Unit 1 sc

Mar 2, 2017 satellite communication 1
S.MOUNIKA
Assistance professor
Dept of Electronics & communication Egg
Krishna Murthy institute of technology Engineering
UNIT-I COMMUNICATION SATELLITEUNIT-I COMMUNICATION SATELLITE

satellite communication 2
 Introduction
 Def of satellite ,orbit
 Types of satellites, orbits
 frequency bands ,applications
 kepler laws, satellite system
 orbital velocity, orbital period
 look angle
 effect of inclination
 solar eclipse
 Launching satellite in to GEO
 orbital perturbation

What is satellite
 A satellite is simply any body that moves
around another (usually much larger) one in
a mathematically predictable path called an
orbit
 A communication satellite is a microwave
repeater station in space that is used for
telecommunication , radio and television
signals
 The first man made satellite with radio
transmitter was in 1957
 There are about 750 satellites in the space,
most of them are used for communication

The origin of satellite
• The concept of using object in space to reflect signals for
communication was proved by Naval Research Lab in Washington
D.C. when it use the Moon to establish a very low data rate link
between Washington and Hawaii in late 1940’s.
• Russian started the Space age by successfully launching SPUTNIK the
first artificial spacecraft to orbit the earth, which transmitted
telemetry information for 21 days in Oct. 1957.
• The American followed by launching an experimental satellite
EXPLORER In 1958.
• In 1960 two satellite were deployed “Echo” & “Courier”
• In 1963 first GSO “Syncom”
• The first commercial GSO (Intelsat & Molnya) in 1965 these provides
video (Television) and voice (Telephone) for their audience

Early Satellites
Syncom
• In October 1957, the first
artificial satellite Sputnik -I was
launched.
• 1963 Clark’s idea became a
reality when the first
geosynchronous satellite SYNCOM
was successfully launched by
NASA.
•India launched its first satellite
Aryabhatta on 19 April 1975

APPLICATIONS• FIXED-TO-FIXED • Mobile to mobile
FIXED-TO-MOBILE POINT-TO-MULTIPOINT
Introduction to Satellite Communications Presented by Sally Sheridan

• Satellite communications can interconnect with any other communications
solution
• (i.e. LMR, Cellular, WiFi, etc.) via generic crossbanding equipment.
INTEROPERABILITY

VIDEO/DATA
• Fixed Satellite Service (FSS) has traditionally referred to a satellite service that
uses terrestrial terminals communicating with satellites in geosynchronous orbit.
• New technologies allow FSS to communicate with mobile platforms.
Cellular Restoration
Wi-Fi Restoral
Emergency Phone Bank
Communications On The Move
PSTN Backhaul
Voice-over-IP
Broadband Internet Access
Live Video
Telemedicine
Video Conferencing
FSS APPLICATIONS:
FSS APPLICATIONS:

BroadbandConnectivity

VIDEO/DATA
Network Restoration
TERRESTRIAL BROADBAND, LMR, CELLULAR, OR WIMAX AND WIFI
INFRASTRUCTURE RESTORATION:
VSAT networks are able to provide high-speed, two-way emergency communications
restoration in the wake of a natural or man-made disaster when all other forms of
high-speed communication are unavailable.
VSAT networks provide connectivity for restoral and contingency communications,
providing for higher volume VoIP telephony, data, video and Internet access, thereby
connecting remote locations to the rest of the world in a time of crisis.

Communications OnTheMove(COTM)
MOBILE COMMAND AND CONTROL COMMUNICATIONS:
FSS and MSS COTM solutions can provide fully mobile IP data and voice services to vehicles on the move up
to 60 mph. The comprehensive FSS COTM offering includes the terminal, teleport, and satellite capacity to
provide high performance COTM IP connectivity.
TYPICAL APPLICATIONS SUPPORTED:
Any vehicle can also serve as a mobile command post while in-route and as a ﬁxed command access point for
personnel upon arrival at the designated location when local Telco terrestrial and wireless infrastructure are not
available.
A full 10 Mbps downlink channel is delivered via FSS to the vehicle and 512
Kbps uplink channel transmitted from the vehicle to the Internet using IP support for voice, video and data
simultaneously.
Support for 802.11x wireless access allows vehicle to function as wireless hot spot access point for a First
Responder convoy while in-route or a ﬁxed hot spot for personnel upon arrival.

