Are Satellites in the sky or are they in space?

Question

Are Satellites in the sky or are they in space?

In: Planetary Science

Answer 1

“Space” is generally accepted to begin 100 km above sea level, but this is an arbitrary boundary. There is no hard edge between the atmosphere and outer space.

However, stable orbit is not generally possible anywhere near that altitude because of atmospheric drag. A Japanese program creatively called the “Super Low Altitude Test Satellite” (SLATS) was launched in 2017 to test a so-called “very low Earth orbit” (VLEO). It was able to orbit at 167.4 km for a week, which was recognized by Guinness as the world record lowest altitude satellite. It was decommissioned in 2019.

In contrast, the ISS orbits around 420 km, which is considered “low Earth orbit” (LEO). Most communications satellites are in geostationary orbit, which is about 36,000 km.