It acts as a Bragg mirror
Astronomers will now see fewer SpaceX satellites when observing the sky. After years of scientists complaining about the high reflectivity of the company’s constellation of Internet satellites, SpaceX has begun using a new “mirror film” that diffuses light from Earth.
Last week, SpaceX launched 22 new Starlink V2 satellites on a Falcon 9 rocket, demonstrating the new mirror coating for the first time. A previously published video shows a highly reflective dielectric mirror film covering satellites. It seems counterintuitive that adding a mirror coating to satellites would make them less visible from the ground, but that’s exactly what Starlink claims.
SpaceX unveils ‘mirror film’ to hide Starlink satellites from astronomers
SpaceX says it has been working for the past few years on this film, which acts as a Bragg mirror, also known as a distributed Bragg reflector. It consists of several layers of plastic with different refractive indices. This creates interference patterns that scatter light but transmit radio waves. SpaceX also coated parts of the satellites with low-reflective black paint to absorb light.
SpaceX designed the Starlink satellites to be cheap and easy to replace, but the more visible versions to astronomers will remain in orbit for years. Some existing satellites have “canopies” to reduce reflectivity, but SpaceX was never happy with this solution because it increased atmospheric drag after launch.
Starlink is currently the only satellite megaconstellation, but other companies such as Amazon are planning to launch their own versions.
