The Chinese space station is forced to "emergency avoid collisions" twice a year, experts: space traffic rules should be established

On December 28, Foreign Ministry Spokesperson Zhao Lijian presided over a regular press conference. At the meeting, Zhao Lijian confirmed that in July and October this year, the Starlink satellite launched by the US Space Exploration Technology Company approached the Chinese space station twice. During this period, Chinese astronauts are on missions inside the space station, and for safety reasons, the Chinese space station has taken emergency collision avoidance measures.

According to the official website of the United Nations Committee on the Peaceful Uses of Outer Space, on December 3, the Permanent Mission of China to the United Nations and other international organizations in Vienna sent a note verbale to the Secretary-General of the United Nations, informing them of the incident that posed a danger to the lives and health of astronauts carried on the Chinese space station. The note pointed out that the Chinese space station assembly implemented preventive collision avoidance control ("emergency collision avoidance") for the US Starlink satellites on July 1 and October 21, respectively.

"Just like traffic lights, when to go, left or right, space also needs to have such a traffic rule to ensure the safety of satellites in orbit." Aerospace expert Huang Zhicheng said in an interview with the Beijing News reporter.

The U.S. "Starlink" program built by 12,000 satellites

In January 2015, Musk, CEO of SpaceX, proposed a "StarLink" plan to launch 12,000 satellites into low Earth orbit between 2019 and 2024 to build a giant three-tier satellite network. These three layers are located in orbits 340 kilometers, 550 kilometers and 1150 kilometers above the ground, respectively, and eventually connect all satellites into a huge "constellation" that provides all-weather, high-speed, low-cost satellite Internet services covering the entire earth( including the north and south poles).

Huang Zhicheng introduced that the formation of the "Starlink" plan is basically divided into three steps. The first step is to complete the initial coverage with 1584 satellites, the second step is to complete the global networking with 2825 satellites, and the third step is to form a more complete low-orbit constellation with 7518 satellites.

In 2019, the Federal Communications Commission submitted a plan for 30,000 small satellites operating in low orbit to the International Telecommunication Union (ITU) on behalf of SpaceX. To date, SpaceX has launched more than 1,900 Starlink satellites. "From an objective point of view, the more satellites they launch into space, the more they will bring harm to the future operation of the Chinese space station." Huang Zhicheng said.

Not every Starlink satellite that has been launched is operating normally. Huang Zhicheng introduced that among the starlink satellites that SpaceX has launched, 169 have been damaged and become space junk.

"In the Starlink satellites, each satellite weighs about 227 kg and has a compact flat design that minimizes volume. Launched in a self-stacking design stacked in the fairing, no dedicated multi-star adapter is required. The satellite uses a single-wing solar display, which greatly simplifies the system, standardizes the solar cells, and makes it easier to integrate into the manufacturing process. Huang Zhicheng said.

In addition, the satellite is equipped with a highly efficient ion thruster driven by krypton, allowing the satellite to maneuver in space and de-orbit at the end of its useful life.

Huang Zhicheng said that although the Starlink program is a commercial low-orbit satellite constellation program, it can provide low-cost, global coverage of high-speed Internet services, which have the ability to launch omnidirectional beams to telemetry, track and control spacecraft.

In the field of aerospace, orbital position and spectrum resources are a limited natural resource, and satellite companies need to apply to the relevant agencies for eligibility in the form of declarations. According to the International Telecommunication Union (ITU), orbital positions and spectrum resources are allocated primarily on a "first-come, first-served" basis, and late-declarants cannot adversely interfere with the satellites of the first-to-filers.

But "first come, first served" is also restricted. "The launch mission needs to be completed within a certain period of time, and if it is timed out, this application will be disqualified." Huang Zhicheng said.

This year, the Chinese space station has twice "emergency avoided collisions" starlink satellites

According to the Chinese note, in 2021, China's manned space project has carried out five launch missions and successfully launched the space station Tianhe core module, Tianzhou-2 and Tianzhou-3 cargo spacecraft, Shenzhou XII and Shenzhou 13 manned spacecraft into orbit. The Chinese space station assembly is stable in a near-circular orbit with an altitude of nearly 390 kilometers, with an orbital inclination of about 41.5°.

