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بسم اهلل الرمحن الرحيم

SATELLITE APPLICATIONS SUB: SATELLITE COMUNICATIONS

5TH YEAR 9TH SEMESTER

UNIVERSITY OF BAHRI

COLLEGE OF ENGINEERING & ARCHITECTURE

ELECTRICAL ENGINEERING(COMM.)

SUBMITTED BY: NADER BABO DUKHUN

SUPERVISOR: DR. ZOHAIR MOHAMMED

DATE: 13TH OF DEC- 2016

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Contents:

Introduction

Satellite Applications

Communications Satellites

Earth Observation Satellites

Reconnaissance Satellites

Astronomical Satellites

Weather Satellites

Navigation Satellites

Summary

References

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Introduction

A satellite is an artificial object which has been intentionally placed into

orbit. Such objects are sometimes called artificial satellites to distinguish them

from natural satellites such as Earth's Moon.

The world's first artificial satellite, the Sputnik 1, was launched by the Soviet

Union in 1957. Since then, thousands of satellites have been launched into

orbit around the Earth. A few large satellites have been launched in parts and

assembled in orbit. Artificial satellites from more than 40 countries have been

launched by ten nations. About a thousand satellites are currently operational,

and thousands of unused satellites and other space debris are in orbit. Over a

dozen space probes have been placed into orbit around other bodies and

become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn,

a few asteroids, and the Sun.

Satellites are used for a large number of purposes. Common types include

military and civilian Earth observation satellites, communications satellites,

navigation satellites, weather satellites, and research satellites. Space stations

and human spacecraft in orbit are also satellites. Satellite orbits vary greatly,

depending on the purpose of the satellite, and are classified in a number of

ways. Well-known (overlapping) classes include low Earth orbit, polar orbit,

and geostationary orbit.

About 6,600 satellites have been launched. The latest estimates are that 3,600

remain in orbit. Of those, about 1,000 are operational; the rest have lived out

their useful lives and are part of the space debris. Approximately 500

operational satellites are in Low-Earth orbit, 50 are in Medium-Earth orbit (at

20,000 km), and the rest are in geostationary orbit (at 36,000 km).

Satellites are usually semi-independent computer-controlled systems. Satellite

subsystems attend many tasks, such as power generation, thermal control,

telemetry, attitude control and orbit control.

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Satellite Applications

There are many applications for satellites in today's world. Ever since the first

satellite, Sputnik 1, was launched in 1957, large numbers of satellites have

been launched into space to meet a variety of needs. As satellite technology,

has developed over the years, so as the number of applications to which they

can be put. Whatever the type of satellite it is necessary to be able to

communicate with them, and in view of the large distances, the only feasible

technology is radio. As such radio communication is an integral part of any

satellite system, whatever its application as discussed below

Communications Satellites –

Broadband Digital Communications

Broadband satellites transmit high-speed data and video directly to consumers

and businesses. Markets for broadband services also include interactive TV,

wholesale telecommunications, telephony, and point-of-sale communications,

such as credit card transactions and inventory control.

Direct-Broadcast Services

Direct-broadcast satellites (DBS) transmit signals for direct reception by the

general public, such as satellite television and radio. Satellite signals are sent

directly to users through their own receiving antennas or satellite dishes, in

contrast to satellite/cable systems in which signals are received by a ground

station, and re-broadcast to users by cable.

Environmental Monitoring

Environmental monitoring satellites carry highly sensitive imagers and

sounders to monitor the Earth's environment, including the vertical thermal

structure of the atmosphere; the movement and formation of clouds; ocean

temperatures; snow levels; glacial movement; and volcanic activity. Large-scale

computers use this data to model the entire earth's atmosphere and create

weather forecasts such as those provided by national weather services in the

U.S. and abroad.

These satellites are typically self-contained systems that carry their own

communications systems for distributing the data they gather in the form

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reports and other products for analyzing the condition of the environment.

Satellites are particularly useful in this case because they can provide

continuous coverage of very large geographic regions.

