Satellite 101

SATELLITE 101
WHAT YOU NEED TO KNOW
Colleen Jack +27826007845 colleen@patternworks.co.za

WHAT ARE SATELLITES?
• Satellites are relay stations in space for the transmission of voice, video & data communications
• They are ideally suited to meet the global communications requirements of military, government &
commercial organisations because they provide economical, scalable & highly reliable
transmission services that reach multiple sites over vast geographic areas
• Wireline & wireless lack this ability to leap across continents & oceans
• Transmissions via satellite communications systems can bypass the existing ground-based
infrastructure, linking some of the world’s most remote spots
• Satellite technology has become the solution for some of the most complicated access problems,
connecting cities across a large landmass, where copper or fibre would be cost prohibitive.
Bringing broadband to the “last mile” of residences & businesses
• The effectiveness of satellites can be diminished by weather conditions such as heavy rain
causing “Rain Fade”

WHAT IS A COMMUNICATION SATELLITE?
A communication satellite is nothing but a
microwave repeater station in space
It is helpful in telecommunications, radio & television
along with internet applications
Satellite communications involves four steps:
1. An uplink Earth station or other ground equipment
transmits the signal to the satellite
2. The satellite amplifies the incoming signal & changes
the frequency
3. The satellite transmits the signal back to Earth
4. The ground equipment receives the signal

WHAT IS THE DIFFERENCE BETWEEN
ONE-WAY & TWO-WAY SATELLITE?
In one-way satellite communication link service, the information can be
transferred from one earth station to one or more earth stations through
a satellite. That means, it provides both point to point connectivity & point
to multi point connectivity.
Examples of the one-way satellite communication link services:
• Broadcasting satellite services like Radio, TV & Internet services
• Space operations services like Telemetry, Tracking & Commanding services
• Radio determination satellite service like Position location service (GPS)

WHAT IS THE DIFFERENCE BETWEEN
ONE-WAY & TWO-WAY SATELLITE?
In two-way satellite communication link, the information can be exchanged
between any two earth stations through a satellite. It provides only point to point
connectivity. Here, the communication takes place between first earth station
(transmitter) & second earth station (receiver) on earth’s surface through a
satellite in both directions.
Examples of the two-way satellite communication link services:
• Fixed satellite services like Telephone, Fax & Data of high bit rate services
• Mobile satellite services like Land mobile, Maritime & Aero mobile communication
services

SATELLITE | Types
Fixed Satellite
Services (FSS)
Mobile Satellite
Services (MSS)
Broadcast Satellite
Services (BSS)

APPLICATIONS OF SATELLITE COMMUNICATION
• Radio broadcasting & voice communications
• TV broadcasting such as Direct To Home (DTH)
• Internet applications such as providing Internet connection for data transfer,
GPS applications, Internet surfing, etc.
• Military applications & navigations
• Remote sensing applications
• Weather condition monitoring & Forecasting

GEO = Geosynchronous Earth Orbit
MEO = Medium Earth Orbit
LEO = Low Earth Orbit
SATELLITES | Where we find them

SATELLITES | In Orbit

GEO SATELLITE | Orbital Slots

2° spacing
(1,440Km)
100Km
1st Harmonic
Beam
2nd Harmonic
Beam
Adjacent
Satellite
Adjacent
Satellite
Ground
Station
GEO SATELLITE | Location & Movement

SATELLITES | How big are they?

SATELLITE 101 | ANTENNAS
There are primarily four types of Antennas used in a Satellite:
• Wire Antennas
• Horn Antennas
• Array Antennas
• Reflector Antennas (used by broadband Satellite )

SATELLITE 101 | Reflector Antennas
• Antennas are used as receivers of
electromagnetic waves. When they hit
the shape of the parabola, the wave gets
reflected onto the feed point;
• The horn antenna acts as the receiver
antenna at its feed. When it receives this
signal, it converts it into electric signal &
forwards it to the receiver circuitry;
• In order to transmit a signal, the signal
from the feed comes out of a horn
antenna to focus the wave on to the
parabola;
• This means that the waves come out of
the focal point & strike the paraboloidal
reflector.

SATELLITE 101 | Parabolic Reflectors
• Reflector Antennas are suitable for
producing beams which have more
signal strength in one direction;
• They are highly directional antennas;
• Parabolic Reflectors increase the gain of
antennas in satellite communication
systems like telecommunications &
broadcasting.
That is why we use Parabolic
Reflectors!

EFFECTS OF THE
WEATHER
RAIN FADE
SUN OUTAGE
ADAPTIVE CODING MODULATION

THE EFFECTS OF WEATHER | Rain Fade
• Rain Fade is the physical phenomenon that deteriorates RF signals due to the presence of moisture
(rain, snow, ice) in the transmission path.
• Losses are especially prevalent at higher frequencies like AY2 Ka-band.
• Rain fade can be caused by precipitation at the uplink or downlink location.
• However, it does not need to be raining at a location for it to be affected by rain fade, as the signal
may pass through precipitation many miles away.
• Signal loss can occur due to presence of precipitation or sand on the antenna assembly.
• HN system has mechanisms built in to minimise the effect of rain fade on service known as Adaptive
Coding & Modulation (ACM) & Adaptive Inbound Selection (AIS.)

THE EFFECTS OF WEATHER | Rain Fade

SUN OUTAGE
A Sun outage, Sun transit, or Sun fade is:
• An interruption in, or distortion of geostationary satellite signals
• Caused by interference (background noise) of the sun when it falls directly
behind a satellite which an earth station is trying to receive or transmit data to
• It usually occurs briefly twice per year to satellites
The effect sweeps from north to south from approximately 20 February to 20 April,
and from south to north from approximately 20 August to 20 October, affecting any
specific location for less than 12 minutes a day for a few consecutive days.

QPSK Rate 1/2
Satellite terminals
8PSK Rate 9/10
Satellite terminals
QPSK Rate 3/4
Satellite terminals
Highest throughput
for best weather
Less aggressive modulation
for poor weather
Repeated data transmission
for bad weather
Adaptive Coding & Modulation (ACM)
On the out route, the system adjusts the tolerance
level to signal quality of a terminal based on weather
conditions (hence signal quality).
The satellite terminal measures its out route receive
quality; in situations such as rain fade or a weak
satellite footprint location, a satellite terminal can
send feedback to the NOC GTWY that then adjusts
the coding rate & modulation on the traffic to that
specific satellite terminal.
THE EFFECTS OF WEATHER | ACM

SPEED VS LATENCY VS BANDWIDTH |
What’s the difference?
• Speed measures the rate at which traffic moves within a network.
• Bandwidth is the measure of how much traffic a broadband connection
can cope with at once.
• Latency measures the round trip a network packet takes to travel from
your device to its destination.
– A low latency number means the network is running well and your
connection to another computer is fast.
– A higher latency means there is a delay somewhere in that link.

THE EFFECTS OF WEATHER
| LATENCY | PING SPEED
• 10-20 milliseconds for superfast broadband;
• 40 milliseconds for ADSL broadband;
• 60 milliseconds for mobile broadband;
• 650 milliseconds Average round trip for satellite broadband;
On a voice call you will only pick up a delay at 800 milliseconds.

Satellite 101

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