of sky observation for all of humanity.
Meanwhile, astronomers insist on the urgency of to put a stop to the current pace of releasesThe almost exponential growth of megaconstellations leaves less and less room for reaction: the more populated the low orbit is, the more difficult it is to correct course without incurring enormous costs, both economic and scientific.
The new study and the experts' assessments paint a picture in which the megaconstellations of satellites They threaten to profoundly alter the ability of space telescopes to explore the universe. Without decisive action, humanity could see some of its most ambitious instruments operating in a sky scarred with light, wasting crucial observations and jeopardizing a scientific and cultural heritage that has taken centuries to build.
