SpaceX satellites threaten to hide asteroids that pose danger to humanity

The International Astronomical Union demands that urgent action be taken against the uncontrolled proliferation of these devices. Satellite constellations make it difficult to search for objects at risk of impacting the Earth

The world experienced an unusual asteroid impact on January 21, with pieces of a meteorite falling near Berlin. The extraordinary thing was that, at 1:32 a.m. local time, there were already hundreds of people waiting for the arrival of 2024 BX1 (the name given to the object).

According to photos and video testimonies posted on social media that Sunday morning, some of these spectators knew exactly where they had to look. An hour and a half before the asteroid hit the Earth, NASA had issued a warning that anticipated when, how and where exactly the impact was going to occur. A space rock was heading at full speed towards the outskirts of the German capital. There was an expectation that it would leave a spectacular trail in its wake as it disintegrated upon entering the atmosphere.

Three hours before impact, asteroid 2024 BX1 was completely unknown to science. The Hungarian astronomer Krisztián Sárneczky was the first person to observe it. He quickly sent an alert to the Minor Planet Center. Subsequently, the official body made its data available to the international astronomical community. New confirmations soon arrived from observatories throughout Europe. Just 70 minutes after the discovery, NASA’s Scout system confirmed that the probability of impact with Earth was 100%. And, less than 30 minutes after that, new data made it possible to specify the trajectory and size of the asteroid, which was barely three feet wide. It was harmless.

This celestial encounter with a double happy ending — both due to the absence of damage and the success in early detection and rapid response — has been a milestone for scientists working on Earth’s planetary defense systems. But their efforts clash with Elon Musk’s plans to add tens of thousands of satellites in the coming years to the Starlink network — operated by his company SpaceX — to provide global broadband internet coverage. Astronomers aren’t hiding their concern.

The International Astronomical Union’s experts centre has just published its first report on artificial satellite constellations, such as those operated by SpaceX, OneWeb and Amazon. The document, which compiles all the scientific evidence on this subject to date, urges the global community to take measures against the current uncontrolled proliferation of satellites. It confirms that, among other negative effects for the field of astronomy, these devices threaten the ability to detect asteroids and comets that pass near our planet (so-called “near-Earth objects,” or NEOs).

From his observation post at the Piszkéstető Astronomical Station, located on a mountain northeast of Budapest, Krisztián Sárneczky says: “The trend is very worrying. When I started my intensive NEO search with this telescope four years ago, satellites rarely crossed the field of view. But today, I don’t have a single image that doesn’t have at least one.”

Detecting an asteroid before it hits the Earth is exceptional. It has only been done eight times so far in history. In three of those eight instances, the goal was scored by Sárneczky, who warns EL PAÍS of the consequences that this boom in new satellites will bring. “If the expansion continues at this rate, we’ll soon miss an approaching celestial body because a satellite passes right in front of it in one or more of the images.” In 2020, the Starlink fleet didn’t number 800 devices. Today, however, there are over 6,000, while Musk plans to reach 42,000 in the coming years.

This forecast coincides with that of Siegfried Eggl, a researcher at the University of Illinois. He studies NEOs and the impact of satellite megaconstellations: “At the moment, the impact of satellites on planetary defense is negligible. However, based on the recent increase in the rate of launches, as well as the current filings with the FCC (the U.S. Federal Communications Commission) for hundreds of thousands of satellites in Low Earth Orbit, that can soon change… especially if appropriate brightness-mitigation strategies aren’t widely adopted.”

NEO hunters such as Sárneczky and Eggl pay special attention to twilight, which is when the most elusive asteroids can be detected. These are the ones with trajectories of the Apollo and Aton types, which intersect with that of the Earth. And as they come from the inner solar system, from our cosmic point of view, they’ll always appear in the sky close to the Sun. This is similar to the inner planets — Mercury and Venus — which can only be seen in the hours after sunset and before sunrise, always at medium and low altitudes. In the middle of the night, they remain hidden beneath the horizon.