The U.S. Starlink-1095 satellite has been operating steadily since April 19, 2020, in an orbit with an average altitude of about 555 kilometers. From May 16 to June 24, 2021, the satellite continued to de-orbit maneuver to an average orbital altitude of 382 kilometers, and remained operating at that orbital altitude. On July 1, the satellite experienced a close-up event between the Chinese space station. For safety reasons, the Chinese space station took the initiative to avoid collisions on the evening of July 1, avoiding the risk of collision between the two targets.

On October 21, 2021, the Starlink-2305 satellite had a close proximity incident with the Chinese space station. Given that the satellite is in a continuous orbit maneuver, the maneuvering strategy is unknown and the orbital error cannot be assessed, and there is a risk of collision with the space station. In order to ensure the safety of astronauts in orbit, the Chinese space station once again implemented emergency collision avoidance on the same day, avoiding the risk of collision between the two targets.

What is "emergency avoidance"? Huang Zhicheng explained that this refers to an emergency, the electric engine equipped with the space station through the system control to lift the orbit, change the orbit height and inclination, to avoid collisions with other satellites.

In February 2009, the United States Iridium 33 hit the obsolete Russian "Cosmos-2251" satellite at an altitude of nearly 800 kilometers over Siberia, the first satellite collision in the history of human spaceflight. Specific to the Starlink satellite, in 2019, the Starlink-44 satellite fell to an altitude of 320 kilometers, almost colliding with the European Space Agency's "Fengshen" Earth observation satellite at that time, and the "Fengshen" satellite urgently changed its orbit to avoid risks. In July, the Russian Space Agency issued a statement saying that the Starlink satellite and a piece of Falcon 9 rocket booster debris could hit its cargo spacecraft delivering supplies to the International Space Station.

Experts: The boundaries between military and civilian use in space are gradually blurring, and potential conflicts may occur at any time

"In orbit at the same altitude, the probability of two spacecraft with different inclinations colliding is relatively small, but there are still some." Huang Zhicheng said that at present, SpaceX launches satellites with an orbital altitude of about 550 kilometers, "intentionally" or "unintentionally" to reduce the height of satellites, when the satellites fall to an altitude of about 390 kilometers, it will inevitably have an impact on China's space station.

In accordance with article 5 of the Outer Space Treaty concluded in 1967, States Parties shall immediately notify the other States Parties or the Secretary-General of the United Nations of any phenomenon discovered by them in outer space, including the Moon and other celestial bodies, which could pose a danger to the life or health of astronauts.

"NASA, on the other hand, signed an agreement with SpaceX. If the distance between the spacecraft is 5 kilometers, there is a problem. In the event of a collision, all responsibility lies with SpaceX, which must notify NASA a week before the satellite makes a maneuver. Huang Zhicheng said.

It is understood that since its inception, the United Nations Committee on outer space and its Legal Subcommittee have formulated five major international conventions on outer space activities, namely: the Treaty on Principles To Be Followed by States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, which entered into force in 1967 (hereinafter referred to as the Outer Space Treaty); Convention on International Liability for Damage Caused by Space Objects (the Liability Convention), convention on registration of objects launched into outer space (the Convention on Registration), which entered into force in 1976, and the Agreement governing the activities of States on the Moon and other celestial bodies (the Agreement on the Moon), which entered into force in 1984.

The WeChat public account of the Department of Articles and Laws of the Ministry of Foreign Affairs has mentioned that the Chinese government has always strictly followed the Outer Space Treaty, the Rescue Agreement, the Liability Convention and the Registration Convention to which it has acceded to, and has earnestly fulfilled its treaty obligations.

"None of these international conventions deals with the 'rules of space traffic,' but every year there are discussions by countries to establish rules for space traffic." Huang Zhicheng said that with the increase in the degree of commercialization of space, the boundaries between military and civilian uses in space are becoming more and more blurred, and potential conflicts are likely to occur at any time. "The management of satellites in orbit is an extremely complex issue, and we should first establish space traffic rules to create a safe and orderly space environment."

Beijing News reporter Zhang Jianlin

Edited by Bai Shuang proofread by Chen Diyan