Satellite "pollutes" the starry sky? The concern of the astronomical community is not unreasonable.

Since Space Exploration Technology Company launched the first batch of StarLink satellites, a "starry train" has appeared in the night sky like never before, causing a series of problems, worries and doubts around the world.

Astronaut: The attitude of the satellite is still unstable, and the light pollution will be reduced in the future.

Zhou Xin, manager of Micro-Nano Star Technology Co., Ltd., analyzed that at present, the influence of satellites on ground observation includes two forms: occlusion and reflection. But objectively speaking, the effect of occlusion is usually not obvious. For a satellite with a wingspan 10 meter running at an altitude of 500 kilometers, the maximum viewing angle on the ground is only about 4 seconds, while the visual resolution of ordinary people is between 3-5 minutes (180-300 seconds), so it is almost impossible for naked eyes to find a fast-moving point blocking the night sky. The International Space Station, of course.

"In addition to the occlusion effect, if the satellite reaches a specific orbit and angle, it may just reflect the sunlight to the ground, and the ground will be easy to observe." He said that for most satellites, because the satellite power comes from solar cells, the largest part of the satellite, the solar wing, always faces the sun, and the probability that the reflected light of other parts is observed by the ground is actually very low; On the other hand, in recent years, some companies at home and abroad (such as Russia's Start Rocket Company) have tried to engage in some commercial or entertainment activities, such as advertising and publicity. In the form of self-luminous or reflected sunlight through satellites. Such an intentional satellite may indeed have a relatively obvious impact on astronomical observation on the ground.

Zhou Xin believes that the influence of satellites in normal operation on the night sky is almost imperceptible. Although it can be observed with the help of telescopes and other equipment, considering that the speed of satellites in near-earth orbit is above 7 km/s, the interference effect will soon disappear from the field of vision. For professionals, satellite orbit data can be modified and deleted accordingly. Orbital data of all known satellites are recorded on the NORAD website. On the other hand, satellites designed to produce ground visual effects may indeed have a more obvious impact.

According to the analysis of scientists, there are two reasons for observing a large number of satellite chains at present: first, the satellites have not established a stable attitude, and the solar wing has not completed the orientation of the sun, and the reflection effect produced by the solar wing in a large area is more obvious; Second, the satellite is still in the deployment stage, and it has not been completely "rolled out" in space, so it is easy to be observed. Later, as the satellite gradually established a stable attitude and the satellite constellation was deployed, the observed situation would be less and less.

Astronomer: There is radiation and debris, which will inevitably affect astronomical observation.

Zhao Haibin said that the space station and other targets will also pollute the observation images, and related artificial objects can be seen in the astronomical observation images, which will affect the local star field. In fact, the passing of aircraft will also affect astronomical observation, and the pollution will be even greater. Projects like the Star Chain Project will "pollute" a certain sky area at a certain time, thus reducing the availability of this sky area when astronomers observe.

"In addition to the impact on radio astronomy, a large number of satellite networking projects have a great impact on the entire space environment." Galla said that the 12000 satellite chain mainly runs in the orbit with a height of 500 km to 600 km, which makes the satellites near the orbit very crowded, greatly increasing the probability of collision with each other, thus causing more space debris. If some corresponding mitigation measures are not taken, if an explosion chain reaction occurs, it will lead to the unsustainable use of space.

Solution: Introduce normative measures to promote the development of space and astronomy.

"The concern of the astronomical community is not completely unreasonable." Yang, executive director of Hainan Institute of Institute of Aerospace Information, China Academy of Sciences, believes that both the astronomical community and the aerospace community should analyze the problem objectively and dialectically. With the development of space technology, the cost of all aspects will be greatly reduced, and so will the cost of astronomical observation. The aerospace industry should give full consideration to minimize pollution, and the astronomical community can also consider putting the observation platform in outer space if conditions permit.

"The light pollution caused by satellite deployment should be solved by some technical means." The chief operating officer of Caifu (Hangzhou) Technology Co., Ltd. said, "And satellites are also an effective means of astronomical observation. Making full use of new technology can achieve better astronomical observation. The development of the satellite industry will have a positive effect on the development of astronomical satellites. "

Gallas thinks it is a good idea to transfer the observatory from land to space in order to reduce interference. This will have many advantages, avoiding the restrictions of geography, weather, atmosphere and light pollution in ground-based observation, and obtaining more accurate observation data under the same instrument performance index. GAIA satellite, NEOWISE satellite, etc. Only the sky survey observation equipment and near-earth object observation equipment were moved from the ground to space, and more effective observation data and richer scientific output were obtained.

How to reduce interference from the source? Not long ago, Elon, CEO of Space Exploration Technology Company? Musk once responded to the "star-watching pollution theory", saying that he had instructed the star chain team to study how to reduce the satellite reflectivity. The next batch of satellite chains is likely to reduce or even completely eliminate star flicker.

Galla said that at present, three international organizations have issued laws and regulations on restraining the generation of space debris and protecting the sustainable development of the space environment, but none of them is too binding. At the same time, the European Union, the United States, the Russian Federation, China and other countries have also formulated relevant regional or national policies to ensure the sustainable development of space activities. At present, most of the policies and regulations formulated by various countries are aimed at suppressing debris in three stages: space launch, satellite on-orbit mission operation and post-mission disposal. From the perspective of astronomical observation, it is mainly the local government that will formulate corresponding local rules and regulations in order to protect the observation environment of ground stations. For example, in order to ensure rapid observation, Guizhou Province has specially formulated a series of local laws and regulations, such as the Measures for the Protection of Electromagnetic Quiet Zone of Guizhou 500-meter Spherical Radio Telescope.

Gallas believes that the rise of commercial aerospace is the general trend and cannot be avoided. As an administrative department of the government, it should formulate corresponding normative measures to guide the orderly development of commercial aerospace norms. It can not only give play to its advantages, but also make aerospace and astronomical research develop harmoniously.