Fixed-Satellite Services

Satellites providing Fixed-Satellite Services (FSS) transmit radio

communications between ground Earth stations at fixed locations. Satellite-

transmitted information is carried in the form of radio-frequency signals. Any

number of satellites may be used to link these stations. Earth stations that are

part of fixed-satellite services networks also use satellite news gathering

vehicles to broadcast from media events, such as sporting events or news

conferences. In addition, FSS satellites provide a wide variety of services

including paging networks and point-of-sale support, such as credit card

transactions and inventory control.

Government

Providing X-band satellite communications services to governments is a new

commercial application with substantial growth potential. SSL has designed

and built two X-band satellites, which will be available for lease to government

users in the United States and Spain, as well as other friendly and allied nations

within the satellites' extensive coverage areas. Government communications

use specially allocated frequency bands and waveforms.

Beyond environmental applications, government sensors gather intelligence in

various forms, including radar, infrared imaging, and optical sensing.

Mobile Satellite Services

Mobile Satellite Services (MSS) use a constellation of satellites that provide

communications services to mobile and portable wireless devices, such as

cellular phones and global positioning systems. The satellite constellation is

interconnected with land-based cellular networks or ancillary terrestrial

components that allow for interactive mobile-to-mobile and mobile-to-fixed

voice, data, and multimedia communications worldwide. With repeaters

located on orbit, the interference of traditional fixed-ground terminals can be

eliminated.

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Earth Observation Satellites –

these satellites are used for observing the earth's surface and as a result they

are often termed geographical satellites. Understand and analyzing global

environmental conditions is an essential element of guaranteeing our safety

and quality of life. Among other things, we need to be able to spot

environmental disasters in a timely manner, and to monitor and manage the

Earth’s natural resources. For this purpose, a number of Earth Observation

satellites are in orbit for Earth observations. Data collected by these satellites

allow us to understand the processes and interactions among land masses,

oceans, and atmosphere. The utility of different data sets for different

applications are agriculture, forestry, geology, risk management, cartography,

environment, and defense.

Agriculture

Agriculture is one of the most important application fields using Earth

Observation data from all missions, where other data sources are often too

expensive, or too restricted in scope.Typical applications include crop

inventory, yield prediction, soil/crop condition monitoring and subsidy control.

The scale of products varies, but typical applications are based on the

recognition of individual agricultural parcels.

Forestry

EO data has assumed great importance in forest mapping and management,

fire damage monitoring and the increasingly important problem of illegal

logging in many countries. Typical applications include inventory & updating,

Mapping, Change detection, Forest Health Analyses, Fragmentation Analyses,

Forest road maps, Digital Elevation Model.

Geology

Geology and related oil, mineral and gas exploration activities make up an

application segment that takes full advantage of satellite capabilities. The

large-scale satellite view allows the generation of Rock Unit Maps and Tectonic

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Structure Maps. Interferometry allows the generation of Digital Elevation

Models (DEMs) and the monitoring of mining subsidence, while radar data are

a powerful tool for off-shore oil seep detection and monitoring. Alternative

methodologies, such as the use of existing published maps, ground survey

mapping or aerial photography, when available, need be used only when very

local and detailed information is required.

Risk management

Risk management is one of the fields where EO data may play a primary role.

Three different risk situations may be considered:

Pre-crisis-During crisis- Post-crisis

Products needed in the first situation are mainly related to the collection of

land cover, geological and hydrological information, while near-real time

mapping and tracking of events is required in crisis and post crisis situations.

Currently satellite data are commonly used for the management of risk

situations, but very demanding user requirements (particularly for better revisit

times), prevent fully operational use. There are unexploited opportunities in

this field.

In the three possible risk management situations, crisis prevention is currently

seen as the main opportunity, much more than crisis monitoring and damage

assessment. This is mainly due to the fact that the coverage needs of crisis

monitoring and damage assessment are less than those required for

prevention or for monitoring of an on-going crisis. In addition, the number of

crises occurring around the world in one year remains rather small. The

importance of post-crisis analysis could be improved if the insurance sector

should start operational use of satellite data for the assessment of damage

due to natural disasters.

