2. CONTENTS
• INTRODUCTION
• WORKING
• ORBITS
• FREQUENCY ALLOCATION FOR SATELLITE
SYSTEMS
• SATELLITE LAUNCH VEHICLES
• ADVANTAGES OF SATELLITE
COMMUNICATION
• DISADVANTAGES OF SATELLITE
COMMUNICATION
• APPLICATIONS
• CONCLUSION
3. INTRODUCTION
The word satellite originated from the Latin word “Satellit”-
meaning an attendant, one who is constantly hovering around &
attending to a “master”
A satellite is simply any body that moves around another (usually
much larger) one in a mathematically predictable path called an
orbit
4.
5. WORKING
• The basic elements of a satellite communications system are shown in next
slide. The process begins at an earth station an installation designed to
transmit and receive signals from a satellite in orbit around the
• earth.
• Earth stations send information in the form of high powered, high
frequency (GHz range) signals to satellites which receive and retransmit the
signals back to earth where they are received by other earth stations in the
coverage area of the satellite.
•
6. CONT.........
•The area which receives a signal of useful strength from
the satellite is known as the satellite's footprint.
•The transmission system from the earth station to the
satellite is called the uplink, and the system from the
satellite to the earth station is called the downlink.
7.
8. ORBITS
GEO: ~ 36000 km from
the earth
MEO: 6000 - 20000 km
LEO: 500 - 1500 km
HEO: Highly Elliptical Orbit
Elliptical orbits are
difficulties from radiation belts.
9. GEOSTATIONARY EARTH
ORBIT (GEO)
• Objects in Geostationary orbit revolve around the earth at the same speed as the
earth rotates
• This means GEO satellites remain in the same position relative to the surface of
earth
• Because of the long distance from earth it gives a large coverage area, almost a
fourth of the earth’s surface but, this distance also cause it to have both a
comparatively weak signal and a time delay in the signal, which is bad for point to
point communication.
High transmit power needed and launching of satellites to orbit are complex and
expensive.
Not useful for global coverage for small mobile phones and data transmission, typically
used for radio and TV transmission
10. MEDIUM EARTH ORBIT (MEO)
• MEO satellites have a larger coverage area than LEO satellites
• A MEO satellite’s longer duration of visibility and wider footprint
means fewer satellites are needed in a MEO network than a LEO
network
• A MEO sMEO satellites have a larger coverage area than LEO
satellites
• A MEO satellite’s longer duration of visibility and wider footprint
means fewer satellites are needed in a MEO network than a LEO
network
• A MEO satellite’s distance gives it a longer time delay and weaker
signal than a LEO satellite, though not as bad as a GEO satellite
• atellite’s distance gives it a longer time delay and weaker signal
than a LEO satellite, though not as bad as a GEO satellite
11. LOW EARTH ORBIT (LEO)
•LEO satellites are much closer to the earth than GEO satellites,
ranging from 500 to 1,500 km above the surface
•LEO satellites don’t stay in fixed position relative to the
surface, and are only visible for 15 to 20 minutes each pass
•A network of LEO satellites is necessary for LEO satellites to
be useful to handover necessary from one satellite to another
need for routing.
12.
13. FREQUENCY ALLOCATIONS
•Frequency bands for satellite services are shared
•with terrestrial services
•Satellite signal strength is constrained to avoid interface
by it to others
•Thus a large antenna and sensitive receiver are
•needed at the earth station
14. CONT............
•Many satellites have to share a limited frequency
•band,thus co-ordination in frequency and orbital
•Location is important
•Frequency allocation all done by international
•agreements
15. FREQUENCY BANDS
• 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 12.5 GHz
• Ku-Band:12.5 to 26.5 GHz
• K-Band:18 to 26.5 GHz
• Ka-Band:26.5 to 40 GHz
16. SATELLITE LAUNCH VEHICLES
• In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a
payload from Earth's surface into outer space.
• A launch system includes the launch vehicle, the launch pad, and other
infrastructure.
