SpaceX Starlink satellites twice came too close, China tells UN chief

All parties to Outer Space Treaty must remember pledge to act responsibly, China tells UN secretary general in diplomatic note
SpaceX says its Starlink satellites are equipped with autonomous orbit-changing features to avoid collisions

Science

Liu Zhen

Published: 10:30pm, 27 Dec 2021

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China has complained of “close encounters” with Elon Musk’s space programme, with SpaceX Starlink satellites twice approaching the Chinese Space Station (CSS) in orbit.

The two events, on July 1 and October 21, forced the Chinese spacecraft to undertake avoidance manoeuvres to avoid collision.

Both times there were crew members on board, “which could constitute a danger to the life or health of astronauts”, the Chinese delegation said in a diplomatic note presented to the United Nations secretary general earlier this month.

The CSS “Tiangong” has stayed in a near-circular orbit at an altitude of around 390km on an orbital inclination of about 41.5 degrees since it was launched on April 29.

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From May 16 to June 24, the Starlink-1095 satellite maintained a steady descent from its original 555km-altitude orbit to around 382km, and then stayed there, posing the risk of potential collision. The CSS was forced to conduct an evasive manoeuvre on July 1 when the two spacecraft had a close encounter, said the note posted on the website of the UN Office for Outer Space Affairs.

The other satellite, the Starlink-2305, similarly continuously changed its orbit in October with an “unknown” manoeuvre strategy and unassessable orbital errors, again forcing the CSS to implement collision-avoidance control, it said.

According to satellite tracking information, Starlink-1095 continued to descend until it re-entered the atmosphere and burnt out in September, while the Starlink-2305 climbed from a 350km orbit to 550km from October to November.

When two spacecraft are orbiting at the same height, there is a risk of crossing paths and collisions.

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China said in the note that it wanted the UN to remind all state parties to the Outer Space Treaty of the pledge to “bear international responsibility for national activities in outer space … whether such activities are carried on by governmental agencies or by non-governmental entities”.

US entrepreneur Musk is the founder-CEO of SpaceX (Space Exploration Technologies), which operates the Starlink internet satellites and has already sent more than 1,900 into space since 2019.

The Starlink network plans to have more than 42,000 satellites in orbit when complete, which from the start has raised concerns about its overcrowding of the orbit, safety threats to other spacecraft and the negative impact on astronomical observations.

In March, SpaceX signed an agreement with US space agency Nasa, promising to steer Starlink satellites out of the way if they got too close to the International Space Station (ISS) or other Nasa spacecraft. It also agreed to launch its satellites into initial orbits that did not come within three miles (5km) of the ISS or other Nasa spacecraft.

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The ISS, operating at about 420km from the ground since 1998, also has performed numerous avoidance manoeuvres to dodge space debris, most recently a US rocket fragment on December 1.

SpaceX has said that its Starlink satellites are equipped with autonomous orbit changing features to avoid collisions, and that other spacecraft do not need to manoeuvre in case of an encounter.

Apart from SpaceX, other commercial companies have also announced plans to further populate space with their own internet service constellations, including Amazon, OneWeb and Telstar.