The technical definition of a satellite isn’t something widely known. A satellite is anything that orbits a nearby planet. It doesn’t matter if the satellite is natural (i.e. the moon) or manmade. Regarding the latter, the Earth has many satellites in orbit apart from the moon, including everything since the beginning of the space age 59 years ago, with the launch of the Soviet Union’s Sputnik 1.
Up in the Heavens
Lots of uses exist for the satellites currently orbiting Earth. Many of them are vital to the function of navigation systems. Apart from allowing the triangulation of one’s position anywhere on Earth, satellites and their movement patterns are also useful for designing equipment like GNSS signal simulators. Or perhaps they’re used for defense systems or the internet.
Either way, the modern technology relies on manmade satellites in orbit, one way or another. The start of the space age sprung a massive amount of satellite launches. According to NASA, there are over 1,000 operational satellites in orbit today, about half of which were launched by the US.
As for an approximation of all satellites in orbit, whether operational or not, it’s a larger number: 4,256. That’s according to the United Nations Office for Outer Space Affairs (UNOOSA). The number increased by 4.39 percent last year compared to 2015. Satellite launches seem to be quite common because these devices can’t last forever. Fifteen years is an accepted (and general) time frame for larger ones, while a minimum of 3 months is expected for smaller satellites.
Manmade satellites do not circle the Earth unlike their natural counterpart, the moon. Artificial satellites remain fixed at a particular position in the planet’s orbit. This makes them perfect for specific applications. A rundown of the uses of such satellites yields familiar terms: communications, Earth observation, navigation and global positioning, and technology demonstrations.
The satellites occupy three Earth orbit levels: low-Earth, medium-Earth, and geostationary levels. Low-Earth orbits are just several hundred kilometers from the planet’s surface. This is where many satellites for planetary observation reside, such as the International Space Station (ISS). Going higher, you find the satellites intended for GPS at the medium-Earth orbit, with the more advanced ones for astronomical application in geostationary orbit.