Stellar astronomer and software developer Dr Meredith Rawls is a stellar astronomer and software developer working as a research scientist with the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) group at the University of Washington. As a software developer, Rawls is involved in developing algorithms that can identify objects in telescope data that have changed, and characterize them accordingly. Her work also entails researching how low-Earth orbit satellites affect astronomy and what satellite operator companies can do to reduce their impact on the night sky. How do low-Earth orbit satellites pose a problem for ground-based astronomy? The main thing is there are so many of them that are currently being launched and planned to be launched and they reflect sunlight so they can be really bright. The brightness actually surprised some of the satellite operators, they had not anticipated how bright their satellites were actually going to be. Astronomers were used to sometimes seeing satellites, but now it's an order of magnitude more and they're going to be showing up very commonly in observations from ground-based telescopes. Are all aspects of astronomy affected? I tend to be very biased towards the ground-based optical astronomy because that's our human experience with the night sky and they're the main kind of observations that I was trained in as a student. But radio astronomy is maybe even going to be more severely impacted than optical astronomy. It's complicated. Radio astronomers have been competing for years for a frequency spectrum, they have this national and international relations about who gets what frequencies on the radio spectrum, for example your mobile phone service, your WiFi, any gadget that transmits has to have approval. Radio astronomers have fought long and hard to make their presence known and say "we need this chunk of the spectrum because that’s where Hydrogen emits, we can't change that", in the U.S. they go to lobbying meetings to make their voices heard, so there is already a presence of radio astronomers in some of these regulatory spaces. The issue with growing numbers of low-Earth orbit satellite constellations is that one of the main goals they have is to send down high amounts of data for internet access so they'll be constantly beaming down loud radio signals down to Earth so people can get their internet connection. This is potentially going to cover a large amount of ground. There are some things that they could do to try and lower the effects on radio astronomy, for example turning off their transmitters when they are over radio telescopes. But the reality is that if you have located a set of frequencies that you are going to use, physically these waves spill over the edges, you cannot have a sharp cut off, it's just not how waves work. So even with the best intended regulations controlling what frequencies are being used by satellite companies, it is going to have some pretty serious effects on radio astronomy. If low-Earth orbit satellites are problematic, should the companies just place the satellites higher? Actually that would be worse. It's a little complicated because you could think that maybe a lower orbit satellite would be brighter because it is closer, which is true but the trick is that it moves faster in a lower orbit because it has to not fall out of the sky. That means that when you are taking a picture it will move out of the way faster and the pixels won't linger long enough to make as bright of a streak in the image, which is better. So I was personally disappointed that OneWeb decided to keep their satellites at a higher altitude, whereas SpaceX have been more willing to keep their satellites at lower altitudes. Though space debris will become an even bigger problem at these lower altitudes as the lower the orbit, the more crowded it gets. Starlink collision risk SpaceX received additional backlash in September 2019, when the European Space Agency (ESA) announced that it had directed its Aeolus satellite to undertake evasive maneuvers and avoid crashing into "Starlink 44," one of the first 60 satellites in the megaconstellation. The agency took action after learning from the U.S. military that the probability of a collision was 1 in 1,000 — 10 times higher than ESA's threshold for conducting a collision-avoidance maneuver. In August 2021, Hugh Lewis, the head of the Astronautics Research Group at the University of Southampton, U.K. and Europe's leading space debris expert, told Space.com that Starlink satellites represent the single main sources of collision risk in low Earth orbit. According to computer models, at that time, Starlink satellites were involved every week in about 1,600 encounters between two spacecraft closer than 0.6 miles (1 kilometer). That's about 50% of all such incidents. This number rises with every new batch of satellites launched into space. By the time Starlink deploys all 12,000 satellites of its first-generation constellation it could reach 90%, Lewis said. Lewis also expressed concerns that Starlink's operator SpaceX, a newcomer into the satellite business, is now the single most dominant player in the field whose decisions can affect the safety of all operations in low Earth orbit. End of lifespan deorbiting procedure SpaceX plans to refresh the Starlink megaconstellation every five years with newer technology. At the end of their service, the old satellites will be steered into Earth's atmosphere where they will burn up. That is certainly commendable when it comes to space debris prevention, however, there is another problem. The vast amount of satellites that will be burning in the otherwise pristine upper layers of the atmosphere could alter the atmospheric chemistry and have unforeseen consequences for life on the planet. In a paper published in May 2021 in the journal Scientific Reports, Canadian researcher Aaron Boley said the aluminum the satellites are made of will produce aluminum oxide, also known as alumina, during burn-up. He warned that alumina is known to cause ozone depletion and could also alter the atmosphere's ability to reflect heat. "Alumina reflects light at certain wavelengths and if you dump enough alumina into the atmosphere, you are going to create scattering and eventually change the albedo of the planet," Boley told Space.com. That could lead to an out-of-control geoengineering experiment, a change in the Earth's climate balance. The effects of such alternations are currently unknown. Karen Rosenlof, an atmospheric chemistry expert at the National Oceanic and Atmospheric Administration (NOAA), told Space.com she too was concerned about the effects of the particles from the burning satellites in the atmosphere. Rosenlof has expertise in modeling the effects of geoengineering interventions. David Fahey, the Director of NOAA's Chemical Sciences Laboratory, and Martin Ross, a physics and meteorology scientist at the Aerospace Corporation, both told Space.com that more research is urgently needed to understand the effects of burning increasing amounts of satellites in the atmosphere. The problem, the scientists said, is that in those high layers of the atmosphere, the particles are likely going to stay forever. Boley said that while the number of satellites burning in the atmosphere will be considerably smaller than the number of meteorites, the chemical composition of the artificial objects is different, thus the presence of the products of their burning is something scientists know nothing about. "We have 54 tonnes (60 tons) of meteoroid material coming in every day," Boley said. "With the first generation of Starlink, we can expect about 2 tonnes (2.2 tons) of dead satellites reentering Earth's atmosphere daily. But meteoroids are mostly rock, which is made of oxygen, magnesium and silicon. These satellites are mostly aluminum, which the meteoroids contain only in a very small amount, about 1%." As the accumulation of those particles would increase over time, so would the intensity of the effects. It thus cannot be ruled out that over decades the pollution from burning megaconstellation satellites could lead to changes on a scale akin to what we are currently experiencing with fossil-fuel-induced climate change. "Humans are exceptionally good at underestimating our ability to change the environment," said Boley. "There is this perception that there is no way that we can dump enough plastic into the ocean to make a difference. There is no way we can dump enough carbon into the atmosphere to make a difference. But here we are. We have a plastic pollution problem with the ocean, we have climate change ongoing as a result of our actions and our changing of the composition of the atmosphere and we are poised to make the same type of mistake by our use of space." Starlink did not respond to Space.com requests for comment. A Starlink satellite's lifespan can also be cut short by powerful geomagnetic storms. On Feb. 3, 2022, a SpaceX Falcon 9 rocket made a routine and successful launch of 49 Starlink satellites from NASA's Kennedy Space Center in Florida. But only a day later, a geomagnetic storm above Earth pushed up the density of the atmosphere, increasing the drag on the satellites and dooming the bulk of them to an early death. "Preliminary analysis show the increased drag at the low altitudes prevented the satellites from leaving safe mode to begin orbit-raising maneuvers, and up to 40 of the satellites will reenter or already have reentered the Earth's atmosphere," SpaceX wrote in an update on Feb. 8, 2022.