Author | Yang Chang
Edit | Li Shuiqing
Wisdom 65438+1October 18 news, last year, the satellite of China Space Station "touched porcelain" twice, and it was in trouble again. Recently, some astronomers pointed out that the satellites planned by the American space company Space Exploration Technology Company seriously affected astronomical observation.
By analyzing the images taken by the survey telescope from 20 19 to 202 1, astronomers found that the number of images affected by satellite chains increased by 35 times. With the launch of more satellite chains, they estimate that satellite chains will appear on every observation map in the future, which hinders normal scientific observation.
This is only the negative impact of less than 5% of the target number after the satellite link project is started. Space Exploration Technology Company began to implement the satellite link project in 20 19, and plans to launch 42,000 satellite links to form a satellite link network to provide satellite Internet services for the whole world. About 2000 satellites have been launched so far. As more and more satellite links are successfully launched into low-earth orbit, the threats brought by satellite links will be more and more, and the threats to astronauts and spacecraft will be greater and greater.
Zhao pointed out that the United States should respect the international order in outer space based on international law and take immediate measures to prevent such incidents from happening again. Elon musk, founder of Space Exploration Technologies, did not respond.
It is not the first time that the satellite chain has affected astronomical observation and the safety of astronauts and spacecraft. It has been pointed out many times before that too many satellite chains will interfere with astronomical observation, occupy the earth's low space orbit, increase the risk of spacecraft collision and produce a lot of space junk. However, space exploration technology company did not stop its plan because of criticism from all sides. At 8: 04 on June 65438+1October 19, Beijing time, the satellite chain will also be launched for the second time this year, which is likely to aggravate the threat to the normal observation of astronomy and the exploration of human cosmic security.
For the problems pointed out by all parties, has the star chain improved? Is it possible for China Space Station to cope with the "barbaric growth" star chain?
Since Space Exploration Technology Company launched the first batch of satellite chains in May, 2065438+2009, the astronomical community has been worried that the satellite chain plan will have an impact on astronomical observation and interfere with astronomers' discovery of various natural celestial bodies.
In order to quantify the influence of satellite chains on astronomical observation, astronomers in the United States and other countries analyzed the astronomical observation images taken by the ZTF telescope at the Paloma Observatory.
ZTF scans the whole night sky every two days to capture the image data of various stars. Astronomers found that there were 530 1 tracks in the images taken by ZTF from 20191year to September 20021year.
Orbit trajectory caused by star chain operation in astronomical observation images
With more and more satellite chains in orbit, the observation images at dawn and dusk are most affected. In 20 19, only 0.5% of such images were affected by satellite links. By 20021year, the affected images reached 18%. Astronomers estimate that at present, astronomers have a 0.04% probability of not finding them.
Astronomers predict that if the number of satellite chains in orbit reaches 6.5438+0 million, all astronomical observation images at dawn or evening will show the orbital trajectory formed by at least one satellite chain.
Other more sensitive astronomical observation instruments, the images taken will be more affected by the star chain.
As the number of satellite chains (red) tracked by astronomers increases, the number of astronomical observation images (blue) affected is also increasing.
Satellite chain not only affects astronomical observation, but also affects the exploration of space by other spacecraft, and the most serious thing is to threaten the safety of China Space Station and its astronauts.
In order to fulfill the obligations stipulated in the Outer Space Treaty, an important international law in the field of outer space, and ensure the life safety of astronauts, the Government of China informed the Secretary-General of the United Nations of the above-mentioned dangerous situation and the measures taken by China through the Permanent Mission of China in Vienna on February 3, 2026, and requested the Secretary-General to inform all States parties.
China sent a note verbale to the United Nations.
According to the information sent by China to the United Nations, the satellite chain deviated from the prescribed orbit and approached the China Space Station twice. In order to ensure the safety of astronauts in China Space Station, the China Space Station assembly has implemented two preventive anti-collision controls ("emergency anti-collision").
The note verbale described in detail the emergency avoidance of the satellite chain twice by the China Space Station.
Both the satellite chain and the China Space Station have their own fixed orbits, which are about 555 kilometers and 390 kilometers around the earth respectively. Initially, they did not cross or overlap.
The first time that China Space Station took emergency collision avoidance was in July, 20265438 1 day. During the period from May 1095 to June 24, 200212005, the satellite-195 continued to descend to an average orbital altitude of 382km and remained at that orbital altitude. Because satellites orbit around the earth with perigee and apogee, when the height ranges of two spacecraft are close, it is easy to get close and collide. July 1 day,
Less than four months after this dangerous situation occurred, China Space Station took the second emergency collision avoidance on1October 202 1 and 202 1. This time, it was because of the close contact between Star Chain -2305 and China Space Station. And this satellite is still in a state of continuous orbit change.
