In this Fast and ultra dynamic era, world seems handicapped without satellites. Whether it is getting the accurate weather forecasts or to dig the deep secrets of our planet and galaxies, to transfer telephone calls beyond the oceans and making the world a global village or using it as key resource in the navigation of ships and aircraft, to get the crucial news from war sites or in disaster management, to support national arm forces or to see live prime time news, live telecasts of sports everyday. There is no area untouched where we do not need satellite aid. Today, there is no other technology, which supersedes Satellite Communication.

So, What is a satellite?
A satellite is an object, which continuously orbits Earth or some other body in space. Like moon is a natural satellite of earth. Similar way human has prepared many artificial satellites most of these satellites orbit Earth. Some man-made satellites also have orbited the moon, the sun and the other planets Venus, Mars, and Jupiter. The main purpose of such satellites is to gather information about the bodies they orbit.
Space shuttle orbiters, space capsules, piloted space crafts in orbits are also comes under artificial satellite category.
The First artificial satellite was launched in 1957 by Soviet Union. The satellite was named as “SPUTNIK 1”. Today including Canada, United States of America, Russia, European countries, Japan and India, as leaders in the field, there are more than forty countries have successfully launched their satellites in space and right now there are almost 3000 satellites are in active useful operations.

The orbit of satellite can be of many types but satellites who revolves around the earth travels in four types of orbits:
  • Geo synchronous
  • Medium Altitude
  • Sun Synchronous Polar
  • Low altitude

Satellites can be broadly classified in to following types according to their purpose:
  (1) Astronomy Satellites.
  (2) Weather Satellites.
  (3) Communication Satellites
  (4) Navigation Satellites
  (5) Military Satellites
  (6) Space Exploration Satellites
  (7) Atmospheric study Satellites
  (8) Search and Rescue Satellites
  (9) Reconnaissance satellites
  (10) Remote Sensing Satellites

Astronomy Satellites: these satellites can be assumed similar as a very big telescope mounted in space which keeps floating and because of being far above to the earth orbit it does not gets affected by the earth’s heat and gases and can take 10 times more accurate pictures than a normal telescope on earth.
The example of such a satellite is Hubble space telescope.
    
Weather Satellites: gather weather data so that scientist can study weather pattern and predict weather forecast. They send as well as receive data, capture pictures of cloud patterns, these satellites have special cameras built in which gives live view of temprature od surface on the earth and near by space by following a color coding scheme the weather scientists decode the colors and get accurate information.
There are two main types of weather satellites:
 1. Geo stationary weather satellites
 2. Sun synchronous weather satellites.
Meterosat is a successfully launched weather satellite.

Navigation Satellites: These Satellites enable operators of aircraft, ships, and land vehicles anywhere on Earth to determine their locations with great accuracy.
GPS(Global Positing System) satellite is an Navigation satellite which can transfer the singals to vehicles traveling in land, water or air which helps drivers to determine their position.NAVSTAR series of satellites also are well known successful navigation satellites.

Military Satellites: These Satellites are private satellites and are developped for military use.

Communication Satellites: Communications satellites enables radio, television, and telephone transmissions to be sent live anywhere in the earth. Communication satellite receives a radio signal from a ground station on the earth, then amplifies and retransmits the signal back to a receiving station or stations on earth at a different frequency. A communication satellite travels in geosynchronous orbit, which means that it is orbiting at the same speed as the earth is revolving. The satellite stays in the same position relative to the surface of the earth, so that the broadcasting station will never lose contact with the receiver.
Canada’s Anik is an example of a communication satellite.

Atmospheric Study Satellites: these satellites are used to study the atmospheric changes on earth surface.
Polar is a recent atmospheric study satellite launched by NASA

Search and Rescue Satellites: These satellites are useful in life threatening conditions. These satellites are designed in such a way that vehicles in air and water can communicate with remote areas.

Reconnaissance Satellites: these satellites are used to spy on other countries. These satellites provided regular information of arms activities of other countries. These satellites can detect missile launching and nuclear explosion activities taking place in other counties and also can be used as orbital weapons in war situations but this use of satellites is not recommended.
Lacrosse, is the reconnaissance satellite launched by NASA.

Remote Sensing Satellites: these satellites are used to remotely observing the natural resources from the space which are useful for human being like searching the locations of Mineral resources, monitoring agricultural crops, animal migration etc.
The example of such a satellite is Radarsat by Canada.

Space Exploration Satellites:
These satellites are commonly termed as Space Probes.
These satellites travels deep towards the solar system and capture and send back the pictures and discoveries of other planets in galaxy. Like such a satellite does Exploration of Mars, such a satellites discovered Jupiter rings. Nasa’s Galileo is a Space Exploration Satellite.

Satellites are launched by space shuttles; satellite launching vehicles and rockets, which place the satellite in stable orbit. After the successful launch, the satellite remain there for a long time until their velocity decreases and gravitation force pulls it down.
Satellites technology has made people lives safe and easy.