These detection difficulties make asteroids of this type especially dangerous, when they measure several dozens of feet wide, such as the one that hit Chelyabinsk, Russia, back in 2013. It exploded 18 miles above the ground, releasing 30 times more energy than the atomic bomb in Hiroshima. On the surface, the shock waves caused extensive damage and injuries. Current planetary defense systems aspire to be able to detect such asteroids, so that the authorities can be notified in case the impact could cause damage in populated areas. And satellites like the ones manufactured by Starlink pose an added difficulty to accomplishing this. These artificial and mobile stars shine brightly, especially at the same times and in the same areas that astronomers pick to go out to hunt for dangerous NEOs.

“In general, it’s true that astronomical observations will contain many more satellite streaks during twilight. This is the time when satellites reflect most of the sunlight back to Earth, because they’re not in Earth’s shadow yet,” Eggl explains.

Eggl leads the working group on the solar system within the Legacy Survey of Space and Time (LSST), a project established to carry out the most complete census of the sky in history, over the course of 10 years. The work takes place from the Vera C. Rubin Observatory, which is currently under construction in northern Chile, with an expected opening date set for the end of 2025. According to Eggl, the new large American telescope at the site will become “the dominant contributor to discovering near-Earth asteroids in the coming years,” although it will surely “be affected” by the proliferation of satellites.

“It’s difficult to say exactly how many asteroids will be lost… but preliminary results suggest that for every five near-Earth asteroids we discover, we lose one solely due to constellation interference. That’s if no mitigation measures are taken,” Eggl notes.

From the University of Washington, Meredith Rawls is working on preparing the Vera C. Rubin Observatory’s software. This will allow the observatory to operate with this upcoming sky full of artificial stars… something that wasn’t anticipated when the project was presented. The researcher explains that the new telescope “is designed to have a wide field of view, collect a lot of light and take new images of the whole southern sky every few nights. These features will enable it to achieve our key scientific goals, which range from studying objects in our solar system to better understanding the fate of the universe. However, these same features make it uniquely vulnerable to large numbers of bright satellites.”

A big astronomical project compromised

If the plans laid out by SpaceX and other operators come to fruition, the 10 years of the LSST project will coincide with a major explosion in the number of satellites in orbit. Therefore, Rawls’ team is testing and refining an algorithm to identify satellite traces and “distinguish them from signals that are useful for science, marking each contaminated pixel within an astronomical image. The challenge is to do this accurately and quickly.”

When it comes to determining if a light corresponds to an asteroid that can impact or graze the Earth in a matter of hours, or if it’s simply light pollution from satellites, time is precious.

The other measure proposed by the Vera C. Rubin Observatory to counteract this problem is to repeat the scan of the lower part of the sky during the hours of twilight. But, according to Eggl, in addition to taking too long, this method takes time and resources away from other tasks: “[Scanning] the same spots on the sky more often to reduce the impact of satellites every night negatively affects our ability to spot supernovae and other transients… it can hurt cosmological research.”

The International Astronomical Union (IAU), a Brussels-based NGO with nearly 90 member states, has opted to collaborate with SpaceX, which manages more than half of all the satellites now in orbit, and other operators, so as to develop measures that mitigate the impact of satellites. Reducing the brightness of these objects isn’t an easy task. Additionally, it defies common sense: moving them to a further low-Earth orbit makes them less bright, but it worsens the problem.

Spanish astrophysicist David Galadí, a researcher at the University of Córdoba who studies this problem, explains that “if the satellites orbit a little higher, they go more slowly, meaning that they pass over the telescopes for longer, damaging their astronomical images even more.” For this reason, in the recently-published report, experts from the IAU demand that the satellites have a maximum brightness of magnitude 7… so weak that it cannot be seen with the naked eye. This applies to satellites that orbit 342 miles above the Earth, like the ones produced by Starlink. However, the document warns that for satellites that fly higher — like those from OneWeb — the brightness must be even lower.

