US-China row over Elon Musk’s Starlink satellites shows need for space cooperation

The near-misses between Starlink satellites and China’s space station highlight the growing danger of collisions in near-Earth orbit
With tens of thousands of satellites set to enter orbit, states must act now to improve communication and risk management in space

Jinyuan Su

Published: 3:30am, 7 Jan 2022

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China’s Tiangong space station had to implement “preventive collision avoidance controls” on July 1 and October 21 last year to avoid two Starlink satellites, according to a diplomatic note from China to the UN secretary general on December 3. Starlink is operated by SpaceX, owned by Elon Musk.

In the note, China detailed the two incidents and asked the secretary general to circulate the information to all parties to the Outer Space Treaty and bring to their attention the obligations under Article VI.

The treaty, negotiated during the Cold War, remains the cornerstone of international space law. Article VI says that parties shall bear international responsibility for national activities in outer space, including those carried out by non-governmental entities. Both China and the US are parties to the treaty.

During a press conference on December 28, Foreign Ministry spokesman Zhao Lijian told the US to “respect international order in space based on international law, take prompt measures to prevent such incidents from recurring, and act responsibly to safeguard the safety of in-orbit astronauts and the safe and steady operation of space facilities”.

At a press briefing the same day, US State Department spokesman Ned Price declined to respond specifically to China’s claims. He said the US has “encouraged all countries with space programmes to be responsible actors, to avoid acts that may put in danger astronauts, cosmonauts, others who are orbiting the Earth or who have the potential to”.

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Musk told the Financial Times on December 29 that there was room for “tens of billions” of satellites in orbit around the planet, denying claims he was squeezing out rivals in space. That came after Josef Aschbacher, the new head of the European Space Agency, warned that the large number of Starlink satellites would result in crowding other operators out of low-Earth orbits.

SpaceX has launched more than 1,900 Starlink satellites, of which about 1,800 are in orbit and providing internet services. This forms only a small part of SpaceX’s ambitious plan to provide satellite-based internet globally.

It has received permission from the US Federal Communications Commission to deploy 12,000 satellites in several shells of low-Earth orbits. In addition, it has applied to deploy another 30,000 satellites.

The number of close encounters between two spacecraft has increased dramatically since the deployment of Starlink’s satellites began in May 2019.

According to Hugh Lewis, head of the Astronautics Research Group at the University of Southampton, Starlink satellites are involved in about 1,600 close encounters between two spacecraft every week, making up about half of all such incidents.

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The situation can only get worse as tens of thousands of satellites are deployed by SpaceX and other operators, with the likes of the International Space Station and China’s space station facing the highest risk of collision.

Starlink satellites are capable of adjusting their trajectories during flight and will be removed from orbit at the end of their life. They are also equipped with an automated collision avoidance system to keep them away from other spacecraft.

However, it’s unclear just how reliable this cutting-edge technology is. Even if it works, collision avoidance cannot be guaranteed when the other spacecraft also implements avoidance manoeuvres and there is insufficient coordination.

This seems to be the case in the close encounter between Starlink-2305 and the Chinese space station on October 21. Beijing said in its note verbale that “as the satellite was continuously manoeuvring, the manoeuvre strategy was unknown and orbital errors were hard to be assessed”.

States have negotiated a set of guidelines for the long-term sustainability of space activities. These require conjunction assessments to be performed for all spacecraft capable of adjusting trajectories during orbital phases of control flight.

The guidelines are not legally binding but nations can be expected to fulfil this requirement given that it is for the safety of their spacecraft. They are obscure at best when it comes to sharing information, indicating the lack of a clear consensus. There is no uniform international regime for the sharing of conjunction assessment information.

The Joint Space Operations Centre does provide warnings to satellite operators of close orbital passes. However, this doesn’t seem to have happened in the encounter between Starlink-2305 and China’s space station, according to Beijing’s account of events.

With such encounters projected to increase dramatically, improved communication between satellite operators and the establishment of an international mechanism for conjunction assessment notification are needed.

Why China reacted so strongly to near-misses in space

Another facet with respect to satellite encounters is rendezvous and proximity operations (RPOs). In these, one spacecraft approaches another deliberately to conduct certain activities, whether to cooperate in operations such as debris removal and satellite refuelling, or for hostile purposes such as spying and interference.

Starlink-1095, which came close to China’s space station on July 1, did not seem to follow a normal deorbiting trajectory.

The satellite had been operating at an altitude of about 555km since April 19, 2020. Between May 16 and June 24 last year, it began steadily going out of orbit, down to an altitude of about 382km, slightly below that of China’s space station. Instead of continuing to deorbit, it stayed at that altitude and even rose on July 1.

In this case, the automated collision avoidance system does not seem to have worked. Given that Starlink-1095 was already below the orbit of China’s space station, surely it would have been safer to descend further, rather than going back up, to avoid a collision.

The legality of non-cooperative rendezvous and proximity operations is under intense debate, with little consensus among states or academics. Despite the disagreements, it is at least widely agreed that such operations can be highly risky and easily lead to miscalculation and escalation. Thus, there is an urgent need to find ways to manage the risks.

Jinyuan Su is a professor at Wuhan University Institute of International Law, and lead expert of air and space law at Wuhan University Academy of International Law and Global Governance, China