SATELLITE

COMMUNICATIONby Naveen Jakhar, ITS

Indian Space Research Organization

Design and development of satellites for earth observation, communication,

navigation, meteorology and space science ; design of launch vehicles .

Indian National Satellite (INSAT) programme for meeting telecommunication,

television broadcasting and developmental applications.

Indian Remote Sensing Satellite (IRS) programme for management of natural

resources and monitoring of environment using space based imagery.

Space based Applications for Societal development and Disaster Management

Support.

Communication Satellites

Indian National Satellite (INSAT) -largest domestic communication satellite systems

in Asia-Pacific region .

Established in 1983 with commissioning of INSAT-1B.

Currently operational communication satellites are INSAT-3A, INSAT-3C, INSAT-3E,

INSAT-4A, INSAT-4B, INSAT-4CR, GSAT-8, GSAT-10 and GSAT-12.

Total of 195 transponders in the C, Ext C and Ku-bands provide service to

telecommunications, television broadcasting, satellite news gathering, societal

applications, weather forecasting, disaster warning and Search & Rescue

operations.

Communication Satellites

Launch Date Launch Mass Power Launch Vehicle

GSAT-16 Dec 07, 2014 3181.6 kg (GSO) 6000 Watts Ariane-5 VA-221

GSAT-14 Jan 05, 2014 1982 kg 2600 W GSLV-D5

GSAT-7 Aug 30, 2013 2650 kg 3,000 W Ariane-5 VA-215

INSAT-3D Jul 26, 2013 2060 Kg 1164 W Ariane-5 VA-214

GSAT-10 Sep 29, 2012 3400 kg 6474 Watts Ariane-5 VA-209

GSAT-12 Jul 15, 2011 1410 kg 1430 Watts PSLV-C17

GSAT-8 May 21, 2011 3093 kg 6242 Watt Ariane-5 VA-202

GSAT-5P Dec 25, 2010 2310 kg GSLV-F06

GSAT-4 Apr 15, 2010 2220 Kg GSLV-D3

INSAT-4CR Sep 02, 2007 2,130 kg 3000 W GSLV-F04

INSAT-4B Mar 12, 2007 3025 Kg 5859 W Ariane5

INSAT-4A Dec 22, 2005 3081 Kg 5922 W ARIANE5-V169

GSAT -16

Advanced communication satellite, positioned at 55 deg East longitude in the

Geostationary orbit .

The designed on-orbit operational life of GSAT-16 is 12 years.

GSAT-16 is configured to carry a total of 48 communication transponders –

24 Nos. in C-band

12 Nos. in Ext C-band

12 Nos. in Ku-band

All transponders of 36MHz bandwidth

Footprint covers Indian mainland and Andaman & Nicobar islands

GSAT-16 carries a Ku-band beacon to help accurately point ground antennas

towards the satellite.

GSAT – 10

Communication satellite, configured to carry 30 transponders

& GPS Aided GEO Augmented Navigation (GAGAN) payload.

GAGAN payload provides Satellite-based Navigation services

with accuracy required for civil aviation applications.

Transponders -

12 Nos. in Ku-band

12 Nos. in C-band

6 nos. in Ext C-band

Each with 36 MHz usable bandwidth

Footprint covering Indian mainland and islands.

Ku-band beacon to help in accurately pointing ground

GSAT -8

Communication satellite

Configured to carry

24 high power transponders in Ku-band and

two-channel GPS Aided Geo Augmented Navigation (GAGAN) payload

Earth Observation Satellites

Starting with IRS-1A in 1988, ISRO has launched many remote sensing satellites.

Eleven operational satellites are in orbit – RESOURCESAT-1 and 2, CARTOSAT-1, 2,

2A, 2B, RISAT-1 and 2, OCEANSAT-2, Megha-Tropiques and SARAL.

Data from these satellites is used for applications covering agriculture, water

resources, urban planning, rural development, mineral prospecting, environment,

forestry, ocean resources and disaster management.