Cartography

Earth Observation data make an excellent basis for medium to large scale

cartography. Consequently, this segment makes extensive use of satellite data,

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especially in those situations where the requirements for accuracy can be met,

and alternative data sources are too expensive or even unavailable. Satellite

data, with different processing levels, are used for the generation of

cartography and digital elevation models.

Environment

Earth Observation data offer powerful solutions for environmental monitoring.

The data can be used mainly - Land Use / Land Cover maps, Hydrological /

Watershed map, Wildlife Habitat Maps, Land Unit Maps Soil Contamination

Map, Surface Water Condition Maps, Wetland Analyses, Quarries and Waste

Identification, Desertification analysis.

Defense & Security

For the defense and security, EO information is a key information source, and it

is handled with more and more sophisticated Geological Information System

instruments. The main applications are the generation of maps, target

monitoring and detection, and digital elevation model generation.

Reconnaissance Satellites

these satellites, are able to see objects on the ground and are accordingly

used for military purposes. As such their performance and operation is kept

secret and not publicized.

Astronomical Satellites:

these satellites are used for the observation of distant stars and other objects

in space. Placing an observation point in space removes the unwanted effects

of the atmosphere and enables far greater levels of detail to be seen than

would be possible on earth where many observatories are placed on mountain

tops that experience low levels of cloud. The most famous astronomical

satellite is the Hubble Telescope. Although now reaching the end of its life it

has enabled scientists to see many things that would otherwise not have been

possible. Nevertheless, it did suffer some major design setbacks that were only

discovered once it was in orbit.

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Weather Satellites:

as the name implies these satellites are used to monitor the weather. They

have helped considerably in the forecasting of the weather and have helped

provide a much better understanding not only of the underlying phenomena,

but also in enabling predictions to be made. A variety of these satellites are in

use and include the NOAA series.

Weather forecast use a variety of observations from which to analyses the

current state of the atmosphere. Since the launch of the first weather satellite

in 1960 global observations have been possible, even in the remotest areas.

Observation as obtained from satellite used in Numerical Weather Prediction

(NWP) model.

During the 1970s and 1980s a wide range of satellite missions have been

launched from which many different meteorological observations could be

estimated. Some satellite instruments allowed improved estimation of

moisture, cloud and rainfall. Others allowed estimation of wind velocity by

tracking features (e.g. clouds) visible in the imagery or surface wind vectors

from microwave backscatter.

Satellite imagery (visible, infrared and microwave)

The most basic form of satellite imagery provides pictures of the current cloud

conditions. This is a familiar sight on TV weather forecasts. However, satellite

imagery can also undergo various types of quantitative processing to obtain

information on important meteorological variables such as wind speed and

direction, cloud height, surface temperature, sea ice cover, vegetation cover,

precipitation, etc.

The first meteorological satellite was launched in 1960 by the USA and

provided cloud cover photography. Originally, satellite images were treated

purely as qualitative pictures, which were manually viewed and interpreted by

meteorologists. Nowadays though, satellite imagery undergoes a great deal of

mathematical manipulation and can yield quantitative analyses of atmospheric

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temperature, humidity, motion and many more meteorological variables. The

major advantage of satellites is their ability to produce near-global coverage,

which becomes especially important over oceans and remote, unpopulated

land regions, where other methods of observation are impracticable. Over

large areas of the southern hemisphere, satellites are the only means of Earth

observation. As well as observing changes in surface features such as

vegetation and sea surface temperature, satellite imagery can also capture the

development of transient features such as clouds of water or ice and plumes of

ash or dust.

