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Satellite tower operators are constantly forced to move their satellites due to encounters with other spacecraft and space debris. And thanks to EspaceX Starlink satellites, the number of these dangerous approaches will continue to grow, according to estimates based on the available data.
EspaceX star link Satellites alone participate in around 1,600 close encounters between two spacecraft each week, according to Hugh Lewis, head of the Astronautical Research Group at the University of Southampton, UK. kilometers) from each other.
Lewis, the leading European expert on space debris, makes regular estimates of the situation in orbit based on data from the Socrates database (Satellite Orbit-Coupling Reports which assess dangerous encounters in space). This tool, operated by Celestrack, provides information on the orbits of satellites and models their future trajectories to assess the risk of collision.
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Lewis posts regular updates on Twitter and has seen a disturbing trend in the data that reflects the rapid spread of the Starlink constellation.
“I looked at data going back to May 2019, when Starlink first launched to understand the burden of these massive stars,” Lewis told Space.com. “Since then, the number of encounters captured in Socrates’ database has more than doubled, and we are now in a position where Starlink accounts for half of all encounters.”
The current 1,600 close passes include those between two Starlink satellites. With the exception of these encounters, Starlink satellites approach spacecraft from other operators 500 times a week.
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In the July update of the links that include #Starlink & #OneWeb as predicted by #SOCRATES (https://t.co/CjUGwoALuU), we can see the continued (exponential) increase in closing hours on August 2 2021
In comparison, Starlink competitor OneWeb, which currently flies more than 250 satellites, shares 80 close passes with other operators’ satellites each week, according to Lewis data.
The situation can only get worse. Only 1,700 satellites of a projected constellation of tens of thousands have been put into orbit to date. Lewis calculates that once SpaceX launches all 12,000 satellites of its first generation, Starlink satellites will participate in 90% of all close approaches.
And another for @ cosmos4u: Coupling counted on August 3, 2021
risk of collision
Simak Heiser, CEO and co-founder of Keihan Space Company, based in Boulder, Colorado, confirms this trend. His company, which is developing a commercial stand-alone space traffic management system, estimates that on average, an operator operating around 50 satellites will receive up to 300 official pairing alerts per week. These alerts include encounters with other satellites as well as debris. Of these 300 alerts, up to ten operators will have to be executed Cancellation of maneuversHisar told Space.com.
Kayhan Space bases its estimates on data provided by American Space Control Network. This network of radar and telescopes, operated by the US Space Force, closely monitors approximately 30,000 living and non-existent satellites and debris up to 10 cm (4 inches) and provides the most accurate location data for objects in orbit.
Hesar added that the size of this catalog is expected to increase tenfold in the near future, partly due to the growth of massive stars, such as Starlink, and partly as sensors improve and allow object detection. smaller. The more items there are in the catalog, the more dangerous the close encounters are.
“This problem is really out of control,” Hisar said. “The processes currently in place are very manual, non-scalable, and there is not enough information sharing between the parties that would be affected in the event of a collision.”
Compare the problem of grounding to that of driving on a freeway not knowing that there was an accident in front of you a few miles away. If two spacecraft collide in orbit, the cloud of debris generated by the crash will threaten other satellites traveling in the same area.
“You want to have this situational awareness of the other actors flying in the neighborhood,” Hisar said.
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Bad Decision
Despite concerns, only three confirmed orbital collisions have occurred so far. Earlier this week, astrophysicist and satellite tracker Jonathan McDowell, based at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, found evidence in Space-Track data that a Chinese weather satellite Ions 1-02, which disintegrated in March this year, has already been hit by space debris.
The worst known space collision in history In February 2009, the American communications satellite Iridium 33 and the late Russian military satellite Kosmos 2251 crashed at an altitude of 789 kilometers. The accident resulted in more than 1,000 pieces of debris larger than 4 inches (10 cm). Several of these fragments were subsequently involved in other orbital accidents.
Lewis is concerned that as the number of close passes increases, the risk of operators making the wrong decision at some point will also increase. Avoidance maneuvers cost fuel, time and effort. Therefore, operators always carefully assess these risks. However, deciding not to perform an evasive maneuver after an alert, such as the one issued by Iridium in 2009, could disrupt the tropical environment for years and decades.
“If you get alerts on a daily basis, you can’t maneuver everything,” Lewis said. “The maneuvers use thrusters and the satellite cannot provide service. So there must be some limit. But it does mean that you accept a certain level of risk. The problem is, at some point you will likely make the wrong decision.
Hisar said doubts about the location of the satellites and debris remain high. For operating satellites, the error can be as high as 330 feet (100 meters). In the case of debris, the uncertainty as to its exact location can be on the order of a mile or more.
“This body could be anywhere in this kilometer-long bubble,” Hisar said. “At this point, and for the foreseeable future, avoidance is our best recourse. People who say ‘I’m going to take a risk’, IMHO, are irresponsible. “
Starlink monopoly
Lewis is concerned about the growing influence of one actor – Starlink – on the safety of orbital operations. Especially, he says, when the spaceflight company has only recently entered the world of satellite operations.
“We trust one company to do the right thing,” Lewis said. “We’re in a position where Starlink will involve most of the maneuvering that we see. They used to be a launch provider, and now they’re the biggest satellite operator in the world, but they’ve only been doing that for two years, so there’s some inexperience. “
SpaceX relies on an independent collision avoidance system to keep its fleet away from other spacecraft. This, however, can sometimes lead to more problems. According to Lewis, spontaneous orbital adjustments change the predicted trajectory, making collision predictions more complex.
“Starlink doesn’t publish every maneuver they make, but it is believed that they do a lot of little fixes and adjustments all the time,” Lewis said. “But it causes problems for everyone because nobody knows where the satellite will be and what it will do in the next few days.”
Follow Teresa Pultarova on Twitter @TerezaPultarova. follow us On Twitter @Spacedotcom and on Facebook.
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