Artificial Satellites over Natural Satellites
Types Of Satellite Orbits
Categories of Satellite
Advantages of Satellites
Disadvantages of Satellites
What is satellite networks?
A satellite network is a combination of nodes,
some of which are satellites, that provide from
one point on the earth to another. A node in
the network can be satellite, an Earth station
ARTIFICIAL SATELLITES OVER
We can install electronic equipment on the satellite to
regenerate the signal that has lost its energy during
The distance of natural satellites, such as the Moon,
from the Earth is huge, which create a long delay in
What is the period of the moon according to Kepler’s law?
The moon is located approximately 384,000 km above the earth. The radius of
the earth is 6378 km. Applying the formula, we get
Period =(1/100) (384,000 +6378)1.5 =2,439,090s=approx.(1 month)
According to Kepler’s law, what is the period of a satellite that is
located at an orbit approximately 35,786 km above the earth?
Applying the formula, we get
Period = (1/100) (35,786 +6378)1.5 =86,579 s = 24 h
Asatellite like this is said to be stationary to the earth.earth. The orbit,
as we will see, is called a geosynchronous orbit.
7/18/2014 6:37:54 PM
The area of the Earth’s surface from which an
Earth Station can transmit to or receive from a
HOW SATELLITE WORKS
Two Stations on Earth want to communicate through radio broadcast but are too far away to use
One Earth Station sends a transmission to the satellite . This is calleda Uplink.
The satellite Transponder converts the signal and sends it down tothe second earth station. This
is called a Downlink.
L 1.5 1.6 15 Low bandwidth; crowded
S 1.9 2.2 70 Low bandwidth; crowded
C 4.0 6.0 500 Terrestrial Interference
Ku 11.0 14.0 500 Rain
Ka 20.0 30.0 3500 Rain, equipment cost
L-band and S-band: is used for Mobile Satellite Services and offers good penetration
through adverse weather conditions andfoliage.
C-band: Public switched networks.
Ku-band and Ka-band: Rural telephony, satellite news gathering, high speed internet,
SATELLITE FREQUENCY BAND
video conferencing, and multimedia.
GEOSTATIONARY EARTH ORBIT (GEO)
These satellites are in orbit 35,786 km above the earth’s surface along the equator.
Objects in Geostationary orbit revolve 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.
One GEO satellite cannot cover the whole earth. It takes minimum of three satellites equidistant from each other.
AGEOsatellite’s distance from earth gives it a
large coverage area, almost a fourth of the
GEOsatellites have a 24hour view of a particular
These factors make it ideal for satellite broadcast
and other multipoint applications.
AGEOsatellite’s distance also cause it to have both a comparatively weak
signal and a time delay in the signal, which is bad for point to point
GEOsatellites, centered above the equator, have difficulty broadcasting
signals to near polar regions
MIDDLE EARTH ORBIT (MEO)
A MEO satellite is in orbit somewhere between 5,000 km and
15,000 km above the earth’s surface.
MEO satellites are visible for much longer periods of time than
LEOsatellites, usually between 2 to 8 hours.
MEO satellites have a larger coverage area than LEO
• A MEO satellite’s longer duration of visibility and wider
footprint means fewer satellites are needed in a MEO network
than a LEO network.
• Shorter time delay and stronger signal than a GEO satellite
• A MEO satellite’s distance gives it a longer time delay and
weaker signal than a LEO satellite, though not as bad as a
EXAMPLE: Global Positioning System (GPS).
GPS: EXAMPLE OF MEO
BY US DEPARTMENT
THERE ARE 24
IN SIX ORBITS.
USED FOR LAND,
SEA AND AIR
PROVIDE TIME AND
VEHICLES AND SHIPS.
THE SATELLITES IN
ARE DESIGNED IN
SUCH A WAY,
AT A TIME MINIMUM
ARE VISIBLE FROM
ANY POINT ON THE EARTH.
GPS: HOW IT WORKS ( CONT.)
Measuring the distance: The trilateration principle can find our location on
the earth if we know our distance from three satellites and know the
positionof each satellite. The position of each satellite can be calculated
by a GPSreceiver. The GPSreceiver, then, needs to find its distance from
at least three GPS satellites. Suppose all GPSsatellites and the receiver on
the earth are synchronized. Each of 24 satellites transmits a complex
signal each having a unique pattern. The receiver measures the delay
between the signals from the satellites and its copy of signals to
determine the distances to the satellites.
• LEOsatellites are much closer to the earth than GEOsatellites, ranging
from 500 to 2000 km above thesurface.
• Rotation period of 90 to 120 minutes, with speed 20,000 to 25,000
• LEOsatellites don’t stay in fixed position relative to the surface, and are
only visible for 15 to 20 minutes eachpass.
• Anetwork of LEOsatellites is necessary for LEOsatellites to be useful.
LOW EARTH ORBIT (LEO)
ALEO satellite is proximity to earth compared to a GEO satellite gives it
a better signal strength and less of a time delay, which makes it better
for point to point communication.
A LEO satellite’s smaller area of coverage is less of a waste of
• It has 66 satellites in 6 LEOorbits.
• Each have altitude of 750 km.
• Use to provide direct worldwide communication.
i.e. voice, data paging, fax, even navigation.
IRIDIUM SYSTEM: EXAMPLE OF LEO
• It has 48 satellites in 6 LEOorbits.
• Each have altitude of 1400 km.
• The ground station can create more powerful
GLOBALSTAR: EXAMPLE OF LEO
•It provides fiber-optic like (broadband channels, low error rate, and low delay)
•It has 288 satellites in 12 LEOpolar orbits.
• Each have altitude of 1350 km.
TELEDESIC: EXAMPLE OF LEO
The coverage area of a satellite greatly exceeds that of a terrestrial
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.
ADVANTAGES 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.
DISADVANTAGES OF SATELLITES