Earth Observation Satellites

Launch Date

Launch

Mass Power

Launch

Vehicle Orbit Type

SARAL Feb 25, 2013 407 kg 906 W PSLV-C20 LEO

RISAT-1 Apr 26, 2012 1858 kg 2200 W PSLV-C19 LEO

Megha-

Tropiques

Oct 12, 2011 1000 kg 1325 W PSLV-C18 LEO

RESOURCESAT-

2

Apr 20, 2011 1206 kg 1250 W PSLV-C16 LEO

CARTOSAT - 2B Jul 12, 2010 694 kg 930 W PSLV-C15 LEO

Oceansat-2 Sep 23, 2009 960 kg 1360W PSLV-C14 LEO

RISAT-2 Apr 20, 2009 300 kg PSLV-C12 LEO

IMS-1 Apr 28, 2008 83 kg 220 W PSLV-C9 LEO

CARTOSAT – 2A Apr 28, 2008 690 Kg 900 W PSLV-C9 LEO

Experimental SatellitesISRO has launched many small satellites for experimental purposes - Remote

Sensing, Atmospheric Studies, Payload Development, Orbit Controls, recovery

technology etc.

Launch Date Launch Mass Power

Launch

Vehicle Orbit Type

SRE – 1 Jan 10, 2007 550 kg

Apple Jun 19, 1981 670 kg 210 Ariane -1(V-

3)

GSO

RS-1 Jul 18, 1980 35 kg 16 Watts

RTP Aug 10, 1979 35 kg

Aryabhata Apr 19, 1975 360 kg 46 Watts

Satellite Navigation service

ISRO is establishing the Indian Regional Navigation Satellite System (IRNSS) to meet

user requirements of the positioning, navigation and timing based on independent

satellite navigation system.

Space Segment consists of seven satellites. All satellites will be visible at all times

in the Indian region.

Ground Segment provides monitoring of the constellation status, computation of

the orbital , clock parameters and navigation data uploading.

Satellite Navigation service

Launch

Date

Launch

Mass Power

Launch

Vehicle Orbit Type

Application

IRNSS 1D Mar 28,

2015

PSLV-C27 GSO Navigation

IRNSS 1C Nov 10,

2014

Navigation

IRNSS-1B Apr 04,

2014

1432 kg 1660 W PSLV-C24 Navigation

IRNSS-1A Jul 01,

2013

1425 kg 1660 W PSLV-C22 Navigation

Scientific & Exploration Research in areas like astronomy, astrophysics, planetary and earth sciences,

atmospheric sciences and theoretical physics.

A series of sounding rockets are available for atmospheric experiments.

Several scientific instruments have been flown on satellites especially to

direct celestial X-ray and gamma-ray bursts.

Mars Orbiter Mission

India's first interplanetary mission to planet Mars with an orbiter craft

designed to orbit Mars in an elliptical orbit.

Configured to carry out observation of physical features of Mars and limited

study of Martian atmosphere .

Payloads

Mars Colour Camera (MCC)

Thermal Infrared Imaging Spectrometer (TIS)

Methane Sensor for Mars (MSM)

Mars Exospheric Neutral Composition Analyser (MENCA)

Lyman Alpha Photometer (LAP)

Chandrayaan-1

India's first mission to Moon, was launched successfully on October 22,

2008 from Sriharikota.

The spacecraft was orbiting around the Moon at a height of 100 km from

the lunar surface for chemical, mineralogical and photo-geologic mapping

of the Moon.

After the successful completion of all the major mission objectives, the

orbit has been raised to 200 km during May 2009.

Small Satellites

To provide platform for stand-alone payloads for

earth imaging and science missions .

Indian Mini Satellite -1 (IMS-1)

IMS-1 bus - developed with payload capability of 30

kg.

First mission of the IMS-1 series was launched in 2008

as co-passenger along with Cartosat 2A.

Indian Mini Satellite -2 (IMS-2) Bus

IMS-2 Bus - payload capability of around 200kg. The

first mission of IMS-2 is SARAL.

Small Satellites

Launch

Date

Launch

Mass Power

Launc

h

Vehicl

e

Orbit

Type

Applicat

ion

SARAL Feb 25,

2013

407 kg 906 W PSLV-

C20

LEO Earth

Observat

ion

YOUTH

SAT

Apr 20,

2011

92 kg Solar

Array

genera

ting

230 W,

one

10.5 AH

Li-ion

PSLV-

C16

Student SatellitesUniversities and educational institutions can venture

into space technology :

Development of Payload

Development of payloads may comprise of detectors,

electronics and associated algorithms - experimental

payload on the ISRO’s on-going projects.

