Rachel Street still remembers what fear she recently came over after a planning meeting for Vera C. Rubin Observatory. The new flagship telescope, which is currently being built in Chile, should in future take pictures of the entire sky with a performance that is sufficient to recognize a golf ball in the distance of the moon. The main project of the large telescope, the "Legacy Survey of Space and Time" (LSS), will map the galaxy, inventorize objects in the solar system and explore mysterious flashes, blinds and rashes throughout the universe. But its goals may never achieve if the sky continues to fill up with false stars. New satellite swarms, such as SpaceX ’Starlink, threaten to put those real sky objects in the shade that arouse the interest of the astronomers - and that have always admired and explored people.
"The more conferences I attend where we explain the effects of satellites, the more afraid I am about what happens to astronomy," says Street, an astronomer at Las Cumbres Observatory. When one of the scientists also present at the meeting talked about bringing certain observations forward on schedule, Street had a grim premonition: it may soon be too late for some planned sky surveys. "It sent shivers down my spine," she recalls.
Since the near -earth orbit is increasingly filling with satellite constellations for telecommunications, astronomers have to check how to continue their work when blinking solar panels and radio signals excrete the real cosmic objects. The latest reports from the planning staff of the Rubin Observatory and the US Court of Auditors, the Government Accountability Office (GAO), draw a dark picture according to which astronomy-one of the first sciences-appears directly threatened. It is feared that the satellite constellations, if they increase uncontrollably, not only endanger the future of the ruby observatory (both its general potential for discoveries and its physical components), but almost every project to observe the universe in the visible spectrum of light.
"Depending on how many satellites will be put into operation in the coming years and how bright they are, it looks very bad to catastrophic," says Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who researches satellites. "A few thousand satellites are a nuisance, but hundreds of thousands are an existential threat to ground-based astronomy".
The project managers of the telescopes are forced to adjust their plans in order to avoid the new satellite swarms. However, this already difficult task will become impossible in the next few years, as the number of space objects in low-Earth orbit will increase dramatically. Some astronomers are already trying to develop software that can calculate bright satellite streaks from their images. But even this will be in vain if the latest satellites make it into orbit; they are so bright that they endanger the basic electronics of the telescope cameras. Scientists studying such diverse phenomena as colliding black holes and near–Earth asteroids worry that they will miss exciting discoveries - but also cosmic threats. The choice of words is becoming increasingly drastic: it is "probably high time for the alarm bells to ring. I would even say almost too late, " says Anthony Tyson, an astronomer at the University of California and senior scientist at the Rubin Observatory.
Around 5400 satellites currently circle the earth
Since the launch of Sputnik 1 in October 1957, the Earth has been swarmed by artificial satellites. About 5400 of them are currently orbiting the Earth, with more than half of them owned by U.S. companies or agencies, according to a database maintained by the Union of Concerned Scientists. The database was last updated in January 2022. Since then, many more Starlink satellites have been added, so the real numbers are even higher. Most satellites are in a low-Earth orbit, that is, in an area less than 2,000 kilometers above the ground and where satellites – including the International Space Station – travel a full orbit about every hour and a half.
In May 2019, SpaceX began to occupy this orbit with hundreds of its Starlink satellites, which are designed to transmit Internet and cellular services around the globe. In October, according to a statistic privately run by Jonathan MacDowell, about 3450 of the total number of satellites orbiting the Earth – and thus more than half – were Starlink satellites. They start in groups and orbit the Earth in so-called constellations, that is, they are arranged in such a way that they can work together. Both the number and its brightness pose a problem for astronomy. Shortly after the start, they are best seen. Then you can observe how they flicker as a shimmering train across the twilight sky. In digital telescope cameras, they appear as bright streaks of light that obscure stars and astronomical objects, overexposing the entire field of view. "It's like driving down the street and looking through the windshield at an oncoming car with the high beam on," says Tyson. "You lose a lot of information – not only within the beam of the headlights, but everywhere, and the eyes themselves are also blinded.«
The $473 million ruby Observatory is particularly at risk from the ground-based astronomy projects. The telescope is scheduled to be put into operation in 2024, and by then tens of thousands of small to medium-sized satellites, including other starlink flocks, could be orbiting the Earth. The observatory's planned "Legacy Survey of Space and Time" will use an 8.4-meter telescope in combination with a 3.2-gigapixel digital camera, the largest camera ever built, and will take 1000 images of the sky every night for a decade. Each image will cover 9.6 square degrees of the sky, which is about 40 times the area of the full moon. The telescope is designed to detect new and potentially threatening near–Earth objects, as well as temporary events such as supernovae - and even things that no one has thought of before, as Tyson says. But these observations could be "significantly affected by the alarming pace" of new satellite deployments, according to an analysis written mainly by Tyson and published by the Rubin Observatory team in September.
