The word satellite originally meant 'co-traveler' or 'traveling companion', and was first attributed to natural bodies orbiting planets such as the Moon, for example, which is Earth's satellite. Currently, the word satellite is mostly used to describe man-made instruments orbiting the Earth, while moons circling planets are called natural satellites. The vast majority of the satellites are put into the orbit with the help of rockets and are designed to carry out military missions, weather forecasts, scientific studies or telecommunication transmission.
Incredible as it may seem, the first artificial satellite put into Earth's orbit was not an American one, but a soviet satellite, and had the role of studying the upper layers of the atmosphere. At first, the U.S. scientists thought that the announcement made by the Russians was a joke; however, when they detected the radio signals sent back to Earth by Sputnik 1, they realized that they had greatly underestimated the scientific community based in Russia. The threat posed by such an event was further amplified
by speculations that Sputnik might be used to release a nuclear warhead on U.S. soil. However, the Soviet Union was more interested in humiliating the U.S. by making scientific advances rather than starting a new war.
Satellites are kept into orbit by the gravitational pull exerted by the object it circles. You might think that beyond Earth's atmosphere, such as the location of the International Space Station, gravitational pull is close to zero. Think again, gravity is everywhere in space and it's just weaker. For example, the gravitational pull exerted on the ISS is 90 percent of that experienced on the surface of the planet. Why doesn't the ISS fall to the ground you ask? Well, in fact, it does fall to Earth, but not in a vertical manner; the ISS falls towards the Earth in a side motion, at speeds exceeding 7.7 kilometers per second, which allows it to orbit the planet in the lowest orbit possible, meaning an altitude of about 390 kilometers about the surface.
Due to the lack of air outside the Earth's atmosphere, the ISS, similar to the satellites in our planet's orbit, does not lose momentum and only requires the gravitational attraction to keep it moving, in order to maintain its trajectory. However, some energy is lost through other means, fact that eventually triggers a process that slows the vehicle decaying its orbit, and determines it to fall further into an even lower orbit, until it encounters the atmosphere that will inevitably destroy the object. In order to maintain a stable orbit around the Earth, any object must travel at a speed of at least 27,800 kilometers per hour, in which condition its falling trajectory back to the surface of the planet accurately describes the curvature of the Earth, thus the object will forever fall around the planet rather than towards it.
Sputnik 1, the first ever satellite launched into space, had an orbit at an altitude of about 160 kilometers about the Earth's surface and made a complete trip around the planet every 96 minutes, unlike the Moon which orbits Earth from a distance of 386,000 kilometers and makes a complete rotation every 28 days.
Other satellites like those used for weather forecasting, for example, are usually placed in orbits above the equator, at altitudes as high as 36,000 kilometers, which determines them to make a complete rotation of the planet every 24 hours, while geostationary satellites can be positioned in such way that they rotate at the same time with the Earth, and seem to have a stationary position in relation to the surface of the planet.
Geosyncron satellites, as they are known, are mostly used for telecommunication purposes, to send television and communications transmissions towards the surface of the Earth.
|
No user comments yet.
Be the first to express your opinion using the form below!