Satellite Design & Fabrication by

Universities/Institutions

Universities can design, fabricate, test the satellite

Bus & Payload and deliver the integrated spacecraft

to ISRO.

Student Satellites

Launch

Date

Launch

Mass Power

Launch

Vehicle

Jugnu Oct 12,

2011

3 kg

SRMSat Oct 12,

2011

10.9 kg

YOUTHSA

T

Apr 20,

2011

92 kg Solar

Array

generatin

g 230 W,

one 10.5

AH Li-ion

battery

PSLV-C16

STUDSAT Jul 12,

2010

Less than

1 kg

ANUSAT Apr 20,

2009

40 kg

SATELLITE LINK

Satellite Communication

Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.

The two stations can use a satellite as a relay station for their communication.

One Earth Station sends a transmission to the satellite. This is called a Uplink.

The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.

Satellite Comm v/s Terrestrial Comm

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 center of the coverage area.

Satellite to Satellite communication is very precise.

Higher Bandwidths are available for use.

Disadvantages of Satellites

Launching satellites into orbit is costly.

Satellite bandwidth is gradually becoming used up.

There is a larger propagation delay in satellite communication than in

terrestrial communication.

Satellite Communication - Services

Fixed Service Satellites (FSS)

• Example: Point to Point Communication

Broadcast Service Satellites (BSS)

• Example: Satellite Television/Radio called Direct Broadcast Service (DBS)/DTH.

Mobile Service Satellites (MSS)

• Example: Satellite Phones

Frequency Bands

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Overview of Satellite Communications25

Band Freq range Applications

1. VLF 10-30 KHz World wide Telegraphy

2. LF 30-300 KHz Marine & Navigation

3. MF 300-3000 KHz MW & SW Broadcasting

4. HF 3-30 MHz

5. VHF 30-300 MHz MARR, TV Radar, Aero plane,

Navigation

6. UHF 300-3000 MHz TV, UHF

7. SHF(Super High

Freq.)

3-30 GHz Microwave & Satellite

8. EHF(Extremely

High Freq.)

30-300 GHz Experimental

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Overview of Satellite Communications26

M/W Frequency Bands

L 1-2 GHz

S 2-4 GHz

C 4-8 GHz

X 8-12 GHz

Ku 12-18 GHz

K 18-27 GHz

Ka 27-40 GHz

V 40-75 GHz

W 75-110 GHz

mm 110-300 GHz

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Overview of Satellite Communications27

C- Band :

U/L : 5.925 – 6.425 GHz.

D/L : 3.7 – 4.2 G Hz. Total 500 MHz BW.

Frequency Bands For Satellite Communication

Extended C- Band :

U/L : 6.725 – 7.025 GHz.

D/L : 4.5 – 4.8 G Hz. Additional 300 MHz BW.

C-Band

C-band is mostly used for fixed services such as PSTN, Internet Trunking and

mobile feeder links.

Transmissions are immune to atmospheric conditions such as snow and rain.

Earth Station antennas are large - typically 4.5 to 18 m in diameter.

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Overview of Satellite Communications29

Frequency Bands For Satellite Communication

Ku band :

U/L : 14.0 - 14.5 G Hz.

D/L : 10.95 – 11.2 and 11.45 - 11.7 GHz.

A total of 500 MHz BW in Ku band.

Ku-Band

Generally used for fixed services such as Very Small Aperture Terminal (VSAT),

corporate networks and small businesses that use a small transceiver linked to

satellite .

Ku-band serves Internet trunking and video distribution applications.

Earth Stations are smaller as compared to C-band, with antenna diameter of 4

m or less.

Ku band

Higher frequency of Ku-band makes it more susceptible to adverse weather

conditions than C-band. Ku-band is generally offered in “Spot” beams.

Applications include VSAT, rural telephony, satellite news gathering,

Videoconferencing and multimedia services.

Ka -band

Ka-band operates in the 18-30 GHz range largely for broadband

applications.

Used for high-bandwidth interactive services such as high-speed Internet,

videoconferencing and multimedia applications.

Ka-band transmissions are even more sensitive to poor weather conditions

than Ku-band.

Beams Satellites support a variety of “beam” types to allow

the satellite to focus its power at different levels to

particular locations.

