by 
The ever-growing satellite population has created challenges for ground-based astronomy, but new research shows that space-based telescopes such as Hubble are also suffering.
Low Earth Orbit (LEO) satellites orbit the Earth once every 90 minutes. Factor in the thousands upon thousands of satellites currently operating in orbit, and you can quickly spot the problem with ground-based astronomy. Constellations such as Starlink and OneWeb greatly exacerbate the problem, producing annoying streaks in astronomical images. That is how serious the situation is for the researchers declared satellite constellations an “existential threat to astronomy.”
Space-based astronomy might seem like an obvious solution, with SpaceX founder Elon Musk suggesting as much in May 2019 chirping. Research published this week in Natural astronomy suggests otherwise, showing the extent to which the Hubble Space Telescope is being affected by these burgeoning satellite swarms.
The research, led by Sandor Kruk of the Max Planck Institute for Extraterrestrial Physics in Germany, found that 3.7% of Hubble images taken from 2009 to 2020 were tainted by satellite streaks. In 2021, this figure had risen to 5.9%. There were 1,562 Starlink and 320 OneWeb satellites in orbit at the time, which “increased the population of satellites close to Hubble’s orbit,” the researchers write.
G/O Media may receive a commission
For the study, the researchers looked at more than 100,000 individual Hubble images contributed by over 10,000 citizen scientists working with Hubble Asteroid Hunter project. A deep learning algorithm was trained to detect images marred by satellite streaks and ignore similar trail-like features caused by natural phenomena, such as asteroids, gravitational lensing and cosmic rays.
Data for this analysis stopped in 2021, but it is now two years later, and with so many more satellites currently working in orbit, the problem is undoubtedly much worse. Moreover, as Kruk and colleagues gloomily conclude: “With the increasing number of artificial satellites currently planned, the proportion of Hubble Space Telescope images traversed by satellites will increase over the next decade and will need further close study and monitoring.”
The 33-year-old Hubble may be long in the tooth, but it still performs critically scientific work, whether hunting for asteroids, monitoring NASA experimentsor simply staring into the sky. That satellite swarms have a detrimental effect on space-based astronomy is obviously not good.
“We are going to live with this problem. And astronomy will be affected,” Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, told New York Times citing the new study. “There will be science that cannot be done. It will be science that is significantly more expensive to do. There will be things we miss.”
Astronomers, in an attempt to prevent the situation from getting worse, have organized and agitated accordingly. In the latest development, a international cooperation asked the UN for helpand asks it to set up an expert group on the matter.
Meanwhile, astronomers are not completely helpless, as they can use various computing and filtering techniques to identify and potentially save spoiled images. And as NASA told the New York Times, “most affected images are still usable.” That said, the additional time and cost of astronomical research is hardly ideal.
Astronomers are also asking satellite operators to do their part, such as making the satellites less reflective. In response to such requests, SpaceX has experimented with some mitigation techniques for Starlink, such as using dark paint to absorb sunlight. Unfortunately, this particular “restriction was less effective than desired,” according to SpaceX. Other approaches, namely a visor to block reflective sunlight and orientation adjustments to minimize the surface, have proven to be “highly effective”, claims the company. SpaceX is also experimenting with “dielectric mirror film,” which directs light away from Earth.
Hubble currently operates about 540 kilometers above the surface, which is about 10 kilometers lower than some of the highest Starlink satellites. One solution could be to significantly raise Hubble’s orbit, which has shrunk dramatically over the decades. NASA and SpaceX are making a plan to find out if such a thing is possible.
As an aside, the recently deployed Webb Space Telescope is immune to satellite streaks, as it works 932,000 miles (1.5 million km) away in the second Lagrange point.
Raising Hubble’s orbit may work, but it will serve as little consolation for the other telescopes in operation in low Earth orbit and those currently under development, such as China’s upcoming Xuntian Space Telescope. This is still a problem in search of a solution.