In another report, which was created by the US GAO and sent to the Congress on September 29, it is found that the satellite constellations of astronomy damage and they could harm the environment if they fall back to earth. "Since more and more satellites are being brought into the earth's orbit, almost all varieties of optical astronomy could be negatively influenced," the GAO experts write. They are calling for further studies to fully evaluate the effects of satellite constellations on astronomical research, as well as new political measures that are to lead to regulations and norms. However, many astronomers fear that such regulations will not come early enough or will not be strict enough to save the floor -bound astronomy.
A further 431,713 satellites are to be launched in the coming years
The most important and best -known provider of this satellite swarms is SpaceX. The only company so far has already worked with astronomers to make its Starlink satellites darker. The company has already launched "Darksat", a light -absorbing, darker satellite, as well as anti -reflection coatings for solar collectors. So far, SpaceX has not responded to a request for comment. If you take the Starlink satellite swarms and those of other companies such as those of the British satellite operator OneWeb and the Chinese company Galaxy Space, there are currently more than 4,000 satellites in orbit that are designed for a network coverage. According to the inquiries for approval submitted to the American communication authority FCC and the international telecommunications union (the two leading telecommunications authorities in the world), a total of 431 713 satellites are to be launched in 16 constellations in the coming years.
The satellite companies point out that according to an ITU report published in 2021, about 2.9 billion people - that is, almost a third of the world's population – have never used the Internet. A constellation of communication satellites could change that. But the light of the Starlink constellation alone will give stripes to at least 30 percent of the images taken by the Rubin Observatory. If 400,000 satellites make it into orbit, every image taken in the early evening will have a streak. The British OneWeb constellation will orbit in a higher orbit than other constellations, so it will be visible throughout the night. (OneWeb also did not respond to a request for comment.) Even if software programs can erase the satellites from the images to save the pixels, data errors on the light detection chips will still be a problem. "Operating satellites in [near-Earth orbit] poses a significant danger to the main task of LSST: the discovery of what no one would have expected, " concludes the Rubin Observatory report.
Astronomers and even a private company are working on software that can remove some of the satellite strips or change the direction of the telescope to avoid them. However, this is difficult because the satellites move and appear differently in different color filters to name just a few of the problems. Meredith Rawls from the University of Washington works in a team that will in future send alarm reports for those unforeseen phenomena in the night sky that capture the ruby observatory. This could now be 10 million reports per night. Software should only automatically contact these filters and the global astronomy community only with significant events such as asteroids or supernovae, she says.
"In the stripes, you can see these small, strange bubble patterns that our software thinks is a potential object or supernova and therefore marks them. It's just a satellite," she says. This leads to more false positives than we would like, and then the guessing begins: how many? Will it be 5 per night or 500? We don't know."
Meg Schwamb, an astrophysicist at Queen's University Belfast, is the astronomer who proposed to carry out the twilight studies of the Rubin Observatory at an early stage in its ten-year life – the proposal that made Rachel Street shudder. Twilight is the time when near-Earth asteroids can be easily found and when the Rubin Observatory could discover many new asteroids. The Chelyabinsk meteor, for example, which shook everyone in 2013 when it exploded over Russia, came from a similar direction to the Sun and is exactly the kind of object for which the Rubin Observatory was developed. However, observations with partial solar irradiation will be more difficult, since the solar panels of the satellite constellations are illuminated by the Sun at this time.
