Environmental impact of satellites: from the Vera C. Rubin Observatory to SpaceX, Starlink, and other telecommunications satellites
Satellites are increasingly a global-communications lifeline, allowing people in remote areas, even war zones, to make phone calls and get online without the need for ground-based infrastructure. Services such as SpaceX’s Starlink, by far the largest of the networks of telecommunications satellites in low Earth orbit, have been booming during the past decade. Between 2017 and 2022, companies requested access to the radiofrequency spectrum for more than one million satellites.
It comes at a cost, and there are mounting concerns about safety. Most of the time, satellites are single-use products with a lifespan of less than 15 years. Moreover, space debris is a growing problem, as physicists Richard O. Ocaya at the University of the Free State in Bloemfontein, South Africa and Thembinkosi D. Malevu at North-West University, Potchefstroom, South Africa, describe in a Comment article. There are questions regarding whether or not humans could or should put satellite transmitters in the environment.
The Vera C. Rubin Observatory is located on a mountain inChile and will begin surveying the universe with the biggest camera ever built. It will give a map of the southern sky every three nights, filled with stars, asteroids, and satellites.
Work towards this is under way, but needs to speed up. Three years ago, the IAU established a centre in Paris for protection of dark and quiet skies. It is a hub for scientific, policy, industry and community discussions about satellite swarms, and it has put forward common-sense recommendations that are already being adopted. France updated its national space law last year, which will make French satellites less bright.
Raising awareness is the first step. Finance is another. The centre is run on a shoestring of donations and free time. Funders should step up with more support, as the US National Science Foundation did last year with a US$750,000 grant to the IAU to develop software tools that predict when satellites will appear in telescopes’ fields of view.
Those who build and fly satellites have a role to play. As the largest operator with over 7,000 satellites, SpaceX has led the way in working with astronomer to reduce the impact on Rubin and other observatories. Other companies should follow SpaceX’s lead. This could include releasing more information on satellite specifications and the frequencies of their radio transmissions, as well as real-time locations of the craft. Much of this information is commercially sensitive, but at least some could be shared in ways that would still be useful to astronomers, with proprietary details redacted.
The discussions about the future of satellite swarms need to be included in broader conversations about the future of space. That includes integrating perspectives from Indigenous peoples, many of whom have important connections with the night sky, but who have long been marginalized from decision-making and economic power in outer space.
The number of working satellites has soared in the past five years to around 11,000, mostly because of constellations of orbiters that provide Internet connectivity around the globe (see ‘Satellite surge’). Just one company, SpaceX in Hawthorne, California, has more than 7,000 operational Starlink satellites, all launched since 2019; OneWeb, a space communications company in London, has more than 630 satellites in its constellation. On paper, tens to hundreds of thousands more are planned from a variety of companies and nations, although probably not all of these will be launched1.
Satellites play a crucial part in connecting people, including bringing Internet to remote communities and emergency responders. The satellites can cause problems for scientists because of the interference with ground-based astronomical observations and bright streaks on images. Adding pollution to the atmosphere is one of the threats caused by the satellite boom.
The centre has a tool called SatChecker, which draws information from a public database of satellite orbits, as well as from companies and observers that track objects in space. Astronomers can use SatChecker to confirm what satellite is passing overhead during their observations. The tool is imperfect, atmospheric drag and intentional maneuvers can affect a satellite’s position and the public database doesn’t always reflect latest information. Uncertainty of its position was so great at times that it was hard to know whether the blueWalker 3 satellite would be in their view at night.
The problem was mitigated by the early steps taken by the company. Working with Rubin astronomers, the company tested changes to the design and positions of Starlinks to try to keep their brightness beneath a target threshold. Amazon, the retail and technology giant based in Seattle, Washington, is also testing mitigations on prototype satellites for its planned Kuiper constellation. Such changes reduce, but don’t eliminate, the problem.
SCORE: Status and Prospects for a High-Quality Database of Optical and Near-Infrared Observations
The database is useful because of it being one of only a few that have data free of charge. Langbroek has added some entries to SCORE, including a NASA solar sail that changes in brightness as it plummets through space. Going forwards, he says, SCORE will be most useful if a lot of astronomers contribute high-quality observations to the database, thereby building up a resource over time.