This presentation covers:
Basics of Satellite communication
Indian Communication satellites
Satellite link and elements of satellite communication
Frequency bands of satellite communication
Different orbits of satellite communication
Link budget calculations
2. 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.
3. 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.
4. 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
5. 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.
6. 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.
7. GSAT -8
Communication satellite
Configured to carry
24 high power transponders in Ku-band and
two-channel GPS Aided Geo Augmented Navigation (GAGAN) payload
8. 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.
9. 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
10. 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
11. 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.
12. 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
13. 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.
14. 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)
15. 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.
16. 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
18. Student Satellites
Universities 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
21. 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.
22. 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.
23. 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.
24. 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
25. Frequency Bands
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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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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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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.
28. 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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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.
30. 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.
31. 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.
32. 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.
33. 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
34. “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.
35. 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.
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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
38. 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.
41. 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.
42. 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.
43. 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
44. 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
45. 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.
46. Low Earth Orbit (LEO)
•IRIDIUM with 66 satellites
•GLOBALSTAR with 48
satellites
47. 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.
48. 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.
49. 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
50. 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
52. 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.
53. 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.
54. 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.
55.
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Communication Satellite
i) Communication Subsystem – consisting of
a) Transmit/ Receive Antenna.
b) Communication Transponders
ii) Support Sub-system – consisting of
a) 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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A communication subsystem consists of –
Antennas : Transmit and receive over wide
range of microwave frequencies.
Transponders : A set of transmitters and receivers
that amplify and retransmit the
incoming signal.
Communication Subsystem
A Transponder consists of a band pass filter, a down
converter and an output amplifier.
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Satellites operating in C- band carry 12 transponders.
36 MHz is widely used as transponder bandwidth, 54 and 72
MHz adopted for some satellites.(36 MHz can carry 9000
voice channels)
24 transponders can be accommodated in 500 MHz BW
through frequency reuse by orthogonal polarizations.
Transponders
6 more Transponders ( Tx no. 13 to 18 ) are present in
additional 300 MHz band in the extended C-band in INSAT
systems.
The narrower bandwidth is preferred for the transponder to
avoid inter-modulation distortion likely to occur when high
power amplifier ( TWT) is driven close to saturation.
60. 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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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
63. 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).
64. 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).
65. 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)
66. 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).
74. 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.
75. 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.
77. 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
78. 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.
79. 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
80. 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).
82. 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.
83. 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.