EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
UNIT – I
SATELLITE ORBITS
Kepler’s Laws, Newton’s law, orbital parameters, orbital perturbations, station keeping, geo stationary
and non Geo-stationary orbits – Look Angle Determination – Limits of visibility – eclipse – Sub satellite
point – Sun transit outage – Launching Procedures – launch vehicles and propulsion.
1.1 Kepler’s Laws, Newton’s law
1.2 Orbital Parameters
1.3 Orbital Perturbations
1.4 Station Keeping
1.5 GeoStationary And Non Geo-Stationary Orbits
1.6 Near GeoStationary orbit
1.7 Look Angle Determination
1.8 Limits of Visibility
1.9 Eclipse and Sun transit outage
1.10 Subsatellite point
1.11 Launching Procedures
1.11.1 Launching Orbits
1.11.2 Launch vehicles
1.11.3 Launching of geostationary satellite
1.12 Launch Vehicles And Propulsion
1.12.1 Principle of Rocket Population
1.12.1.1 The Rocket Equation
1.12.1.2 Thrust
1.12.2 Launch from an expandable Launcher
1.12.2.1 Launch from an expandable Launcher
1.12.3 Launch from a Reusable Launcher
1.12.4 Launching of geostationary satellite
1
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
Introduction:-
Satellite:-
In astronomical terms, a satellite is a celestial body that orbits a round a planet.
Example: The moon is a satellite of Earth.
In aerospace terms, a satellite a space vehicle launched by humans and orbits earth (or) another
celestial body.
Communications Satellite: It is a microwave repeater in the sky that consists of a diverse combination
of one or more components including transmitter, receiver, amplifier, regenerator, filter onboard
computer, multiplexer, demultiplexer, antenna, waveguide etc.
A satellite radio repeater is also called transponder. This is usually a combination of transmitter and
receiver.
Types:-
Generally satellite is classified into types.
(a) Natural satellite Moon is an example for Natural Satellite
(b) Artificial satellite Man-made satellite
Satellite
Active Satellite Passive Satellite
Active Satellite:-
Active Satellite employ ‘Regenerative technology’ which consists of demodulation, reshaping,
regenerating, processing, frequency translation, switching and amplification processes.
Block used for this purpose is called transponder.
It is also called as Microwave repeaters
Example: Commutation Satellite
Passive Satellite:-
Passive Satellite is a passive reflector which reflects signals back to earth as there are no gain
devices on based to amplify the signals.
They are just used to link two stations through space and they are not useful for communication
application.
Satellite system:-
Satellite system consists of one (or) more satellites, a ground – based station to control the operation
of the system and uses network earth stations that presides the interface facilities for the transmission and
reception of terrestrial communications traffic.
2
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
How a satellite works?
One Earth station transmits the signals to the satellite at Uplink frequency. Up link frequency is
the frequency at which Earth station is communicating with a satellite.
The satellite transponder process the signal and sends it to the second Earth station at another
frequency called downlink frequency.
Advantages:-
The advantages of satellite communication over terrestrial communication are
1. Large coverage area.
2. Higher Bandwidths are available for use.
3. Transmission cost of a satellite is independent of the distance from the center of the coverage area.
4. Satellite to satellite communication is very precise.
Disadvantages:-
1. Launching satellite into orbit is costly.
2. Satellite Bandwidth is gradually becoming used up.
3. Larger propagation delay.
Frequency Allocations for satellite services:-
According to ITU – International Telecommunication Union world is divided into three regions.
Region 1 : Europe, Africa, Soviet Union, Mongolia.
Region 2 : North and South America, Greenland
Region 3 : Asia, Australia, South West Pacific.
