2. Satellites Overview
History
Launching of Satellites
How Satellites Work
Orbit Distance
Types: Low-Earth-Orbit (LEOs)
Medium-Earth-Orbit (MEOs)
Global Positioning System (GPS)
Geostationary (GEOs)
Applications
3.
History of Satellites
The First Satellites
The theory of satellites was simple enough - shoot something out into space
at the right speed and on the correct trajectory and it will stay up there,
orbiting Earth, for years - if not forever.
If the orbit is the right distance in space the satellite will keep pace with the
rotation of the Earth.
Early in October 1957 communications stations started picking up a regular
beeping noise coming from space.
The signals were coming from Russia's Sputnik 1, the world's first man-
made satellite.
It was January 1958, before a Jupiter rocket successfully launched Explorer
1, the first American satellite.
4. History of Satellites
On October 4, 1957, the Soviet Union successfully launched Sputnik I.
The world's first artificial satellite was about the size of a basketball,
weighed only 183 pounds, and took about 98 minutes to orbit the
Earth on its elliptical path
on November 3, Sputnik II was launched
On January 31, 1958, the United States successfully launched Explorer I
The first satellite that was used for communication purpose in INDIA was
ARYABHATTA and it was launched in 19th April.1975. APPLE was
launched in space which was the first Indian Experimental
communication satellite
INSAT (Indian National Satellite System) is a series of multipurpose
geostationary satellites launched by ISRO to satisfy the
telecommunications, broadcasting, and search-and-rescue needs of
India. Commissioned in 1983, INSAT is the largest domestic
communication system in the Asia-Pacific Region
Chandrayaan-1)). It was launched by the Indian Space Research
Organisation in October 2008, and operated until August 2009.
5. 1957
First Artificial Satellite
(Sputnik)
The first artificial satellite was
Sputnik 1, launched by the
Soviet Union on October 4,
1957. At about the size of a
basketball, Sputnik 1 was
equipped with a radio
transmitter that gave off a
beeping signal—helping the
Soviets to track it on its 98-
minute orbit and to signal to
the world that the U.S.S.R.
was the leader in space
6. Photograph courtesy
NOAA/NESDIS Headquarters
1960
First Orbiting Observations
(TIROS-1 Weather Satellite)
The first aerial images of the
Earth from space were taken by
TIROS 1 (Television InfraRed
Observation Satellite). TIROS 1
was launched in 1960 to find out if
it was possible to watch cloud
cover and weather patterns from
space. Although it was an
experimental satellite, TIROS
images were immediately put to
use by meteorologists
7. 1972
First Surveying Satellite (Landsat)
The first Landsat satellite was called
the Earth Resources Technology
Satellite, or ERTS. Since its launch on
July 23, 1972, six Landsats have
followed, with the latest, Landsat 7,
lifting off on April 15, 1999. Over the
years successive Landsats have not
only carried better land-viewing
sensors, but they have created a
valuable archive of images that are
being used to see how the land is
changing over the years. Landsat 7
carries the Enhanced Thematic
Mapper Plus, which scans the Earth in
eight bands of visible and invisible light
8. 1974
First Geostationary Satellite
(GOES)
Best known as weather satellites,
the first GOES (Geostationary
Operational Environmental Satellite)
was launched on October 16, 1975.
Their high orbits and visible-light and
infrared sensors allow for constant
surveillance of weather patterns over
the entire planet and have enabled
GOES to revolutionize the science of
weather prediction. GOES-10,
launched in 1998, images the 48
contiguous U.S. states every five
minutes.
10. To enable a satellite to orbit around any planet, we have
to consider height from which the satellite must be
thrown.
Consider yourself, if you throw a stone, it comes to earth
after some time, why? It is because of the gravitational
attraction of earth and the stone. By the Newton 's law of
gravitation, stone and earth would be attracted towards
each other by force
F = GMm / R2
Where M is mass of earth
m is mass of stone
R is distance between centre of earth and stone
11.
Since, throwing the satellite from earth's surface will make the satellite to
come down to earth's surface due to gravitational pull
F α 1/ R2
i.e. greater is the distance, lesser the force of attraction. As we have seen
earlier that value of g decreases with increase in height and expression is
given by
gh / g = g ( 1 - 2h / R )
We can say that to put on object into earth's orbit.
• Move the object to suitable height.
• Then, project it with high velocity.
Remember, less the height to which object is moved, greater the velocity
needed for projecting.
