2.  CONTENTS :  What’s mean by satellite ?  History of Satellites :  Layer Of Atmosphere :  Generalized communication system :  What are the components of a satellite?  How Satellites Work ?  How do satellite stay in orbit ?  Why satellite are launched 36,000 Km from centre of earth ?  Types of bands :  Types of orbits :  Global position system :  Advantages And Disadvantages Of satellite :  Uses of satellite :  References :

3.  what’s mean by sATELLITE ?  Passive Satellites  Active satellites I.Natural satellites II.artificial satellites. A passive satellite only reflects received signals back to earth. Ex.moon is a natural satellite of earth Active satellites are complicated structures having a processing equipment called Transponder. An active satellite acts as a REPEATER OR  A Satellite is a solid object which revolves around some body due to the effect of gravitational forces OR  a satellite is an object which has been placed into orbit by human endeavour.

4.  History of Satellites : - ARYABHATTA (19 April 1975) First satellite that was used for communication purpose in INDIA was - ARYABHATTA (19 April 1975) - SYNCOM 3(19 Aug 1963). The first geostationary communication satellite - SYNCOM 3(19 Aug 1963). Father of geostationary communication satellite is -HAROLD ROSEN -HAROLD ROSEN (Aircraft engineer) (Aircraft engineer)  The world's first artificial satellite is the Sputnik 1 was launched in 1957

5.  Layer Of Atmosphere :  TROPOSPHERE :  STRATOSPHERE :  MESOSPHERE :  THERMOSPHERE :  EXOSPHERE :

6. INFORMA TION SOURCE Uses of informa tion TRANN SMITT ER Receiv er Channel 1 23 4 1 = Message signal. 2 = tranmitted signal. 3 = received signal. 4 = message signal.  Generalized communication system : NOISE OCCUR

7.  What are the components of a satellite? Many satellites are powered by rechargeable batteries. Small thrusters provide attitude i.e. stabilize the satellite's position in space.

8.  How Satellites Work : I.A Earth Station sends message in GHz range (Uplink). II.Satellite Receive and retransmit signals back. (Downlink) III.Difference between Downlink and Uplink frequency is 2 GHz.

9.  Why geostationary satellite are launched 36,000 km from the center of the earth?  Why geostationary satellite are launched 36,000 km from the center of the earth? 1.Gravitational force= attraction between any two objects, given by 2.Centrifugal force=an outward-directed force that normally balances the inward- directed centripital force  There are two relevant forces involved in this problem

10. Equate that 2 eqn= i.e. The tangential velocity of the satellite (v s ) is related to its orbital period, T so, Eqating that 2 eqn= As we know Then T=? and sqaring We know: G = 6.67 x 10 -11 Nm 2 kg -2 m e = 5.97 x 10 24 kg  e = 7.29 x 10 -5 rad s -1 Hence, substituting the above constants into gives: R = 35,786 km for center of earth Near about 36,000 km.

11.  How do satellites stay in orbit?  Satellites stay in orbit due to the balance of two factors: i.Velocity and ii.Gravitational pull between the Earth and the satellite. Satellites never fall into the Earth this because Earth is round and curves.

12.  Satellite Frequency Bands : inverse relationship  There is a inverse relationship between frequency and wavelength. Different kinds of satellites use different frequency bands. L–Band: 1 to 2 GHz, S-Band: 2 to 4 GHz C-Band: 4 to 8 GHz X-Band: 8 to 13 GHz Ku-Band: 13 to 18 GHz K-Band: 18 to 28 GHz Ka-Band: 28 to 40 GHz  As wavelength increases (and frequency decreases), larger antennas (satellite dishes) are necessary to gather the signal.

13.  C-band : C-band is the most common frequency spectrums used by today’s satellite. C-band satellite transmissions occupy the 4 to 8 GHz frequency range. C-band antenna is approximately 2-3 meters in diameter

14.  Ku-band : Ku-band satellite transmissions occupy the 13 to 18 GHz frequency range. Ku-band antennas can be as small as 18 inches in diameter These very high frequency transmissions mean very small wavelengths and very small diameter receiving antennas.

15.  TYPES OF ORBITS  Low-Earth-Orbit (LEOs)  Medium-Earth-Orbit (MEOs)  Geostationary (GEOs)

16.  Low-Earth-Orbit (LEO)  Altitude (600-1000 KM)  satellite gives it a better signal strength  Advantages:  Reduces transmission delay  Disadvantages:  Smaller coverage area.  Shorter life span (5-8 yrs.)

17.  Little LEOs Applications  0.8 GHz range  Small, low-cost  Used for short communications.

18.  Middle-Earth-Orbiting (MEO)  MEOs orbits between the altitudes of 8,000 - 20,000 km above the earth.  MEO satellites have a larger coverage.  These orbits are primarily reserved for communications satellites that cover the North and South Pole.  MEOs are placed in an elliptical (oval-shaped) orbit.

19. Geosynchronous-Earth-Orbit (GEO)  From the ground level the satellite appears fixed.  GEO satellites have a 24 hour view of a particular area.  Coverage to 40% of area Of planet by this satellite

20.  The Global Positioning System :  EQUATORIAL ORBIT :  POLAR CIRCULAR ORBIT :  INCLINED ORBIT :  EACH SATELLITE COVER 40% AREA  SATELLITE MAKES AN ANGLE OF 120 WITH EACH OTHER.

21.  ADVANTAGES AND DISADVANTAGES OF SATELLITE:  ADVANTAGES :  DISADVANTAGES : Make repeated observations over a given area. At a time satellites observe a larger coverage Minimum Satellite lifetime is about 10-15 years. Poor spatial resolution in the polar regions. – Launching satellites into orbit is costly.

22.  Uses of satellite: IT IS USED FOR LONG DISTANCE COMMUNICATION. IT IS SPEEDY AND RELIABLE. IT IS USED FOR WEATHER FORECASTING. (study of atmosphere,rain,sunshine at any place at perticular time) IT IS USED FOR TRANSMIT T.V. SIGNAL OVER LARGE DISTANCE COMMUNICATION. POLAR SATELLITE IS USED FOR REMOTE SENSING.

23.  REFERENCES : http://en.wikipedia.org/wiki/Geosynchronou s_satellie Geostationary Satellite(Author- Louis E.Frenzel) (Edition- Third) (Publication- Tata McGraw-Hill) http://web.mit.edu/invent/iow/rosen.html

24. -- >>BY SWAPNIL G. THAWARE