UNIT 1 SATELITE COMMUNICATION

2. BASICS: HOW SATELLITES ARE USED
• Service Types
 Fixed Service Satellites (FSS)
• Example: Point to Point Communication
 Broadcast Service Satellites (BSS)
• Example: Satellite Television/Radio
• Also called Direct Broadcast Service (DBS).
 Mobile Service Satellites (MSS)
• Example: Satellite Phones

13. IMPORTANT QUESTIONS
UNIT I –SATELLITE ORBITS
• 1.Look angle Determination
• 2.Geostationary and Non Geo Stationary Satellite Orbits
• 3.Orbital Parameters and Perturbations
• 4.Sun Transit Outage, Sub Satellite Point
• 5.Keplers Laws and newtons law
• 6.Satellite launch Vehicles and Launching Procedure.

14. UNIT II-SPACE SEGMENT
• 1.TTC
• 2.Transponders
• 3.Antenna Sub System
• 4.Attitude and Orbit control
• 5.Thermal Control and PropulsionUnit

15. UNIT III-SATELLITE LINK DESIGN
• 1.Downlink Design and Link Power Budget
• 2.Uplink Design
• 3.System noise temperature Analysis
• 4. EIRP and transmission losses5
• .Design for Specified C/NUnit

16. UNIT IV-SATELLITE ACESS AND CODING
METHODS
• 1.TDMA
• .FDMA
• 3.CDMA
• 4.SS-TDMA
• 5.Modulation and MultiplexingUnit
• Comparision of multiple access

17. UNIT V-SATELLITE APPLICATIONS
• 1.VSAT Architecture
• 2.VSAT Access Techniques
• 3.GSM Architecture
• 4.GPS
• 5.DBS
• 6.GEO and MEO

18. SATELLITE ORBITS
• Orbits=Path
• Types of orbits
• polar orbit-revolves arround the earth north poles to south poles
• equatorial orbit-equal
• inclined orbit

19. CLASSIFICATION BASED ON
ALTITUDE(HEIGHT)
• LEO-circular orbit travels at a speed of around 7.8km/sec
• It takes 90 mins to circle the earth
• Uses- remote sensing miltary purpose (100-1600 KM)
• MEO-satellite velocity 7.3km/sec(5000-10000KM)
• Used in telecommunication
• Polar orbit-it passes north to south in 20 to 30 degree
• Used in mapping
• GEO-36000KM,GTO-TRANSFER ORBIT
• HEO-Highly elliptical orbit

20. GEO SYNCHRONOUS AND GEO
STATIONARY ORBIT
36000 KM ALTITUDE
Noneed to change antenna posistion
Non circular
Inclined orbit
Many
Used for mobile communication
36000 KM ALTITUDE
Noneed to change antenna posistion
Cicular
Equatorial orbit
one

21. KEPLER’S 1ST LAW: LAW OF ORBITS
The orbits of the planets are ellipses with the sun at one focus

22. • It states that the path followed by a satellite around the primary will be
an ellipse
• An elipse has two foci length f1 and f2

23. KEPLER’S 2ND LAW: LAW OF EQUAL AREAS
The line joining the planet to the center of the sun sweeps out equal areas in equal
times
T6
T5
T4 T3
T2
T1
A2
A3
A4
A5
A6
A1

24. KEPLER’S 3RD LAW: LAW OF HARMONICS
The squares of the periods of two planets’
orbits are
proportional to each other as the cubes of
their semi-major axes:
T1
2/T2
2 = a1
3/a2
3
In English:
Orbits with the same semi-major axis will
have the same period

25. NEWTON’S LAWS
• Kepler’s laws only describe the planetary motion without attempting to
suggest any explanation as to why the motion takes place in that manner.
Sir .Issac Newton
• Derived three laws of motion.
• Derived the Law of Universal
Gravitation.
• Explained why Kepler’s laws worked.

26. NEWTON’S 1ST LAW: LAW OF INERTIA
• Every body continues in a state of uniform motion unless it is
compelled to change that state by a force imposed upon it

27. NEWTON’S 2ND LAW: LAW OF MOMENTUM
• Change in momentum is proportional to and in the direction of the force
applied
• Momentum equals mass x velocity
• Change in momentum gives: F = ma
F
F

28. NEWTON’S 3RD LAW: ACTION - REACTION
• For every action, there is an equal and opposite reaction
• Hints at conservation of momentum

29. CLASSICAL ORBITAL ELEMENTS
• Six independent quantities are sufficient to describe the size, shape and
orientation of an
orbit.
These are six Kepalarian element(refered for orbital elements)
• a, the semi-major axis
• , the eccentricity
• i, the inclination
• , the right ascension of the ascending node
• , the argument of perigee
• tp, mean anamoly

30. POSISTION OF ORBIT WITH RESPECT TO
EARTH
• SUB SATELLITE PATH-Path trace out on the earth surfaces directly
below the satellite.
• APOGUE-The point farthest from earth apogue height is shown in
‘ha’
• PERIGUE-Closest to the earth perigue height is ‘hp’.
• LINES OF APSIDES-Liine joining the perigue and apogue through
centre of earth

31. • ASCENDING NODE-The point where the orbit crosses the equatorial
plane going from S TO N
• DESCENDING NODE –N TO S
• LINES OF NODES-Line joining the ascending and descending node
through the centre of earth.
• INCLINATION-The angle b/w orbital planes and equatorial plane
• Prograde orbit –An orbit in which the satellite moves in the same
direction as the earth rotation it is also called direct orbit
• Retrograde orbit-indirect orbit its inclination is b/w 90 and 180 degree`

32. GEO STATIONARY AND NON GEO-
STATIONARY ORBITS:
• A geostationary orbit is one in which a satellite orbits the earth at
• exactly the same speed as the earth turns and at the same latitude,
specifically zero, the latitude of the equator.
• A satellite orbiting in a geostationary orbit appears to be hovering in
the same spot in the sky, and is directly over the same patch of
ground at all times.

33. • A geosynchronous orbit is one in which the satellite is synchronized
with the earth's rotation, but the orbit is tilted with respect to the plane
of the equator.
• A satellite in a geosynchronous orbit will wander up and down in
latitude, although it will stay over the same line of longitude. Although
the terms 'geostationary' and 'geosynchronous' are sometimes used
interchangeably, they are not the same technically; geostationary orbit
is a subset of all possible geosynchronous orbits.