In the face of China's briefing, Musk did not respond specifically. However, on February 29th, local time 202165438+,Musk responded to the criticism of the Director General of the European Space Agency that the Musk satellite occupied too many orbits.
Josef Aschbach, the new Director-General of the European Space Agency, warned that Musk's lack of coordination in implementing the interplanetary link plan means that the billionaire is making his own "rules" for space. One person owns half of the active satellites in the world, which will affect the radio frequency and orbital space in space.
Musk believes that the earth's low orbit can accommodate tens of billions of spacecraft, and thousands of satellites are nothing, just like thousands of cars on the earth, so don't worry too much.
American astrophysicist mcdowell questioned Musk's statement. Spacecraft can fly at a speed of 27,000 kilometers per hour, which is longer than the time interval required for cars to run safely on the earth. Possible collisions between spacecraft can only be found when they are relatively close, and space is already crowded.
Musk's star chain plan has been implemented for several years. The earliest time is 20 15. Space Exploration Technology Company announced that it will carry out the satellite chain plan, plan to build a satellite network in space, provide satellite Internet services for the ground, provide broadband Internet services for areas lacking optical fiber and physical Internet links, and expand the boundaries for people to use the Internet.
According to the information released by Musk on social media on June 65438+1October 16, 2022, at present, there are 1469 satellites in the satellite chain, 272 satellites are entering orbit, and satellite laser link communication will be activated soon.
Each satellite in the satellite chain adopts a compact flat design, which minimizes the volume and has the function of automatic collision avoidance. It is equipped with a customized navigation sensor, an optical space laser, four phased array antennas and two parabolic antennas, as well as an efficient ion thruster and a single solar cell array.
The autonomous anti-collision device of satellite chain needs to be combined with the debris tracking system of the US Department of Defense to realize autonomous maneuver and avoid collision risk. Space exploration technology company claims that its automatic collision avoidance device is an order of magnitude higher than the industry standard.
This is how the specific autonomous collision avoidance process is realized. The ground system combines the orbit prediction information of the satellite chain and the data of the space target database to screen out the potential collision targets, calculate the probability, and then transmit the high probability collision information to the satellite. The satellite chain uses four momentum wheels perpendicular to each other to adjust its attitude, and uses ion propulsion engine to change its orbit to complete avoidance. This process is completed automatically by the computer.
Automatic anti-collision device of satellite chain and customized navigation sensor
The main function of customized navigation sensor of satellite chain is to determine the position, height and direction of each satellite, and realize the accurate delivery of broadband throughput.
Optical space laser is a device being tested by space exploration technology company, which can enable spacecraft to transmit data without local ground station, thus achieving real global coverage.
Optical space laser and satellite chain antenna
The high-efficiency ion thruster is powered by krypton, which is mainly used to help satellites maneuver and get out of orbit at the end of their life and burn in the atmosphere close to the earth.
Efficient ion thruster and solar cell array for satellite chain
In addition, in the face of astronomers' concerns, Space Exploration Technology Company redesigned the sun visor of the satellite chain to reduce its brightness, thus reducing the interference to astronomical observation.
The initial launch target of the satellite chain was 6.5438+200,000 satellites, and then 30,000 satellites were added.
At present, Space Exploration Technology Company has carried out 35 launch missions, and * * * launched 199 1 satellite chain, but some of them have been proved to be unresponsive and no longer maneuverable in orbit, and the proportion will be about 3% in 2020. These "space junk" will endanger the safety of other normal spacecraft.
1978, Donald J. Kessler, a scientist of NASA, raised the threat of a large number of spacecraft or space junk that could not operate normally. The collision of two spacecraft produces a lot of debris, which will hit other spacecraft and form more debris. Maybe the earth will be slowly surrounded by layers of space junk.
In addition to the control failure, the orbit planning of the satellite chain may also have problems. The satellite chain not only threatened the China Space Station, but also almost hit the European Space Agency's Fengshen meteorological satellite. 2065438+On September 2, 2009, Fengshen satellite almost collided with satellite chain -44, and the European Space Agency changed its orbit urgently, thus avoiding an accident.
In April of 20021year, the satellite chain was nearly 57.9 meters away from the satellite internet satellite of OneWeb Company in the UK, and almost collided. OneWeb mentioned that Space Exploration Technologies shut down the collision avoidance system on the satellite chain.