"I never thought that as an astronomer I would plan to prefer observations because we don't know what the satellite field will look like," said Schwamb. As a rule, astronomers rather assume that they will extend the lifespan of their observatories and will start new, further campaigns in later years. To reverse this order and instead to ensure that some fundamental scientific work is done before the observatory is blinded by satellite light, contradicting the plans of many scientists who plan their work and even their entire career in other ways. Schwamb compares the satellite constellations with orbital advertising and argues that humanity has to find out how to control them and what they should do. "If it were not Starlink but Coca-Cola, would we agree?" She asked. "It is also a fundamental cultural question: Should Elon Musk control what people see in the night sky?"
The scientists admit that SpaceX has tried a number of methods for darkening its satellites. However, the objects are still visible and other providers do not use such mitigation strategies. In addition, the newer Starlink satellites and those manufactured by other companies are much larger and correspondingly brighter than the previous ones. A company called AST SpaceMobile launched on April 10. September, a prototype called BlueWalker 3, which may soon be the brightest object in the night sky next to the Moon. It contains a 64.4 square meter phase-controlled antenna system that can communicate directly with mobile phones on Earth and could even outshine Jupiter. AST SpaceMobile intends to launch 168 even larger satellites, called BlueBirds, in the next few years. A spokesman for the company said that the tests of BlueWalker 3 will help engineers evaluate the materials of the satellite and assess its brightness, adding that the company is actively working with industry experts and NASA to dispel concerns about brightness. AST SpaceMobile is considering anti-reflective materials and changes in operation to make the satellites darker.
The number of Bluebird satellites will be much lower overall than is common in other constellations, but they could have a different kind of problem. Some telescopes may be able to avoid very light bluebirds, as some telescopic cameras are designed to avoid bright objects such as planets or the moon. In hundreds of them, however, this becomes difficult. And a bright satellite that goes through the long exposure of a digital camera could lead to a short fire in the sensitive electronics of the camera.
"It's clear that the technology is there. If you want to destroy the night sky, you can do that," says Jonathan McDowell. It will depend on the details of the business models of these companies and the details of the regulatory environment, whether it actually happens or not. That's why we should talk about whether this is acceptable."
Global regulations are difficult
Several astronomers believe that new FCC regulations that regulate satellite communication in the USA will not be sufficient. It was only this spring that the United Nations Committee held a session on the subject of satellite swarms for the peaceful use of space (Copuos), but the process is slowly progressing. McDowell says that if Copuos sees the protection of the night sky as part of his task, then the Member States could be encouraged to use their own national regulations to enact regulations on how many bright satellites can be started and where they can be. But the hard truth is that nobody can do much at the moment to slow down the steady start of satellite constellations and its sun -reflecting solar cells.
Some people are already hoping for fate. In February 2022, when some Starlink satellites were in low orbit preparing to ascend to their final altitude, a solar flare reached Earth, triggering a plasma storm in the uppermost layers of the atmosphere. As a result, 40 satellites crashed and burned up.
The members of the Rubin Observatory team hope that private companies will build less reflective satellites in the future and operate them in lower orbit, which means that they fly faster through the image, but these decisions are up to the company; There are no laws that you oblige. Rawls thinks that companies should approach astronomers on their own and explain the goals of their projects and the possible effects on astronomy. »If a city wants to build a new bike path, it takes three years because it has to keep 700 meetings with interest groups. I would also like that for space, ”she adds. »But in a way, everyone who looks up is part of a group of interests. And that makes things a real challenge. "
But while many astronomers are seriously concerned, no one knows yet how bad it will really get — or how long the problem will last. "Very soon, the sky will be visually dominated by these satellites rather than by the stars themselves," says Anthony Tyson, "and that will be regardless of whether you live in a city or in the countryside. The future is one in which the sky sparkles constantly and everywhere, from all these satellites."
© Springer Nature Limited Scientific American, Satellite Constellations Are An existential Threat for Astronomy, 2022
