2. What is Space Communication? The communication process utilizing the physical space around the Earth is known as Space Communication
3. Let us Now Understand How Space Communication Works... Let us take an example of two children playing with a ball in a closed room . The child who throws the ball acts as a transmitter and the child receiving the ball acts as a receiver . Now, the ball is the message or information that has to be transmitted .
4. Ways of Throwing The BALL... The boy can throw the ball in THREE ways:- 1 2 3 By rolling it along the ground. By throwing it directly to the receiving person. By throwing first towards the roof from where it is then reflected towards the receiving person.
5. Propagation of Electromagnetic Waves As we have seen the above example describing two children playing with a ball in a closed room, we are now in a position to describe the ways the electromagnetic waves are propagated in the space…
6. Modes of propagation 1. Ground Wave Propagation. 2. Space wave propagation or tropospheric wave propagation. 3. Sky-wave propagation or ionosphere propagation.
7. Ground Wave Propagation The field component of a wave launched from an antenna close to the surface of the earth soon becomes vertically polarized as it glides over the surface of the earth. The electrical fields due to the wave induce charges in the earth’s surface, As the wave travels, the induced charges in the earth or ground also travel along with it. This constitutes a current in the earth’s surface. Reference Diagram on the Next Slide
8. Direction of travel EARTH 2 Vertically polarized wave traveling over the surface of the earth. The solid lines represent the electric field (E) of the electromagnetic wave.
9. Space wave propagation or Tropospheric Wave Propagation The transmitted waves, traveling in a straight line, directly reach the receiver end and are then picked up by the receiving antenna. The effective reception of the broadcast of such waves is the region of the line of sight in the conventional sense. Hence, this mode of communication is sometimes termed as line of sight communication. Reference Diagram on the Next Slide
11. Sky-Wave Propagation or Ionospheric Propagation A transmitted wave going up in the sky is reflected back from the ionized region of the earth’s atmosphere, the ionosphere . The UV and other high energy radiations coming from Sun are absorbed by air molecules which get ionized and form an ionized layer of electrons and ions around the earth. The ionosphere extends from a height of ~ 80 to 300 km above the earth’s surface. Reference Diagram on the Next Slide
13. Bibliography Immense help has been taken in the form of text from the NCERT book for class XII prescribed by the CBSE. Thanks to my uncle Mr. Mohit Sachdeva who provided me with the clipart CD “Click Art Premium Collection”. Extensive images have been collected from the website:- www.digitalblasphemy.com and www.nationalgeographic.com Most of all I would like to thank my parents and my teacher Ms. Yashu Kumar for their unrelenting motivation and impetus which gave the proper path to this marvelous project.
