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How do astronomers overcome the damage caused by satellite giant constellations?

For thousands of years, every time we face the cloudless and moonless night in Wan Li, all mankind can witness all the beauty of the dark and primitive sky. From anywhere on earth, you can see thousands of stars at the same time, as well as the intricate features of the Milky Way, a few other galaxies, and even many nebulae, star clusters and other deep space objects. With the advent of telescopes and later photographic technology and equipment, these numbers exploded. Our view of the distant universe is limited only by our technology and investment.

But two developments have changed this situation. The first is electric lighting, which causes cities, towns and even rural areas to emit more light from the ground than everything in the sky combined. At present, only a small part of the population on the earth can see hundreds of stars with the naked eye at night. But the second development-artificial satellite-has only recently appeared, and it has only affected the night sky since the space age. By the beginning of 20 19, there will be about 2,000 satellites in service; By the end of this century, this number is expected to exceed 65438+ 10,000. This will not only change astronomy forever, but also change the relationship between human beings and space forever. In the past few weeks, both the American Astronomical Society and the European Astronomical Society held summer meetings, and many scientists and professionals shared the latest news and challenges in the cross-field of satellite and astronomy. This is what everyone should know.

Space is a big place, but low earth orbit is not. Once we venture outside the earth's atmosphere, we find that we are no longer confined to a small space above the earth's surface, but can occupy any position in our favorite three-dimensional space.

Over hundreds of kilometers, orbiting satellites can remain stable for months, years, decades or longer, depending on their equipment. The farther you go, the more earth you can cover at a time, but the closer you are to the earth, the better. The closer you get:

However, the downside is that low Earth orbit is already full of active and inactive satellites, as well as most of our space debris. The closer you are to the earth, the more satellites you need to cover the whole world. Moreover, especially if you place more satellites in a narrow space between about 300 km and about 600 km above the earth's surface (the lowest near-earth orbit), the greater the risk of collision between satellites, and the higher the possibility of a collision chain reaction caused by a single collision.

The LSST of Vera C Rubin Observatory shown in photo 20 18 is currently under construction and is close to preparing for the first observation. Even if the satellite darkens and the sun visor and orbit height follow the established plan of Space Exploration Technology Company, this world-class and unprecedented observatory will be forced to change its operation mode and consider Starlink. (LSST Project/National Science Foundation /AURA)

Astronomy before 20 19. Although both light pollution and satellites have affected astronomy, we have had some relatively successful mitigation measures to deal with them for a long time. Our state-of-the-art ground-based telescopes were built mainly under the protection of dark skies and the support of local communities-at least in the past half century. Space-based telescopes are largely unaffected by land light pollution, and occasional satellites, whether weak or bright, will only temporarily affect the image of 1%, even if a large wide-field telescope is used.

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On 20 19165438+1October 18, about19 Starlink satellites passed by Cerro Tololo American Observatory, which interfered astronomical observation in a real and measurable way and hindered scientific research. If the current plans of Space Exploration Technologies, OneWeb and other satellite providers go according to plan, the impact on astronomy will be extraordinary. (CLARAE MART？ NEZ v? Vá zquez/CTIO)

For thousands of years, every time we face the cloudless and moonless night in Wan Li, all mankind can witness all the beauty of the dark and primitive sky. From anywhere on earth, you can see thousands of stars at the same time, as well as the intricate features of the Milky Way, a few other galaxies, and even many nebulae, star clusters and other deep space objects. With the advent of telescopes and later photographic technology and equipment, these numbers exploded. Our view of the distant universe is limited only by our technology and investment.

But two developments have changed this situation. The first is electric lighting, which causes cities, towns and even rural areas to emit more light from the ground than everything in the sky combined. At present, only a small part of the population on the earth can see hundreds of stars with the naked eye at night. But the second development-artificial satellite-has only recently appeared, and it has only affected the night sky since the space age. By the beginning of 20 19, there will be about 2,000 satellites in service; By the end of this century, this number is expected to exceed 65438+ 10,000. This will not only change astronomy forever, but also change the relationship between human beings and space forever. In the past few weeks, both the American Astronomical Society and the European Astronomical Society held summer meetings, and many scientists and professionals shared the latest news and challenges in the cross-field of satellite and astronomy. This is what everyone should know.

