SpaceX’s satellites are a huge headache for astronomers


Satellites are crucial to modern life – from weather forecasts to studying climate change and for communication. Now we are seeing the arrival of “megaconstellations” of satellites, in which multiple satellites function as a network to provide services such as global internet.
One company, SpaceX, has made the first significant steps in establishing a megaconstellation that will eventually comprise 12,000 satellites. In November 2019, it started launching its Starlink satellites in batches of 60, with the aim of providing a global broadband service. If priced correctly, this will especially benefit the 2.5 billion people who currently have no internet access. So far only about 800 satellites have been launched and it seems only the military has signed up to use them, but in 2021, SpaceX intends to have enough satellites and sufficient ground-based infrastructure to provide near-global coverage.


The impact of this will be that, no matter where someone is in the world, urban or rural, they will be able to get internet access. And it will be fast – up to a gigabit per second, with latencies from 25 to 35 milliseconds, according to the company – thanks to the fact that Starlink satellites will operate at a relatively low orbit of 550km.
Where SpaceX has led the way, others intend to follow. Blue Origin, founded by Jeff Bezos, plans its own megaconstellation of more than 3,000 satellites, called Kuiper. These will orbit between 590km and 630km above the Earth, and will also be used to provide broadband to those who are unable to access it terrestrially.
They also, however, have a less welcome impact. The satellites’ solar panels reflect sunlight, making them appear as fast moving spots of light across the sky. Indeed, many of us have already seen the Starlink satellites in space shortly after their launch, crossing the sky as long “trains”. This can be a problem for astronomers, who are already seeing their images “photobombed” by satellites, making them harder to analyse.
SpaceX has been engaging with this issue and taking steps to reduce the visible impact of its satellites by adding sunshades and altering their orientation so that they will be much harder to see with the naked eye.
It is not yet clear what mitigating measures Blue Origin will take.


Megaconstellations will bring huge benefits to people back down on Earth, especially those who are currently unable to play a full part in the online world due to lack of connectivity, but in 2021 we will also have to ensure that they operate in ways that don’t affect our view and our understanding of those other residents of the sky – the stars.
Lucie Green is professor of physics and a Royal Society university research fellow at the Mullard Space Science Laboratory, UCL

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