Hugh Lewis, head of the Aerospace Research Group of the University of Southampton in the United Kingdom, said that if two spacecraft pass within 0.6 miles (1 km) of each other, if the two spacecraft are in close contact and there is a danger of collision, then all satellite chains will appear about 1.600 times a week, which has accounted for 50% of all such time.
The close contact situation of spacecraft involving satellite chain satellites drawn by Hugh Lewis' team using the data of Socrates database for satellite threat assessment shows a continuous growth trend.
In short, judging from the current facts, the autonomous anti-collision ability of the star chain seems to be ineffective and somewhat "overbearing".
Space is a resource belonging to all mankind. How to regulate human space activities requires relevant international laws to coordinate the space activities of various countries.
The main body of space law is five international treaties promulgated by the United Nations Committee on the Peaceful Uses of Space, namely the Outer Space Treaty, the Rescue Agreement, the Liability Convention, the Registration Convention and the Moon Agreement.
The most important of these is the Outer Space Treaty. The Outer Space Treaty was adopted in 1966 and entered into force in 1967+00+00. The vast majority of United Nations Member States have signed and ratified this international space law.
In addition, the United Nations General Assembly has adopted a series of principles, resolutions and declarations related to space activities, the latest of which may be the Guidelines for the Long-term Sustainability of Outer Space Activities adopted by the United Nations Committee on the Peaceful Uses of Outer Space in 20 19, but this new guideline does not belong to the soft law of outer space and is not legally binding.
There are also some international organizations that have formulated relevant rules to regulate space exploration. For example, the International Telecommunication Union (ITU) is responsible for allocating satellite frequencies and orbital resources, and countries get priority in the order of declaration.
Countries have also promulgated corresponding space laws and regulations. For example, in 20 15, the United States passed the Law on Exploration and Utilization of Outer Space Resources, which stipulated that American citizens have the right to possess, own, transport, use and sell outer space resources. In 20 16, Japan promulgated the Law on Space Activities to regulate commercial space activities.
With the rise of commercial space business, some original regulations can no longer adapt to some current situations. Space sustainability and space debris are one of the key issues in space governance.
However, the service life of the satellite is limited. If it is abandoned out of control, it will become space junk and threaten other normal satellites. In 2009, the American Iridium 33 satellite collided with the scrapped Russian Cosmos -225 1, and the Iridium 33 satellite was damaged and produced a lot of debris.
For this reason, the United Nations Committee on the Peaceful Uses of Outer Space has specially issued the Space Debris Mitigation Guidelines to reduce the impact of space debris on human space exploration, which stipulates that the orbital stages of spacecraft and launch vehicles should be limited to the low-Earth orbit region for a long time after the mission.
The satellite chain plans to launch 42,000 satellites, and the service life of each satellite is only 5-7 years. It will take 1-5 years for the failed satellite to fall into the atmosphere and burn in an orbit of 550 kilometers. Once a large number of satellite links fail, it will have very serious consequences.
Spacecraft have fixed orbits, and there are differences in orbital height, orbital shape and orbital inclination. At present, the probability of satellite collision is not great.
In addition, changing the satellite orbit like a satellite chain without notifying the spacecraft in the nearby orbit will also threaten the safety of the normal operation of the spacecraft.
In the face of possible collision accidents, many spacecraft have made plans in advance, such as the emergency collision avoidance function of China Space Station. In case of emergency, the engine of the space station controls the system to lift the orbit and change the orbit height and inclination. In addition, there are protective boards to deal with small space debris outside the experimental cabins such as Tiangong 1 and Tiangong-2, and measures such as hiding and resisting are taken to deal with the impact threat.
In addition, the space garbage recycling plan has also been put on the agenda. The European Space Agency plans to go to space to recycle space junk in 2025, which may prevent those failed satellites from posing a threat to normal spacecraft.
But the more important and intractable problem is that with the development of commercial aerospace companies, more and more people are involved in space exploration, lacking supervision. Commercial space companies are making their own space rules, especially Musk's space exploration technology company. The boundary between government space research and enterprise space exploration is gradually blurred. For example, space exploration technology company and NASA have very close cooperation, so it may be more urgent to formulate space rules that most countries in the world can abide by.
Space is an area where all countries are striving to compete. In the past 202 1 year, commercial aviation continued to rise. Many commercial space companies compete to send people into space tourism, and many countries have also launched their own satellites.
However, orbit resources are limited. Whoever launches more satellites first can seize more orbits and take more initiative in space exploration. The rise of commercial space flight intensifies the situation of orbital competition, but the organization or region that launches spacecraft should also consider the issue of sustainability to avoid all kinds of adverse effects such as space junk brought by preemptive satellite launch.