Since 20 19, thousands of man-made objects, nearly half of which have been launched, have occupied near-and medium-earth orbits. Each black dot in this image shows a running satellite, an inactive satellite or a large enough fragment. The current and planned 5G satellites will greatly increase the number and influence of satellites for optical, infrared and radio observation from the Earth and for Earth observation from space, and increase the possibility of Kessler syndrome. Geosynchronous satellites are 50 to 100 times farther than the lowest earth orbit satellites shown here. (NASA illustration provided by Orbital Debris Program Office)

Space is a big place, but low earth orbit is not. Once we venture outside the earth's atmosphere, we find that we are no longer confined to a small space above the earth's surface, but can occupy any position in our favorite three-dimensional space.

Over hundreds of kilometers, orbiting satellites can remain stable for months, years, decades or longer, depending on their equipment. The farther you go, the more earth you can cover at a time, but the closer you are to the earth, the better. The closer you get:

However, the downside is that low Earth orbit is already full of active and inactive satellites, as well as most of our space debris. The closer you are to the earth, the more satellites you need to cover the whole world. Moreover, especially if you place more satellites in a narrow space between about 300 km and about 600 km above the earth's surface (the lowest near-earth orbit), the greater the risk of collision between satellites, and the higher the possibility of a collision chain reaction caused by a single collision.

The LSST of Vera C Rubin Observatory shown in photo 20 18 is currently under construction and is close to preparing for the first observation. Even if the satellite darkens and the sun visor and orbit height follow the established plan of Space Exploration Technology Company, this world-class and unprecedented observatory will be forced to change its operation mode and consider Starlink. (LSST Project/National Science Foundation /AURA)

Astronomy before 20 19. Although both light pollution and satellites have affected astronomy, we have had some relatively successful mitigation measures to deal with them for a long time. Our state-of-the-art ground-based telescopes were built mainly under the protection of dark skies and the support of local communities-at least in the past half century. Space-based telescopes are largely unaffected by land light pollution, and occasional satellites, whether weak or bright, will only temporarily affect the image of 1%, even if a large wide-field telescope is used.

Part of the reason why astronomers reduce the influence of satellites is through tracking plans. Because of human's understanding of the law of gravity and the influence of the earth's exosphere on satellite decay, and the thoroughness and accuracy of our tracking of objects there, astronomers can plan their observation every night to minimize the interference of satellites in collecting valuable scientific data. Since there are only a few thousand satellites, even inactive satellites and large pieces of space debris, the combination of these different interventions enables astronomers to minimize losses.

Satellite giant constellation. However, from 20 19, the situation began to change dramatically. The first launch of space exploration technology company's new Starlink satellite is the first of a series of satellite giant constellations aimed at providing modern global internet coverage, which is a direct impact on astronomy and civil circles. These new satellites are:

Space Exploration Technologies alone plans to deploy a total of 42,000 satellites in low earth orbit. Although they have made some mitigation measures, their current satellites are still barely reaching or slightly below the threshold visible to the naked eye in the dark sky. When considering other planned suppliers-including OneWeb, Kuiper/Amazon and projects from China, Japan and other countries-according to Dr. Connie Walker of the National Science Foundation NOIRLab, it seems that there may be more than 65,438+000,000 satellites in our short-term future.

On the astronomical night, the number of satellites visible in the simulated 10000 satellite constellation of 500 km (orange) and10000 km (blue). Notice how the earth's shadow reduces the influence of low-altitude satellites to a few hours at night. Even in summer, high-altitude constellations will never reach this sign. (Pat Setzel, published in AAS237)

But so far, the biggest damage is caused by professional astronomy. Every satellite that passes through the field of view of modern telescopes will:

The loss of science cannot be measured, but the realistic estimate is dramatic. The upcoming Vera C Rubin Observatory-the largest, fastest and widest all-day survey ever designed-will have satellite tracks in its estimated 30-40% images. It is most suitable for measuring the objects that are most affected by the orbits of these satellites: objects that change with time, objects whose positions change with time, and instantaneous objects that brighten and/or darken with time. Identifying and tracking potentially dangerous asteroids may no longer be possible, and we will almost certainly lose some scientific discoveries that we don't even know about.