By Adam Smith,
Published by The Independent, 20 August 2021
Once Starlink launches its full 12,000 satellite network it will be involved in 90 per cent of all close approaches, which experts say is ‘getting out of control’
Craft from the space company, which was founded by Elon Musk, are involved in approximately 1,600 close encounters every week says Hugh Lewis, the head of the research group. A close encounter is when two craft pass within one kilometre of each other. Excluding the company’s own craft, Starlink passes a craft 500 times every week.
Lewis made the estimates based on data from the Socrates (Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space) database, which tracks bodies circling the Earth and models their trajectories to avoid crashes.
“I have looked at the data going back to May 2019 when Starlink was first launched to understand the burden of these megaconstellations,” Lewis told Space.
“Since then, the number of encounters picked up by the Socrates database has more than doubled and now we are in a situation where Starlink accounts for half of all encounters.”
Once Starlink launches its full 12,000-strong satellite network, it will be involved in 90 per cent of all close approaches, it is estimated. Currently there are only 1,700 in space. SpaceX did not respond to The Independent’s request for comment by time of publication.
OneWeb, by comparison, currently has 250 satellites and passes another operators’ satellite 80 times per week. The two companies experienced such a problem in April 2021, when it was reported that a SpaceX satellite came within 60 meters of a OneWeb craft, with complaints over Starlink’s ability to move out of the way.
However, SpaceX later claimed this was not the case – stating that “the probability of collision never exceeded the threshold for a manoeuvre, and the satellites would not have collided even if no manoeuvre had been conducted”.
As well as satellites, there are approximately 228 million pieces of space debris around the globe.
An infamous study by Nasa scientist Donald Kessler in 1978 warned that, if two large objects collided, the domino effect caused by the material breaking apart, colliding into other material, and breaking again, could create an impenetrable layer of debris that would make terrestrial space launches impossible.
“This problem is really getting out of control,” Siemak Hesar, CEO and co-founder of commercial autonomous space traffic management system Kayhan Space, told Space.
“The processes that are currently in place are very manual, not scalable, and there is not enough information sharing between parties that might be affected if a collision happens.”
He estimates that, on average, a company managing 50 satellites would receive 300 conjunction alerts per week – about other satellites, and debris.
“In a situation when you are receiving alerts on a daily basis, you can’t manoeuvre for everything,” Lewis commented.
“The manoeuvres use propellant, the satellite cannot provide service. So there must be some threshold. But that means you are accepting a certain amount of risk. The problem is that at some point, you are likely to make a wrong decision.
“Starlink doesn’t publicise all the manoeuvres that they’re making, but it is believed that they are making a lot of small corrections and adjustments all the time. But that causes problems for everybody else because no one knows where the satellite is going to be and what it is going to do in the next few days.”
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