Satellites can actually change the way astronomers study the sky at night. Megaconstellations in the low Earth orbit – like the Starlink network can have a huge impact on this matter. SpaceX has already launched 600 Starlink satellites, and they have in plan to launch 30.000 more. Amazon wants to launch 3.200 broadband satellites as well – part of Project Kuiper.
As of now, about 2,500 operational satellites are circling Earth, and we have launched more than 10.000 objects ever since 1957.
The impact that they have on the night sky actually depends on numerous factors, including the ability to remove satellite trails from their datasets, the brightness, and the altitude of the satellites. Satellite trails will represent a problem for telescopes that view the sky in infrared and visible light.
The satellites will remain illuminated by the sun, so observing programs will also be affected.
Let’s take a clear example. A large constellation that’s orbiting 750 miles – that’s 1200 km – OneWeb’s 74 broadband satellites “will be visible all night during summer and significant fractions of the night during winter, fall, and spring, and will have negative impacts on nearly all observational programs.” OneWeb wants to launch at least 650 satellites, but it’s not sure if the constellation will get that big.
Constellations that orbit less than 370 miles – that’s 600 km – above Earth will not have the same impact, and Starlink falls into this category. These satellites fly at about 340 miles (550 km).
It is recommended to launch fewer or even no LEO megaconstellations: this “is the only option identified that can achieve zero impact.”