What is satellite?
Any heavenly body that moves around a planet s called a satellite. The Moon is a natural satellite of the Earth that orbits the Earth. Mars, Jupiter,Saturn,Uranus and Neptune have their own satellites too.
Beside moons of the planets, some other natural satellites are also moving around the Sun. These are asteroids, comets and meteoroids. Some of them can be seen from the Earth.
An asteroids is a piece of rock that orbits the Sun between Mars and Jupiter. The astronomers have discovered thousands of asteroids. Asteroids are made of rock, metals and minerals.
Most of the asteroids orbits the Sun between mars and Jupiter in a wide band. This band is called the asteroid belt. The asteroid belt is about 15 hundred thousand kilometers wide. Asteroid comes in all shapes and sizes.
Some asteroids have diameter up to 1,000 kilometers but some are very small in diameter.
Two asteroids are seen from the Earth without the help of a telescope. These are Ceres and Vesta. Ceres is the largest asteroid ever discovered. Its diameter is about 933 kilometers. Vesta is the half the size of Ceres.
A question may arise in our minds, “how were asteroids formed?” Some astronomers suggest that the asteroids are leftover matter from the time the planets were being formed. We can say that asteroids, may be the pieces of our solar system that never formed a planet.
Besides planets and asteroids some other objects also orbit the Sun. These are comets. A comet is a large ball of ice and dust that orbits the Sun. Comets move around the Sun in an elliptical path. They take a very long time to complete their one orbit around the Sun.
Comets probably come from the far, outer edges of the solar system. They are only seen when they come close to the Sun.
- A comet has three parts: a head, coma and a tail the head is made of ice, particles of rocks and gases. The heads is most comets are only a few kilometers wide.
- When a comets comes near the Sun, gases escape from its head due to the heat of the Sun. A large fuzzy, circular cloud around the head of a comet is called the coma.
- During orbiting near the Sun, a long tail of gases and dust particles is formed behind the comet. This tail can be millions of kilometers long. The tail of a comet points away from the Sun.
- Comets far away from the Sun bear no tail. Most of the time comets remain far away from the Sun.
A comet known as comet Halley has appeared in the sky many times. It appears after every 76 years. It was seen in 1986 for the last time. When can we expect to see Comet Halley againt?
Uncountable number of small heavenly bodies also orbit the Sun. These are called meteoroids. Meteoroid is a piece of rock or metal that orbits the Sun. Meteoroids are scattered in different orbits in space. Most of them are too small to be seen from the Earth.
Have you ever seen a shooting star bor fireball in the sky? In fact, it is no a star but a meteoroid entering the atmosphere of the Earth. Due to the friction of air, it gets fire.
A meteoroid when enters the atmosphere of our Earth. It is called a meteor. A meteor is a stray particle which comes from the asteroid belt and enters the atmosphere of the Earth. Due to the friction of air,the meteor gets fire and a trail of light is seen. Some people call them falling stars, shooting stars, or fireball. We can view 20 to 30 meteors on a clear night. But we have to move away from the glare of city lights.
Most meteors entering our atmosphere burn up 50 to 100 kilometres above the surface of the Earth. It adds tons of dust into our atmosphere everyday.
Sometimes a few big enough meteoroids do strike Earth’s surface. These are called meteorites. A meteorite is a meteor that strikes Earth’s surface.
There are many man-made satellites orbiting the Earth. These are called artificial satellites. Artificial satellites are very important for mankind. The first artificial satellite was sent by Russia in 1957. It was named Sputnik-1. Launching of this satellite opened new horizons for the Scientists. After a few years of launching Sputnik-1, Russia sent Yuri Gagarin, the first man into space. Since then, thousands of satellite have been sent into space.
Orbits of Artificial satellites:
Artificial satellites move around the Earth in different orbits. Some orbits are given here:
The orbit in which an artificial satellite completes its one orbit in the same time that the Earth takes to complete one spin,i.e.24 hours, is called geostationary orbit. A satellite in this orbit looks stationary from the Earth.
Polar orbit passes over the north and south poles of the Earth.so,satellites moving in this orbit can scan the whole Earth during their motion.
The scientific satellites move in eccentric orbit to measure magnetism and electric fields of the Earth.
Low Earth orbit:
This orbit is very close to the Earth. Low Earth orbit is used by space shuttles, space stations and the Hubble telescope.these satellites may orbit the very 90 minutes.
State receiving station:
A station on the Earth that receives massages from the satellites is called a satellite receiving station.
Launching of a satellite into space:
Launching of an artificial satellite into space is not very easy. This project requires a lot of money. The satellite is mounted on the top of a very high speed rocket. A rocket has many parts. Each part of the rocket falls off after pushing the satellite through the atmosphere into space. After a certain period of time all the artificial satellites will burn up like meteors.
Key Milestones in Space Technology:
Here is a look at some of the key milestones in space technology:
October 4,1957: soviet Union launches Sputnik-1.
January 4,1958: United Space launches explorer 1.
April,12,1961: Yuri Gagarin becomes the first human to enter space and
July 18,1969: launch of Apollo 11. Its puts first space station, the Skylab.
May 14, 1973: United States launches its first space station, the Skylab.
June 18,1983: Sally ride becomes first American women in space.
Feburary 19, 1986: Mir space station launches.
September 30, 2003: First privately owned spaceship launches.
August 4, 2007: Phoenix lander lands on Mars.
Kinds of Artificial Satellites:
Scientist have sent many satellites which move around the Earth. These satellites help scientists to learn about weather and many more things on the Earth.
On October 4, 1957 , Russia sent the world’s first artificial satellites, sputnik-1 into space. The name comes from a Russian word for “travelling companion of the world.” It weighed just 83 kg. It carried a thermometer and two radio transmitters which sent information about the atmosphere to the Earth. Its two transmitter only functioned for 21 days. After 57 days in orbit,it was destroyed.
Explorer 1 was the first satellite b launched by the united states of American. It was sent into space on January 31,1958. It weighed only 14kg. Explorer 1 sent information about the radiation environment in the Earth orbit.
Geostationary satellites move at a height of about 36,000 km above the Earth. At this height they move around the Earth at the same speed as the Earth moves around its axis. This satellite seems to be stationary. They are used as communication satellites. Pakistan has launched its first geostationary satellite, PAKISTAN-1R on August 11, 2011.
The land lites is a series os satellite missions. Since 1972, land set satellites have collected information about Earth from space. Landsat satellite have taken photographs of Earth’s continents and surrounding coastal regions.
Communication satellites have a great effect on our daily lives. They link remote areas on the Earth with telephone and television. Newspapers are typed and transmitted to putting machines via satellite in some countries.
Polar satellite was launched on February 24, 1996 by America. Polar satellite studies atmosphere of the Earth in polar orbit after every 18 hours. Polar satellite will help scientists to protect future satellites from atmospheric dangers.
Global Positioning System:
Satellites have improved our knowledge about space and even about out Earth. Using satellites, you can find your position anywhere in the world accurate to 10m or less. Locating the position of objects with the help of a satellite is called the global positioning system or GPS. It is freely accessible by anyone with a GPS receive.
Visiting The Space:
- In 1969, two Americans were the first men to step on the Moon. They were Neil Armstrong and Edwin Aldrin.
- India sent her first satellite Aryabhatta into space in 1975.
- Pakistan sent her satellite Badr-1 in 1990s.