Services provided by satellite:-
1. Fixed satellite services (FSS) – for telephone Network and television.
2. Broadcasting satellite services (BSS) – Direct broadcast to home (DBS (or) DTH)
3. Mobile satellite services – Land Mobile, Maritime Mobile and Aeronautical Mobile.
4. Navigational satellite service – Service to Global positioning systems (GPS)
5. Meteorological satellite service – Search and receive operations.
TABLE 1. Frequency Band Designations
3
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
, EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
1.1 Kepler’s Laws, Newton’s law
1. Explain how Kepler’s and Newton’s laws are used to describe the orbit.(April 2014,Nov/Dec
2011,Nov/Dec 2010,April/May 2010,Nov/Dec 2009,May/June 2009)[Dec 2021]
2. An ophthalmology department is planning to perform CATARACT surgery for patients through
experts using a satellite link. How kepler's law of planetary motion support in launching a satellite
for such applications? Discuss the conceptual view. [May 2022][Nov 2023][Apr 2023]
Kepler’s Laws:-
In the early seven tenth century, German Astronomer Johannes kepler (1571 – 1630), discovered
the laws that govern satellite motion.
The laws of planetary motion describe the shape of the orbit, the velocities of the planet and the
distance a planet is with respect to the sun.
Kepler’s laws can be applied to any two bodies in space that interact through gravitation.
The larger of the 2 bodies is called “Primary” and the smaller is called “Secondary (or) Satellite”.
Kepler First Law:-
Kepler’s first law states that the path followed by a satellite around the primary (like earth) will be an
ellipse.
Ellipse as two focal points F1 & F2.
Figure1.1.The foci F1 and F2, the semimajor axis a, and the semiminor axis b of an ellipse.
The Centre of mass of two body system called ‘barycentre’ is always centered on one of the foci.
Since from two body, earth has enormous mass, centre is located at centre of earth itself (one of the
foci)
Where, a Semi major axis
b Semi minor axis
a2 b2
Eccentricity, e → (1.1)
a
for elliptical orbit, 0 < e < 1
if e = 0, then the orbit is a circular
Kelper’s second law:-
Kelper’s second law is known as the “Law of areas”.
4
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
UNIT – I
SATELLITE ORBITS
Kepler’s Laws, Newton’s law, orbital parameters, orbital perturbations, station keeping, geo stationary
and non Geo-stationary orbits – Look Angle Determination – Limits of visibility – eclipse – Sub satellite
point – Sun transit outage – Launching Procedures – launch vehicles and propulsion.
1.1 Kepler’s Laws, Newton’s law
1.2 Orbital Parameters
1.3 Orbital Perturbations
1.4 Station Keeping
1.5 GeoStationary And Non Geo-Stationary Orbits
1.6 Near GeoStationary orbit
1.7 Look Angle Determination
1.8 Limits of Visibility
1.9 Eclipse and Sun transit outage
1.10 Subsatellite point
1.11 Launching Procedures
1.11.1 Launching Orbits
1.11.2 Launch vehicles
1.11.3 Launching of geostationary satellite
1.12 Launch Vehicles And Propulsion
1.12.1 Principle of Rocket Population
1.12.1.1 The Rocket Equation
1.12.1.2 Thrust
1.12.2 Launch from an expandable Launcher
1.12.2.1 Launch from an expandable Launcher
1.12.3 Launch from a Reusable Launcher
1.12.4 Launching of geostationary satellite
1
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
Introduction:-
Satellite:-
In astronomical terms, a satellite is a celestial body that orbits a round a planet.
Example: The moon is a satellite of Earth.
In aerospace terms, a satellite a space vehicle launched by humans and orbits earth (or) another
celestial body.
Communications Satellite: It is a microwave repeater in the sky that consists of a diverse combination
of one or more components including transmitter, receiver, amplifier, regenerator, filter onboard
computer, multiplexer, demultiplexer, antenna, waveguide etc.
A satellite radio repeater is also called transponder. This is usually a combination of transmitter and
receiver.
Types:-
Generally satellite is classified into types.
