Manmade objects orbiting Earth are vast, from those used to observe our planet itself to others that study Mars, asteroids or even distant stars.
Satellites remain in orbit by using fuel to balance their tendency toward flight into space with Earth’s gravitational pull and maintain their velocity in orbit.
Satellites
From a distance, satellites resemble small boxy shapes with large antennas that resemble umbrellas. Inside this structure lies electronic systems designed to enable communication with people and objects on Earth.
Satellites carry all the technology and instruments required for specific missions. For instance, communication satellites need large antennas to transmit television and telephone signals while disaster monitoring satellites often include cameras capable of taking photographs from space of what lies below them.
When their satellites have finished their mission, the United Nations requires companies to remove them from orbit using either a harpoon to pick them up or lasers that heat it up, increasing atmospheric drag and leading it back towards Earth’s orbit.
Satellites play an invaluable role in businesses, governments and societies around the globe – yet most people remain unaware of this fact. According to the Union of Concerned Scientists’ Satellite Database there are approximately 8 261 functioning satellites orbiting Earth today (and many more that simply lie there unusably) but all of those shown above reside in low Earth orbit.
Bird’s-Eye View
Bird’s-eye view refers to an aerial perspective of Earth. This phrase can be used both figuratively and literally; some use it to refer to an overview or comprehensive assessment of an event or situation. Synonyms include aerial perspective, airplane view, fly on the wall view and great view.
Certain satellites orbit Earth in a solar-synchronous orbit, meaning that they remain over the same spot at all times of day and are therefore ideal for communications and surveillance.
Other spacecraft orbit the Earth from polar orbits, providing them with an unparalleled view of both our planet and its moons. Polar-orbiting satellites can assist us in understanding life on our planet as well as its nature within the universe, space radiation effects (particularly near-Earth radiation that may impact robotic and manned missions), space radiation risks to space travel as well as understanding our atmospheric composition better.
Orbital Velocity
As satellites travel farther around Earth, their required velocity to stay on course increases proportionately; this is because an object’s orbital velocity depends on both mass and the gravitational constant G.
At an appropriate orbital velocity, gravity exactly counterbalances satellite inertia by drawing it down towards Earth’s center. If its orbital velocity were lower than necessary, however, its inertia might lead it away into space and cause irreparable damage to our planet.
To remain at 22,223 miles (35,786 kilometers), a satellite needs to race around Earth every 24 hours in what’s known as geostationary orbit – an orbit used for communications and weather satellites. The speed required to achieve orbital velocity varies based on altitude; eventually however it will return into our atmosphere and burn up; but those launched at higher altitudes could continue orbiting for hundreds or even thousands of years!
Falling Objects
Gravity pulls objects down. In contrast, objects in orbit are accelerated at a specific rate by gravity – appearing to “float.” This figure shows how mass, size and shape do not impact acceleration during free fall; both astronaut and Space Shuttle share equal acceleration rates as they pass Earth.
There are currently thousands of satellites orbiting Earth. Why don’t they simply drop back down? Gravity tugs at them, yet due to being so high up there is only a very minimal amount of drag.
Satellites may be both natural, such as Earth’s moon, or manmade (such as the International Space Station). Both feature people living on them; stargazers and astronomers can observe these bodies through telescopes. A spacecraft is designed specifically for travelling through space; the first reusable one was launched into space in 1957.