In Feb. 2009, the U.S. communications satellite Iridium 33 and the Russian military satellite Cosmos 2251 collided about 790 kilometers above Earth. It was the first large-scale case of a collision between satellites, and more than 2,500 fragments were created and left in low Earth orbit after the incident. Since then, the number of satellites has surged, making collision avoidance and space traffic management new challenges.
The European Southern Observatory (ESO) said on the 3rd that about 15,000 satellites are currently operating in Earth orbit, but when combining all planned mega-constellations by countries and corporations, the total could potentially reach 1.7 million. The researchers noted that this growth could worsen not only the environment for astronomical observations but also congestion in low Earth orbit.
The biggest driver of satellite growth now is low Earth orbit internet service. Because low Earth orbit is closer to the ground, it offers short communication latency, and global corporations are competing to use it. SpaceX's Starlink and Amazon, among others, are pushing plans to build large satellite networks.
As satellites cluster in low Earth orbit, managing collision risk is becoming a practical task. In low orbits, satellites travel at several kilometers per second, and even a collision with small debris can cause catastrophic damage.
The European Space Agency (ESA) explains that 1-centimeter space debris can disable an operating spacecraft, and debris 10 centimeters or larger can cause damage that completely destroys a satellite upon impact. It also counts the possibility of "cascade fragmentation," in which debris from a satellite collision triggers additional collisions, as a major risk to the space environment.
In actual operations, the number of maneuvers to avoid collisions is rising rapidly. According to materials SpaceX submitted to the U.S. Federal Communications Commission (FCC) in Jul., Starlink satellites carried out about 350,000 collision-avoidance maneuvers over the past year. These are orbit adjustments made to reduce the chance of close approaches with other satellites or space objects.
The impact of satellite growth is not limited to the space industry. Astronomers worry that low Earth orbit satellites can degrade telescope observation data.
Telescopes collect light for long periods to observe faint objects such as distant galaxies and asteroids. When a satellite crosses the field of view during this process, it leaves a bright streak in the image. Some can be removed with correction software, but as the number of satellites increases, so does the loss of observational data. Olivier Hainaut, an ESO researcher, said, "The trail of a single satellite may be a small problem, but as the number grows, it becomes a big problem."
In radio astronomy, there are also concerns about interference from the rise in satellites. An international team including the Max Planck Institute for Radio Astronomy said in 2023 that observations of Starlink satellites with radio telescopes confirmed "unintentional electromagnetic emissions" from onboard electronics. The researchers analyzed that if mega-constellations expand, they could affect radio astronomical observations.
The American Astronomical Society (AAS) also warned that the growth of mega-constellations could worsen congestion in radio frequencies, and that existing ground-based methods to mitigate radio interference may have limits. The AAS suggests that satellite operators and the astronomy community cooperate in advance and devise measures from the satellite design stage to reduce observational impacts.
Because of this, the international community sees establishing systems to manage the satellite industry as a more important task than expansion itself. Aarti Holla-Maini, Director General of the United Nations Office for Outer Space Affairs (UNOOSA), said, "We can no longer delay space traffic coordination," adding, "For space safety, information sharing between public and private operators is necessary."
More recently, the expansion of the artificial intelligence (AI) industry is emerging as a new variable driving satellite growth. The idea of a "space data center" has surfaced, aiming to build data-processing facilities in space to ease the burden on ground data centers that consume massive amounts of electricity.
In Feb., SpaceX submitted to the U.S. Federal Communications Commission (FCC) a plan to build a solar-powered space data center satellite network. The plan envisions up to 1 million satellites, but whether launches and operations will proceed depends on regulatory approval and technical review.