• Although a carrier rocket's payload is often an artificial satellite placed
into orbit, some spaceflights, such as sounding rockets, are suborbital, while
others enable spacecraft to escape Earth orbit entirely.
• One of the example for satellite launch vehicle is PSLV(Polar Satellite
• Launch Vehicle)
17. PSLV
• The PSLV is one of world's most reliable launch vehicles.
• It has been in service for over twenty years and has launched various
satellites
• Historic missions like Chandrayaan-1, Mars Orbiter Mission, Space
Capsule Recovery Experiment, Indian Regional Navigation Satellite
System (IRNSS) etc.
• PSLV remains a favourite among various organisations as a launch service
provider and has launched over 40 satellites for 19 countries.
• In 2008 it created a record for most number of satellites placed in orbit in
one launch by launching 10 satellites into various Low Earth Orbits.
18. VEHICLE SPECIFICATIONS
Height : 44 m
•Diameter : 2.8 m
•Number of Stages : 4
•Lift Off Mass : 320 tonnes (XL)
•Variants : 3 (PSLV-G, PSLV - CA, PSLV - XL)
•First Flight : September 20, 1993
19. CONT.........
• Payload to SSPO: 1,750 kg
• PSLV earned its title 'the Workhorse of ISRO' through consistently delivering various satellites to Low Earth Orbits,
particularly the IRS series of satellites.
• It can take up to 1,750 kg of payload to Sun-Synchronous Polar Orbits of 600 km altitude.
• Payload to Sub GTO: 1,425 kg
• Due to its unmatched reliability, PSLV has also been used to launch various satellites into Geosynchronous and
Geostationary orbits, like satellites from the IRNSS constellation.
• Fourth Stage: PS4
• The PS4 is the uppermost stage of PSLV, comprising of two Earth storable liquid engines.
• Engine : 2 x PS-4
• Fuel : MMH + MON
• Max. Thrust : 7.6 x 2 kN
20. CONT......
• Third Stage: PS3
• The third stage of PSLV is a solid rocket motor that provides the upper stages high thrust after the atmospheric phase of the launch.
• Fuel : HTPB
• Max. Thrust : 240 kN
• Second Stage: PS2
• PSLV uses an Earth storable liquid rocket engine for its second stage, know as the Vikas engine, developed by Liquid Propulsion Systems Centre.
• Engine : Vikas
• Fuel : UDMH + N O
• Max. Thrust : 799 kN
• First Stage: PS1
• PSLV uses the S139 solid rocket motor that is augmented by 6 solid strap-on boosters.
• Engine : S139
• Fuel : HTPB
• Max. Thrust : 4800 kN
21. ADVANTAGES
•The coverage area of a satellite greatly exceeds
•that of a terrestrial system
•Transmission cost of a satellite is independent of
•the distance from the centre of the coverage area
•Satellite to satellite communication is very precise
•Higher bandwidths are available for use
22. DISADVANTAGES
•Launching satellites into orbits is costly
•Satellite bandwidth is gradually becoming used up
There is larger propagation delay in satellite comm-
unication than in terrestrial communication
23.
24. APPLICATIONS
• Telephony
- Fixed points, earth station, Satellite, earth station, fixed points.
• Television & Radio
- e.g. Direct broadcast satellite (DBS) & Fixed service satellite (FFS)
• Mobile satellite technology
- Special antenna called mobile satellite antenna.
• Amateur radio
- Access to OSCAR satellite.
- Low earth orbits.
• Internet
- High Speed.
- Useful for far away places.
• Military
- Uses geostationary satellites.
29. CONCLUSIONS........
•Satellite systems are not aimed to replace terrestrial system but
at complementing them
•GEO’s are ideal for TV and Radio broadcasting and they do
not need handover because of its larger footprint.
•Lifetime of GEO’s are rather high, about 15 years
•LEO’s need a network of satellites and are appropriate for
voice communications
•In LEO’s handover is frequent and routing is must
•MEO’s are in between LEO’s and GEO’s in every aspect