All experts consulted by EL PAÍS warn that no operator has managed to get under this brightness limit. Through its program in collaboration with astronomers, SpaceX has tested several ideas without success. The first attempt was to paint a satellite a dark color, which reduced its brightness (although not by enough) and caused it to overheat. Later, the firm tried attaching a sunshade to reduce reflection but this diminished the satellite’s brightness by an even more negligible amount.

In the second generation of its satellites — the Starlink v2 Mini — Elon Musk’s space company is now combining several mitigation techniques. These include everything from a new blackout paint, to covering the part of the satellite that faces Earth with mirrors that deflect light in other directions, while avoiding direct reflection. But SpaceX admits that it hasn’t tested these solutions enough to guarantee that they’ll work. And these new satellites — which, despite their name, are larger than the first generation ones and have more surface area to reflect light — have still been in circulation for too short a time for the astronomical community to have been able to publish complete analyses of their impact.

Meanwhile, SpaceX is already preparing the launch of a fleet of full-size Starlink v2s. These satellites, which are even larger than the previous ones mentioned, are designed to provide a 5G connection from space directly to mobile phones (the current ones communicate with satellite dishes installed in users’ buildings). The company AST SpaceMobile works along the same lines: it chooses to use fewer satellites than SpaceX, albeit much larger ones. Its prototype, BlueWalker 3, increased astronomers’ concern about megaconstellations when a 2023 study determined that this artificial star had become one of the brightest objects in the entire sky. Its apparent magnitude — 437 times brighter than recommended — means that it can ruin an entire astronomical image, rather than just contaminating a few points.

However, it’s not only the sunlight reflected by these satellites that poses a problem for science. IAU experts warn that, at all hours, the radio waves that the devices use to bring the internet to any point on the planet interfere with the observations of radio telescopes. “Radio astronomy — fundamental to understanding the formation and evolution of stars and the universe — has no way of escaping from satellite megaconstellations,” Galadí explains.

In its report, the IAU offers advice to member states and satellite operators, calling for decisive investment to develop new technologies that mitigate the impact of satellites. It also asks the aforementioned space companies to share detailed data regarding their trajectory in real time, so that astronomers can know when they’re going to appear and successfully avoid them.

The risk of saturating low-Earth orbit

Other astronomers, however, have decided to move on to confrontation. For instance, the nonprofit DarkSky International has gone to court to appeal the FCC’s decision to grant licences to SpaceX to deploy its second-generation Starlink satellites. The group claims that the FCC granted these licenses to the firm without a proper assessment of their impact. Alejandro Sánchez, an astrophysicist at the Complutense University of Madrid, who is part of DarkSky, explains that “there’s already a clear international regulation to apply in these cases: it’s the 1979 Geneva Convention on Long-Range Transboundary Air Pollution.”

Sánchez says that we’re facing a gigantic experiment that hasn’t been planned. He also points out that the environmental risks from a multitude of satellites re-entering the atmosphere on an annual basis haven’t been evaluated. These devices have a useful life of several years, and they eventually disintegrate, dispersing components such as aluminum whose adverse effects haven’t been studied. On the other hand, this researcher affirms that “around February 14 of each year, there’s an excess of large bolides, like the one in Chelyabinsk. But megaconstellations compromise the scientific research required to detect the dangerous asteroids that cause them: we still don’t know their origin.”

Galadí points to another risk of satellite proliferation: collisions, which have already happened on several occasions. These increase the amount of space debris, turning low-Earth orbit into an increasingly difficult and risky place to operate. This astronomer — who compares the current situation with that of the Wild West — believes that the pioneers of this new territory (such as the current dominant firm, SpaceX) should be the first parties interested in regulating the use of these satellites: “In a lawless space, they’ll never be able to develop their multibillion-dollar business with sufficient safety guarantees.”

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