This provides a trade-off between the size of the

geographic area in which signals can be received and

the amount of power used to send or receive the

signal.

Beam types supported:

C-Band Global C-Band Zone

C-Band Hemi Ku-Band Spot

“Global” beam

Radiated power of the satellite beam is directed at the equator and spreads

outward.

Global beam provides widespread coverage but provides less power. This

means that a larger antenna must be used with a global beam.

Used by carriers who require multiple points within coverage area and have

access to a large antenna.

Other Beams

Some satellite beams direct the satellite’s power to specific areas. These are

called “Hemi,” “Zone” and “Spot” beams.

Hemi and Zone beams essentially offer approximately one half and one quarter of

the coverage of a global beam, respectively.

Spot beams – in Ku band .They provide more power and, therefore, very small, low-

cost antennas can be used. This makes it an excellent solution for corporate

network applications.

The Orbits

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Overview of Satellite Communications37

Earth Orbits for Satellites

Orbit Definition Altitude Range (km) Period (Hours) (above surface of the earth)

LEO 150 to 1,000 1.5 to 1.8

MEO 5,000 to 10,000 3.5 to 6

GEO 36,000 24

Geo-stationary Satellite: Precisely 35,768 km in the plane of the

equator

Delay approx 240msec

Geostationary Earth Orbit (GEO)

These satellites are in orbit 35,768 km above the

earth’s surface along the equator.

Satellite in Geostationary orbit revolves 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.

Geostationary Earth Orbit

EARTHEARTH

36,0

00Km

PERIOD24 HRS

EQUATOR

GEO-STATIONARYORBIT

GLOBAL COVERAGE WITH GEOSTATIONARY SATELLITESCLARKE’S CONCEPT

THE EARTH

Geostationary Earth Orbit (GEO)

Advantages

A GEO satellite’s distance from earth gives it a large coverage area.

GEO satellites have a 24 hour view of a particular area.

These factors make it ideal for satellite broadcast and other multipoint

applications.

Geostationary Earth Orbit (GEO)

Disadvantages

A GEO satellite’s distance to earth causes 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.

Geostationary Orbit (GEO)

The orbit is circular. The orbit is in equatorial plane i.e.

directly above the equator and thus inclination is zero.

There is ONLY one geostationary orbit.

The angular velocity of the satellite is equal to angular

velocity of earth.

Period of revolution is equal to period of rotation of earth.

Finish one revolution around the earth in exactly one day

i.e. 23 hours, 56 Minutes and 4.1 seconds .

If the satellite is moving in the circular-equatorial orbit

and its angular velocity is equal to earth’s angular velocity,

the satellite is said to be moving along with the earth. This

satellite would appear stationary from the earth.

Geosynchronous Orbit

The orbit is NOT circular. The orbit is NOT in equatorial

plane but it’s in inclined orbit. There are many

geosynchronous orbits.

The angular velocity of the satellite is equal to angular

velocity of earth.

Period of revolution is equal to period of rotation of earth

i.e. one revolution around the earth in exactly one day i.e.

23 hours, 56 Minutes and 4.1 seconds. Yet it does NOT

appear stationary from the earth. It looks oscillating but

NOT stationary and that is why it is called Geosynchronous.

It is practically NOT possible to achieve an absolute

geostationary orbit. So, the terms geostationary and

Low Earth Orbit (LEO)

Satellites are much closer to the earth than GEO satellites, ranging from

500 to 1,500 km above the surface.

Satellites don’t stay in fixed position relative to the earth 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.

Low Earth Orbit (LEO)

•IRIDIUM with 66 satellites

•GLOBALSTAR with 48

satellites

Low Earth Orbit (LEO)

Advantages

Satellite’s proximity to earth compared to a GEO satellite provides better

signal strength and less time delay, which makes it better for point to point

communication.

LEO satellite’s smaller area of coverage is less of a waste of bandwidth.

Low Earth Orbit (LEO)

Disadvantages

A network of LEO satellites is needed, which can be costly.

LEO satellites have to compensate for Doppler shifts caused by their relative

movement.

Atmospheric drag affects LEO satellites, causing gradual orbital deterioration.

Low lifetime 5-7 years.

Highest rate of deposition of orbital debris.