Two types of satellite having on board instruments used for earth

weather images:

Polar orbiters are positioned about 900 km above the surface of the Earth, in a

sun synchronous orbit, which means they see the same part of the Earth at the

same time each day. Polar orbiters make about 14 orbits a day and can view all

parts of the atmosphere at least twice a day. Although their temporal

resolution is limited, they have high spatial resolution (typically around 1 km

between pixels) since they are relatively close to the Earth's surface.

Geostationary satellites are positioned about 36,000 km above the equator in a

geostationary orbit, which means they are always fixed in position above one

part of the Earth. These satellites scan continuously (hence have high temporal

resolution 15-30 minutes), but have limited spatial resolution (typically 3-10

km between pixels).

Radiance is measured by the satellite instrumentation and stored as digital

values in two-dimensional arrays of pixels, which make up the image. Different

instruments scan at different wavelength bands, and provide different

information about the atmosphere:

Infrared radiation, particularly around 12.5 µm, tells us about the temperature

of emitting bodies, such as clouds or the surface in cloud-free regions. IR

images are particularly good for viewing clouds and images can be produced

at night.

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Water vapour radiation, centered around 6.7 µm, measures radiation in the

water-vapour absorption band. WV images are good for viewing water vapour

distributions in cloud-free areas, and for viewing clouds. Most of the radiation

sensed is from the 300-600 hPa layer.

Visible radiation, produced in a wavelength band ~ 0.5-0.9 µm, shows clouds

but only by reflected sunlight, so no images are produced at night

Navigation Satellites:

Navigation satellite is an artificial satellite stationed in space for the purposes

of navigation. Satellite navigation is a space-based radio positioning system

that includes one or more satellite constellations, augmented as necessary to

support the intended operation, and that provides 24-hour three-dimensional

position, velocity and time information to suitably equipped users anywhere

on, or near, the surface of Earth. A satellite navigation system provides users

with sufficient accuracy and integrity of information to be useable for critical

navigation applications. The GPS system is the first core element of the

satellite navigation system widely available to civilian users. The Russian

satellite navigation system, GLONASS, which is similar in operation, is another

satellite constellation element of GNSS.

The current constellation consists of 21 operational satellites and 3 active

spares. Satellites are in orbits with approximately 12-hour periods operating at

an altitude of 20,200 kilometres. The orbital constellation consists of six orbital

planes, each inclined with respect to the equatorial plane by about 55 degrees.

Such an arrangement ensures that at any time there are at least four (and up

to 12) satellites above the horizon available for simultaneous measurements.

GPS satellites transmit on two L-band frequencies: 1.57542 GHz (L1) and

1.22760 GHz (L2). The L1 signal has a sequence encoded on the carrier

frequency by a modulation technique which contains two codes, a precision (P)

code and a coarse/acquisition (C/A) code. The L2 carrier contains only P-code

that is encrypted for military and authorized civilian users. Most commercially

available GPS receivers utilize the L1 signal and the C/A code.

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P-code users determine their geocentric positions instantly to about 5 metres

with a single hand-held satellite receiver. The C/A codes repeat every

millisecond and are available to every user. These codes are also usable for

positioning but they provide only about 20- to 30-metre accuracy.

GPS-equipped balloons are monitoring holes in the ozone layer over the Polar

Regions, and air quality is being monitored using GNSS receivers. Buoys

tracking major oil spills transmit data using GNSS. Archaeologists and

explorers are using the system.

Summary:

There are now many thousands of satellites in orbit around the Earth. Many

are in operations, while some that have not yet fallen out of orbit are still

circling the Earth. The operational satellites provide many of the services on

which we rely today. Without them many of the services and applications in

our daily life which we have come to accept as normal would not be so nearly

to achieve by other means.

References:

Wikipedia

http://www.radio-

electronics.com/info/satellite/satellite_types/satellite_applications.php

http://www.angkasa.gov.my/?q=en/node/264

http://www.suparco.gov.pk/pages/applications-satellite.asp

http://www.sslmda.com/html/products/applications.html

Satellite Technology: Principles and Applications, 2nd Edition (*Anil K. Maini, Varsha

Agrawal)