(a) Natural satellite Moon is an example for Natural Satellite
(b) Artificial satellite Man-made satellite
Satellite
Active Satellite Passive Satellite
Active Satellite:-
Active Satellite employ ‘Regenerative technology’ which consists of demodulation, reshaping,
regenerating, processing, frequency translation, switching and amplification processes.
Block used for this purpose is called transponder.
It is also called as Microwave repeaters
Example: Commutation Satellite
Passive Satellite:-
Passive Satellite is a passive reflector which reflects signals back to earth as there are no gain
devices on based to amplify the signals.
They are just used to link two stations through space and they are not useful for communication
application.
Satellite system:-
Satellite system consists of one (or) more satellites, a ground – based station to control the operation
of the system and uses network earth stations that presides the interface facilities for the transmission and
reception of terrestrial communications traffic.
2
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
How a satellite works?
One Earth station transmits the signals to the satellite at Uplink frequency. Up link frequency is
the frequency at which Earth station is communicating with a satellite.
The satellite transponder process the signal and sends it to the second Earth station at another
frequency called downlink frequency.
Advantages:-
The advantages of satellite communication over terrestrial communication are
1. Large coverage area.
2. Higher Bandwidths are available for use.
3. Transmission cost of a satellite is independent of the distance from the center of the coverage area.
4. Satellite to satellite communication is very precise.
Disadvantages:-
1. Launching satellite into orbit is costly.
2. Satellite Bandwidth is gradually becoming used up.
3. Larger propagation delay.
Frequency Allocations for satellite services:-
According to ITU – International Telecommunication Union world is divided into three regions.
Region 1 : Europe, Africa, Soviet Union, Mongolia.
Region 2 : North and South America, Greenland
Region 3 : Asia, Australia, South West Pacific.
Services provided by satellite:-
1. Fixed satellite services (FSS) – for telephone Network and television.
2. Broadcasting satellite services (BSS) – Direct broadcast to home (DBS (or) DTH)
3. Mobile satellite services – Land Mobile, Maritime Mobile and Aeronautical Mobile.
4. Navigational satellite service – Service to Global positioning systems (GPS)
5. Meteorological satellite service – Search and receive operations.
TABLE 1. Frequency Band Designations
3
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
, EC8094 SATELLITE COMMUNICATION UNIT I - SATELLITE ORBITS
1.1 Kepler’s Laws, Newton’s law
1. Explain how Kepler’s and Newton’s laws are used to describe the orbit.(April 2014,Nov/Dec
2011,Nov/Dec 2010,April/May 2010,Nov/Dec 2009,May/June 2009)[Dec 2021]
2. An ophthalmology department is planning to perform CATARACT surgery for patients through
experts using a satellite link. How kepler's law of planetary motion support in launching a satellite
for such applications? Discuss the conceptual view. [May 2022][Nov 2023][Apr 2023]
Kepler’s Laws:-
In the early seven tenth century, German Astronomer Johannes kepler (1571 – 1630), discovered
the laws that govern satellite motion.
The laws of planetary motion describe the shape of the orbit, the velocities of the planet and the
distance a planet is with respect to the sun.
Kepler’s laws can be applied to any two bodies in space that interact through gravitation.
The larger of the 2 bodies is called “Primary” and the smaller is called “Secondary (or) Satellite”.
Kepler First Law:-
Kepler’s first law states that the path followed by a satellite around the primary (like earth) will be an
ellipse.
Ellipse as two focal points F1 & F2.
Figure1.1.The foci F1 and F2, the semimajor axis a, and the semiminor axis b of an ellipse.
The Centre of mass of two body system called ‘barycentre’ is always centered on one of the foci.
Since from two body, earth has enormous mass, centre is located at centre of earth itself (one of the
foci)
Where, a Semi major axis
b Semi minor axis
a2 b2
Eccentricity, e → (1.1)
a
for elliptical orbit, 0 < e < 1
if e = 0, then the orbit is a circular
Kelper’s second law:-
Kelper’s second law is known as the “Law of areas”.
4
Compiled by: Mr. S.Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
