Space is immense. But are parts of space at risk of becoming saturated with internet satellites and cosmic junk?
As the number of satellites launched and proposed for low Earth orbit continues to grow, there is growing concern for government agencies, astronomers and other stakeholders.
At the heart of the concerns are the increased risk of collisions creating debris fields capable of knocking out nearby satellites; bright reflections that harm scientific astronomy and change the night sky; air pollution from thousands of satellites burning up in orbit every few years; and interference with radio signals that block access to rival satellite equipment, including those of sovereign nations.
All this is known as carrying capacity. “Some say we’re not even close to carrying capacity, while others say authorized groups already exceed that capacity. Which one is correct?” says Mark Dankberg, co-founder and CEO of Viasat.
Eight years ago there were about 1,300 satellites in orbit. Today there are an estimated 7,500 and growing.
Applications for more than 60,000 new satellites are pending with the US Federal Communications Commission.
These new satellites aim to enter orbits where debris is already whizzing by at 17,000 mph. According to the European Space Agency, more than 36,000 objects with a diameter equal to or greater than a grapefruit orbit Earth. These include millions of fast-moving particles ranging in size from a pea to a grapefruit. And about 130 million objects are smaller than a pea.
SpaceX’s Starlink satellites, which have object-avoidance propulsion, have performed an increasing number of evasion maneuvers, according to Hugh Lewis, a professor of aeronautics at the University of Southampton in the United Kingdom.
In an email to the Union-Tribune, Lewis estimated that Starlink satellites performed 5,340 offensive maneuvers in March alone, though it is difficult to know why these were dodged.
Jonathan McDowell, a renowned astrophysicist at the Harvard-Smithsonian Center for Astrophysics, said: “The closer you get, the more evolved the maneuvers are, and the more players there are – not just the number of satellites, but the number of different satellites owned.” organizations—then you get to a point where conflict becomes pretty much inevitable.”
The collision probably isn’t catastrophic. “But when you have one every two years, the amount of space debris adds up exponentially and you get to a point where low Earth orbit becomes really unusable,” explains McDowell. “We haven’t reached that point yet, but the risk continues to rise.”
SpaceX did not respond to a request for comment. But in an FCC filing, the company said it uses a conservative trigger threshold that’s more sensitive than the industry standard. The system is automated.
It also said it has developed collision avoidance agreements with rival satellite operators to “facilitate physical coordination”.
The company said its first-generation satellites will perform an average of three collision avoidance maneuvers every six months through 2022, many of them to avoid debris from the Russian anti-satellite missile display that caused satellites removed from Russia in November. One of them was destroyed. 2021.
Nevertheless, China informed the United Nations in December 2021 that its space station had two close encounters with Starlink satellites and carried out maneuvers.
Because its satellites have yaw propulsion, the FCC deemed Starlink’s first generation of 4,400 satellites not to present a collision hazard.
When Starlink applied for approval for 30,000 second-generation satellites — each much larger than the first generation — regulators blocked it.
Currently, SpaceX has received authorization for 7,500 second generation satellites. One concern is the effect of the Sun’s reflections on telescopes used to track asteroids or for Earth-observing missions that measure weather.
Each of Starlink’s first-generation satellites weighs 600 pounds and measures about 280 square feet in cross section, according to FCC filings. Each second-generation satellite weighs 4,400 pounds and covers 2,950 square feet.
“If you look at what happens with low-Earth orbit satellites, before there were a large number of small satellites,” explains Dankberg, ViaSat’s CEO. “What’s happening now is a large number of large satellites.”
SpaceX has said it is working with the National Science Foundation to reduce the brightness of its satellites.
“I don’t care about a few shiny satellites,” McDowell said. “They’re annoying, but not existential. But when you get to 30,000 or 50,000 — those kinds of numbers — then it starts to become a really big problem for astronomy because almost every picture taken will have a satellite.