Low Earth Orbit (LEO)

Circular/slightly elliptical orbit under 2000 km

Orbit period ranges from 1.5 to 2 hours

Diameter of coverage is about 8000 km

Round-trip signal propagation delay less than 20 ms

Maximum satellite visible time up to 20 min

System must cope with large Doppler shifts

Atmospheric drag results in orbital deterioration

MEO Satellite Characteristics

Circular orbit at an altitude in the range of 5000 to 12,000 km

Orbit period of 6 hours

Diameter of coverage is 10,000 to 15,000 km

Round trip signal propagation delay less than 50 ms

Maximum satellite visible time is a few hours

Medium Earth Orbit (MEO)

•ICO with 10 satellites

Medium Earth Orbit (MEO)

Advantage : Satellite’s longer duration of visibility and wider footprint

means fewer satellites are needed in a MEO network than a LEO network.

Disadvantage : MEO satellite’s distance causes longer time delay and

weaker received signal than a LEO satellite, though not as bad as a GEO

satellite.

Other Orbits

Molniya Orbit Satellites

Used by Russia for decades.

Elliptical orbit. The satellite remains in a nearly fixed position relative to earth

for eight hours.

Three Molniya satellites can act like a GEO satellite.

Useful in near polar regions.

Other Orbits

High Altitude Platform (HAP)

New idea in satellite communication.

A blimp or plane around 20 km above the earth’s surface is used as a satellite.

HAPs would have very small coverage area, but would have a comparatively strong signal.

Cheaper to put in position, but would require a lot of them in a network.

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Overview of Satellite Communications56

Communication Satellitei) Communication Subsystem – consisting of

a) Transmit/ Receive Antenna.

b) Communication Transponders

ii) Support Sub-system – consisting ofa) Structure

b) Attitude and Orbit Control System (AOCS) - AOCS

is needed to get the satellite into the correct

orbit and keep it there.

c) Propulsion system

d) Electric Power System

e) Thermal control

f) Telemetry and Tele-command system

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Overview of Satellite Communications57

A communication subsystem consists of –

Antennas : Transmit and receive over widerange of microwave frequencies.

Transponders : A set of transmitters and receiversthat amplify and retransmit theincoming signal.

Communication Subsystem

A Transponder consists of a band pass filter, a downconverter and an output amplifier.

Support Subsystem

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Overview of Satellite Communications59

Satellites operating in C- band carry 12 transponders.

36 MHz is widely used as transponder bandwidth, 54 and 72MHz adopted for some satellites.(36 MHz can carry 9000voice channels)

24 transponders can be accommodated in 500 MHz BWthrough frequency reuse by orthogonal polarizations.

Transponders

6 more Transponders ( Tx no. 13 to 18 ) are present inadditional 300 MHz band in the extended C-band in INSATsystems.

The narrower bandwidth is preferred for the transponder toavoid inter-modulation distortion likely to occur when highpower amplifier ( TWT) is driven close to saturation.

Satellite Earth Station

Earth Stations are used to communicate with satellites.

When a satellite is within an Earth Station's line of sight, the earth

station is said to have a view of the satellite.

It is possible for a satellite to communicate with more than one

Earth Station at a time.

An Earth Station that follows a satellite not in geostationary orbit, is

called a tracking station.

Earth stations use dish-shaped antenna. Diameter varies depending

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Overview of Satellite Communications60

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Overview of Satellite Communications61

Satellite Footprint

Downlink EIRP (Effective Isotropic Radiated Power)

is 32 dbw at Beam center.

The footprint of a satellite is the ground area that

its transponders offer coverage.

Primary Coverage Area - 3 db contour EIRP 32 dbw .

Secondary Coverage Area - 6 db contour EIRP 29 dbw

Tertiary Coverage Area - 9 db contour EIRP 26 dbw

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Overview of Satellite Communications62

Satellite footprint on Asia Pacific

Region

INMARSAT

International Maritime Satellite Organisation - a satellite communications

network for the maritime community.

The name was later changed to "International Mobile Satellite

Organization" when it began to provide services to aircraft and portable

users.

Service provider - M/s Tata Communications Ltd. (TCL).

INMARSAT

TCL/VSNL was given the ILD licence to provide INMARSAT services .

TCL is providing Land Mobile services using INMARSAT-B, INMARSAT-C, INMARSAT-M,

Mini-M & M-4 terminals to certain organizations after obtaining NOC from the DoT.

