Scientists will need additional software, new cameras, and much more money to cope with the interference due to the Starlink system.
Starlink satellites interfere with telescope observations in Chile. It seems that astronomers will have to adapt to a brighter and more dynamic sky. Photo from NSF’s National Optical-Infrared Astronomy Research Laboratory / CTIO / AURA / DELVE.
During summer observations of stars in the countryside, it’s quite a common sight when a few satellites sweep through the sky. However, in the coming years, owners of aquiline vision will see them already in hundreds. And for professional astronomers, research will never be the same again.
This article was written with the support of EDISON.
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The battle for Earth between satellite Internet providers continues. SpaceX leads with its Starlink satellite fleet, designed to provide high-speed communications for anyone on the planet. The company has already put into orbit more than 350 vehicles, 60 of which were launched just a couple of weeks ago. Ultimately, it is planned to create a mega-group of tens of thousands of satellites, to which additional swarms from Amazon and the British company OneWeb will join. Since the first strings of bright new lights stretched overhead, astronomers have been worried about the future of their sphere. And now, one of the most voluminous analyzes of the movement of the future 12,000 Starlink satellites has brought both good and bad news.
The extent of satellite damage to astronomical research will vary by project and observatory. The celestial settlers do not pose a significant threat, but their presence will certainly become an important factor for the near future astronomy. “This is an awakening call for astronomers in general, it’s time to start thinking about mitigating measures,” says Jonathan MacDowell, an astrophysicist at Harvard-Smithsonian Center for Astrophysics and author of the analysis.
SpaceX founder Elon Musk claims that Starlink is not a danger to scientific progress. “I’m sure that we will not affect astronomical discoveries in any way, there will be zero influences,” he said at a recent conference. “If it is still above zero, we will take corrective actions.”
The company collaborates with various astronomical organizations to minimize its impact on the night sky, but to completely eliminate this effect seems almost impossible. In fact, according to a report by McDowell, which is under consideration in the journal Astrophysical Journal Letters, the near-Earth environment is already feeling some impact. While thousands of satellites have so far launched into the Earth’s orbit (many of them no longer exist), the zone SpaceX claims to be relatively empty. Before the first launch of Starlink, less than a year ago there were only 400 large satellites orbiting at low altitude (less than 370 miles). Starlink satellites nearly doubled this number today, and that’s only three percent of what they planned.
12,000 low-flying Starlink satellites would be visible in the sky with the naked eye. MacDowell constructed a simulation that takes into account the size, height, number, and observed brightness of satellites based on data that the community of amateur astronomers helped him. He then calculated how many satellites would pass overhead at different points throughout the night, for different seasons and places around the globe. Urban residents won’t notice anything, but according to McDowell’s model (which is based on FCC SpaceX applications), star watchers in the countryside will see the horizon teeming with hundreds of dull spots due to sunlight cast off from the metal surfaces of satellites, tens of which will pass right above your head. The exact number of visible satellites will depend on different conditions, but will peak in the first hours after sunset in summer – and this is just the best time to observe the sky.
Fortunately for amateur astronomers, SpaceX is experimenting with blackening the side of its satellites facing the Earth in black to reduce their reflectivity. The company launched its first Darksat prototype in January, and it appears to be about 2.5 times dimmer than its shiny counterparts, according to a preprint published on Monday based on one pair of observations. MacDowell says that this brightness will be further reduced, probably bringing the satellites closer to the edge of the visible spectrum for human vision. Perhaps, when observing the sky, you will feel a disorienting feeling of elusive movement, but even if you squint strongly, you probably will not be able to distinguish glare.
“That will probably be enough to keep a clear sky for observation with the naked eye,” says MacDowell. “But this is not enough to preserve professional astronomy.”
The astronomical community is a very diverse group that studies everything from flying nearby cobblestones to distant black holes, and Starlink effects will be different for different situations. Some research projects, especially those that fall on late winter nights, barely notice what SpaceX adds to the sky. At this time, the Sun is as far away from the night side of the Earth, and no reflecting sun’s rays reach the satellites. This was a relief to MacDowell. “At first I was overly pessimistic,” he says, “but the fact that everything is not so bad in winter is very important. I was glad and surprised when I saw this. “
The bad news is that Starlink components will shine brightly in the telescope mirrors in the first and last hours of the night, when the sun is just below the horizon, especially in summer. These conditions are ideal for observing objects near the Sun, including the shooting of asteroids, including those that may someday collide with the Earth. Such projects simply cannot be implemented in mid-winter. “If you limit yourself only to winter observations,” says MacDowell, “then, in fact, half of the sky is lost.”
McDowell in his calculations assumes monthly launches of satellites, and ultimately – every two weeks. Researchers are beginning to prepare for the rapidly approaching future of Starlink.
The easiest way to filter out unwanted bands left by satellites in astrophotography is to use software. If astronomers take five pictures of the target, and if the satellite falls into a couple of frames, researchers can combine the photos together to erase the satellite. This method will work best for observatories with fewer satellites overhead, that is, for those located in the southern hemisphere, and will save valuable observation time for collecting really useful data.
Other observatories will need specialized equipment. For example, a system in which small cameras surround the main mirror of a telescope with a ring can give the instrument a sense of peripheral vision. When cameras detect an approaching satellite, they can click the shutter in the telescope’s field of view, temporarily blinding it until the spacecraft disappears. Projects aimed at dim objects using exposure times far in excess of short bursts of passing satellites will benefit from such a scheme.
Ultimately, each of the many observatories in the world will have to go through a period of trial and error to find out the optimal strategy that best matches the location and specification, depending on what kind of problems will arise. “It will change the environment so much that there will be unexpected consequences that we didn’t even think about,” says MacDowell.
But even if the observatories can find the substantial funding needed to support longer observations and new equipment, there is a limit to how astronomers can adapt to the sky, full of new moving light sources. At some point, if each image has several satellite bands, astronomy will simply stop. McDowell suggests that researchers will be able to adapt to tens of thousands of obscured Starlink satellites, but stresses that in the long run, astronomy will require an international treaty limiting the total number of satellites to survive.
“I think the compromise between astronomers and space researchers is that we need to work out some mitigation measures for a much more crowded sky,” he says, “but the space community must ultimately establish a limit on how dense it can to be heavenly traffic. ”
SpaceX ignored the request for comment on McDowell’s analysis. The scientist himself praises the company for its conscientious demonstrations, such as the development of Darksat and consultations directly with the Vera Rubin Observatory, the flagship building that will go into operation in 2022. He hoped that additional measures, such as painting the darksat antennas black, would help minimize interference with astronomical observations.
“I’m less worried now than recently,” he says. “But, nevertheless, very soon our sky will be greatly transformed.”