Just 60 years ago, there were no man-made objects above the planet Earth. Now, there are nearly 500,000 objects circling over Earth in various orbits. These include debris, inactive, and active satellites.
The tiny Sputnik, which means "satellite" or "fellow traveler" in Russian, was the first man-made satellite to be launched into Earth's orbit on Oct. 4, 1957, and it changed the course of human history.
This handout October 1957 NASA image shows a technician putting the finishing touches on Sputnik 1, the first artificial satellite. Photo from NASA.
The 58cm diameter, 83.6kg metallic orb, with four antennae that transmitted radio pulses, that was launched by the Soviet Union heralded the space race between the USSR and the US - ushering in an era of scientific advances, not only in military, but also in communications and navigation technologies.
There are approximately 1,500 active satellites currently orbiting the Earth. Modern society is heavily dependent on satellite technology, which is used for television and radio broadcasting, telephone calls, GPS navigation, mapping, weather forecasting, and other functions.
A map of currently tracked satellite objects. Photo courtesy of Wikimedia Commons.
Class of satellite orbit
|Class||Altitude||Orbital period||Common usage|
|Low Earth Orbit||80km - 1,700km||2 hrs||Communications, Earth observation, development (International Space Station, Hubble Space Telescope)|
|Medium Earth Orbit||1,700km - 35,700km||2 - 24 hrs||Navigation (GPS, GLONASS, Galileo)|
|Geosynchronous Orbit||35,700km||24 hrs||Broadcast, Weather|
|Elliptical Orbit||Variable||Variable||Communications (Sirius Satellite Radio)|
The Hubble Space Telescope in orbit. Photo from NASA.
The US share of satellites
US government and private entities own over 40 percent of all satellites currently in orbit. Most operational satellites currently in orbit are for used for communications, Earth observation, technology development, navigation, and space science.
They have lifetimes ranging from months to 30-plus years after launch.