These INMARSAT services are being provided by TCL through their Land Earth

Station (Gateway) at Arvi (Pune).

INMARSAT Uses

Maritime Communications including ‘Global Maritime Distress and Safety System’

(GMDSS)-

GMDSS is an internationally agreed set of safety procedures and

communication protocols used to increase safety and make it easier to rescue

distressed ships.

As land mobile for

i. Rescue Operations during any disaster (e.g. in Uttarakhand, AP, Orissa)

ii. Combat Operations (by security forces and paramilitary forces)

INMARSAT

Provides satellite services with a constellation of four satellites which are

located in the Geo-stationary earth orbit.

The constellation provide global coverage. The constellation I-3 satellites

were launched in 1996. Still being used in India.

In 2005 , launched I-4 series of satellites for BGAN (Broadband Global Area

Network).

Global Service Reach

Inmarsat 98% of the world’s landmass and all ocean

regions

GSM 10% of the world’s landmass

BGAN Services

• Basic Services – Inherently IP-based

– Regular PSTN, ISDN and IP services

– Internet access (including web browsing)

– Intranet access (including virtual private networks)

– Video Conferencing

– Internet streaming (audio/video)

– Data file transfer

– E-mail and messaging (including GPRS/UMTS 2.5/3G

SMS)

– IP Facsimile

Inmarsat-4

Orbital Positions F1 : IOR

F2 : AOR-W

Prime Contractor : Astrium

10 year lifetime (minimum)

Up to 200 spot beams

Bandwidth : 34/34 MHz

Eirp:t

Inmarsat-A

Inmarsat-B

Inmarsat-C

Inmarsat Phone (mini-M)

Direct-to-Home television (DTH)

TV Service that uses direct-broadcast satellites is known as direct broadcast

satellite television (DBSTV) or direct-to-home television (DTH).

Refers to services transmitted by satellite in specific frequency bands: 11.7-

12.2 GHz.

DTH signals can be received at homes with dish antenna of diameter 60 to

90 cm.

Direct-to-Home television (DTH)

DTH operators have introduced a large number of new interactive

applications over delivery platforms.

India has the most competitive direct-broadcast satellite market with seven

operators for more than 110 million television homes.

Number of Subscribers using DTH television is more than 60 million.

Direct to Home TV

TATA Sky INSAT 4A

Reliance Big TV Measat 3

Sun Direct Measat3

Sun Direct HD INSAT 4B

DD Direct Plus INSAT 4B

DISH TV NSS6, Asiasat 5

DISH Tru HD Asiasat 5

Airtel Digital TV SES 7

Videocon ST2

Direct to Home TV

Global positioning Service(GPS)

Satellite navigation system that provides location and time information in all

weather conditions, anywhere on or near the earth where there is an

unobstructed line of sight to four or more GPS satellites.

United States government created the system, maintains it, and makes it

freely accessible to anyone with a GPS receiver.

The system provides critical capabilities to military, civil, and commercial

users around the world.

Global positioning Service(GPS)

GPS concept is based on time.

The satellites carry very stable atomic clocks that are synchronized to each

other and to ground clocks. Any drift from true time maintained on the

ground is corrected daily. Likewise, the satellite locations are monitored

precisely.

Number of satellites – 32

Orbit - MEO

Global positioning Service(GPS)

GPS satellites continuously transmit their current time and position.

GPS receiver monitors multiple satellites and solves equations to determine

the exact position of the receiver and its deviation from true time.

At a minimum, four satellites must be in view of the receiver for it to

compute four unknown quantities (three position coordinates and clock

deviation from satellite time).

Global Positioning System (GPS)

Global positioning Service(GPS)

Indian Regional Navigation Satellite System (IRNSS) is an

autonomous satellite navigation system developed by ISRO which would be

under complete control of Indian Govt.

The requirement has arisen because access to foreign controlled global

navigation system (GPS) is not guaranteed in hostile situations.

Global positioning Service(GPS)

IRNSS will provide two services –

Standard Positioning Service for civilian use,

Restricted Service for military users.

Missile targeting could be an important military application.

IRNSS would have seven satellites, all are already placed in orbit.

The constellation of seven satellites is expected to operate from 2016

onwards.

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