Elements of Satellite Communications
• The basic elements of a communication satellite
service are divided between;
• Space Segment
• Ground Segment
• The space segment consist of the spacecraft &
launch mechanism and ground segment comprises
the earth station and network control center of
entire satellite system.

Satellite Communications System
Uplink Down Link
Transmit Earth Station Receive Earth
Station
IDU IDURFT RFT
RF

Concept
Transponder
Earth station (site A) Earth station(site B)
IRRADIUM
downlinkdownlink
uplinkuplink
downlinkdownlink
uplinkuplink

Working…
• Two Stations on Earth want to communicate through radio
broadcast but are too far away to use conventional repeater.
• The two stations can use a satellite as a relay station for their
communication
• One Earth Station transmits the signals to the satellite. Up
link frequency is the frequency at which Ground Station is
communicating with Satellite
• The satellite Transponder converts the signal and sends it
down to the second earth station. This frequency is called a
Downlink frequency

The Frequency Spectrum and Typical Applications
102
104
106
108
1010
1012
1014
1016
1018
1020
Hz
Power
Systems Mittel
Welle
AM UKW
TV
Mobil
Funk
Mikro
Welle IR Lamp
Sun
Studio
X-Rays
AC Broadcast Microwave Infrared Ultraviolett X-Ray
Sat
TV
GPS
Galileo
Glonass

Radio Frequency Bands
Band Number Band Name Frequency Range Metric
Subdivision
4 VLF, Very low frequency 3-30 KHz Myriametric waves
5 LF, Low frequency 30-300 KHz Kilometric waves
6 MF, Medium frequency 300-3000 KHz Hectometric waves
7 HF, High frequency 3-30 MHz Decametric waves
8 VHF, Very high frequency 30-300 MHz
9 UHF, Ultra high frequency 300-3000 MHz Decimetric waves
10 SHF, Super high frequency 3-30 GHz Centimetric waves
11 EHF, Extra high frequency 30-300 GHz Decimillimetricwaves

Satellite Operating Frequency Bands
Frequency Range (GHz) Band Category
0.39-1.55 L MSS
1.55-5.2 S FSS & BSS
3.9-6.2 C FSS
5.2-10.9 X Military
10.9-36.0 K FSS & BSS
15.35-17.25 Ku FSS & BSS
18.3-31.0 Ka FSS

Bands:
C-Band ( )
Ku-Band ( )
Beams:
Global ( )
Hemi ( )
Zone ( )
Spot ( )
Key Input Data...

Introduction to the orbit of satelliteIntroduction to the orbit of satellite
Sir. Johannes Kepler
Derived 3 laws based upon his
observations of planetary motion.
 Planets move in elliptical orbits with the sun at one of the
foci.
 The line joining the sun and the planet sweeps out equal
areas in equal times.
 The cube of the distance of the planet from the sun is
proportional to the square of the period. r3 ά T2

Kepler’s 1st Law:: Law of Ellipses
The orbits of the planets are ellipses with the sun at one
focus

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
T1A2
A3A4
A5
A6
A1

Kepler’s 3rd Law: Law of Harmonics
 The squares of the periods of two planet’s
orbits are proportional to each other as the
cubes of their semi-major axes
T1
2/T2
2 = a1
3/a2
3
 Orbits with the same semi-major axis will
have the same period

Types of Orbits
• Geostationary orbit is when the satellite or
spacecraft is stationary in a single position
relative to the Earth
• Polar Orbit is an orbit in which your spacecraft
or your satellite crosses the orbits in a
longitudinal fashion.
• In a polar orbit, you can circle the Earth several
times during one day.
• Highly Elliptical Orbit: When the satellite
passes Earth quickly and stays away from Earth
fixed in a distant location.

Geostationary Orbit (GEO)
• Satellite has to be placed approximately 22,000 miles
(36,000 km) away from the surface of the Earth in order
to remain in a GEO orbit
• In GEO, the satellite will be on the equator and it will
remain stationary since it will have a period of 24 hours

Geosynchronous Orbit
• Geosynchronous orbit is like a geostationary orbit in the
sense that it has a period of 24 hours.
• However, unlike a GEO, it doesn’t have to be exactly above
the equator, as it can have an angle relative to Earth and the
orbit doesn’t have to be fully circular

Polar/Geostationary Orbit

Highly Elliptical Orbit
• An object in orbit about Earth moves much faster
when it is close to Earth than when it is further away.
• If the orbit is very elliptical, the satellite will spend
most of its time near apogee (the furthest point in its
orbit) where it moves very slowly.

Mar 2, 2017 31 Satellite Communications
Geostationary Earth Orbit (GEO)
 These satellites are in orbit 35,863 km above the
earth’s surface along the equator.
 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.

Advantages:
 A GEO satellite’s distance from earth gives it a
large coverage area, almost a fourth of the earth’s
surface.
 GEO satellites have a 24 hour view of a
particular area.
 These factors make it ideal for satellite broadcast
and other multipoint applications.

Disadvantages:
 GEO satellite’s 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.
GEO satellites, centered above the equator, have
difficulty broadcasting signals to near polar
regions.

The original vision
• 1945 Arthur C Clark envisaged
“extraterrestrial relays”
• # of Satellites: 03
• Period: 23 h 56 min 4.091 s
• Height: 36 000 km above
equator
• Speed of flight: 3.074 km/s

Characteristics of a Geostationary Satellite Orbit
• Eccentricity (e) 0
• Inclination of the orbital plane (i) 0º
• Period (T) 23h 56m 4s
• Semi-major axis (a) 42164 km
• Satellite altitude(R) 35786 km
• Satellite velocity (Vs) 3075 m/s
F=GMm/r2
T=2π√ a3
/µ µ=Gme=3.986x1014
m3
/s2
e=c/a V= µ(2/r-1/a) m/s

The GEOThe GEO
ε d
pRo
Ro
ζ
Elevation , distance to the satelliteElevation , distance to the satellite
Kgrav = m Me G / r2
Kzent = m r ω2
, = m v2
/ r
Angular velocity ω = 2π / T, T Period, v velocity
Kgrav = Kzent und
m Me g / r2
= m r ω2
bzw. Me g / r2
= r ω2
r 3
= Me g T2
/ ( 2π )2
The period T of the circular orbit (r in km, m = 398 601.8 km3
/s2
) is
──── ──────
T = 2 π √ r 3
/ m = 9.952 10-3
√ r 3
/ km in Seconds
p = 6.611

ε d
pRo
Ro
ζ
∆lon = LongitudeE/S - LongitudeSatellite
∆lat = LatitudeE/S - LatitudeSatellite
Space angle α: cos( α ) = cos ( ∆lon ) * cos( ∆lat )
───────────────────────────────────────
Distance d: d = Ro √ 6.6112
– 2 * 6.611 * cos α + 1
Elevation ε: sin( ε ) = [ 6.6112
Ro
2
– Ro
2
– d2
) / ( 2 Ro d ) ]
Test: α = 81.3° d = 41680 km and ε = 0°
α = 0° d = 35787 km and ε = 90°
The GEOThe GEO

Comparison Chart
Features GEO MEO LEO
Height
(km’s)
36,000 6,000-
12,000
200-3000
Time per
Orbit (hrs)
24 5-12 1.5
Speed
(kms/ hr)
11,000 19,000 27,000
Time
delay
(ms)
250 80 10
Time in
site of
Gateway
Always 2-4 hrs < 15 min
Satellites
for Global
Coverage
3 10-12 50-70

Orbital Velocity & Period
Calculations
• The trajectory followed by the satellite in
equilibrium between two opposing forces
(gravitational force and inertial centrifugal
force)
• Maximum extension at apogee and minimum
at perigee

Cont…..

Cont….

INCLINATION

Azimuth & Elevation Angle Calcuation

Cont……..

Coverage area /slant range

ECLIPSE

Cont…..

ORBITAL PERTURBATION

Unit 1 sc

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