I would like to state that the velocity that I was talking about is called as ‘
ORBITAL VELOCITY
12. Satellite
A Satellite is a solid object which revolves around some heavenly
body due to the effect of gravitational forces which are mutual in
nature. We can categorize satellites in two types, namely Passive
Satellites and Active satellites. A passive satellite can be further
subdivided into two types, namely Natural satellites and artificial
satellites. A moon is a natural satellite of earth. But spherical balloon
with metal coated plastic serve as artificial satellites.
Active satellites are complicated structures having a processing
equipment called Transponder which is very vital for functioning of
the satellite. These transponders serve dual purpose i.e. provides
amplification of the incoming signal and performs the frequency
translation of the incoming signal to avoid interference between the
two signals.
13. How Satellites Work
1. A Earth Station sends
message in GHz range.
(Uplink)
2. Satellite Receive and
retransmit signals back.
(Downlink)
3. Other Earth Stations
receive message in
useful strength area.
(Footprint)
14.
15. Microwaves are electromagnetic waves with frequency from
30MHz to 1 GHz. The ionosphere cannot reflect microwaves back
to the earth. They pass through the ionosphere A satellite used to
receive microwaves and then transmit them back to the earth.
Satellites provide links in two ways. Firstly a satellite provide point
to point communication link between one ground station and the
other. One ground station transmit signal to the other satellite and
next ground station receives them from the satellite. Secondly,
satellite receives signals from one ground station and transmits to
them to the number of ground receivers.
Most satellite use frequency bandwidth through from 5.92 to
6.4GHz from transmission of data from earth to the satellite and a
frequency bandwidth from 3.7 to 4.1GHz for transmission from
satellite to the earth.
17. Low-Earth-Orbit (LEO)
Altitude (375-1000 miles)
Revolution time: 90 min - 3 hours.
Advantages:
Reduces transmission delay
Eliminates need for bulky
receiving equipment.
Disadvantages:
Smaller coverage area.
Shorter life span (5-8 yrs.)
than GEOs (10 yrs).
18. Middle-Earth-Orbiting (MEO)
MEOs orbits between the altitudes
of 5,600 and 9,500 miles.
These orbits are primarily reserved
for communications satellites that
cover the North and South Pole.
Unlike the circular orbit of the geostationary satellites,
MEOs are placed in an elliptical (oval-shaped) orbit.
19. GPS: What is it ?
A constellation of 24 satellites
The Global Positioning System (GPS) is a
space-based global navigation satellite system
(GNSS) that provides reliable location and time
information in all weather and at all times and
GPS Satellites
anywhere on or near the Earth
The Global Positioning System (GPS) is a Name: NAVSTAR
worldwide radio-navigation system formed from a Manufacturer: Rockwell International
constellation of 24 satellites and their ground Altitude: 10,900 nautical miles
stations. Weight: 1900 lbs (in orbit)
They are constantly moving, making two Size: 17 ft with solar panels
extended
complete orbits in less than 24 hours.
Orbital Period: 12 hours
These satellites are traveling at speeds of Orbital Plane: 55 degrees to
roughly 7,000 miles an hour. equatorial plane
Planned Lifespan: 7.5 years
Current constellation: 24 Block II production
satellites
The spacing of the satellites are arranged so
that a minimum of five satellites are in view
from every point on the globe.
20. Geosynchronous-Earth-Orbit (GEO)
Orbit is sychroneous
with the earths
rotation.
From the ground the
satellite appears
fixed.
Altitude is about
23,000 miles.
Coverage to 40% of
planet per satellite.
21. Basics of GEOs
Geostationary satellites are commonly used for communications and
weather-observation.The typical service life expectancy of a geostationary
satellite is 10-15 years. Because geostationary satellites circle the earth at
the equator, they are not able to provide coverage at the Northernmost and
Southernmost latitudes.
Advantages:
Weather images can be displayed.
Television broadcasts are uninterrupted.
Used to track major developments such as hurricanes 24 hours a day.
Disadvantages:
It takes longer for the signal to get to earth and back to satellite.
Increased difficulty of telephone conversations.
GEOs are not positioned in the farthest northern and southern orbits.
22. Applications
India uses its satellites communication network – one of the largest in the world – for
applications such as land management, water resources management, natural
disaster forecasting, radio networking, weather forecasting, meteorological imaging
and computer communication
The INSAT-2 satellites also provide telephone links to remote areas; data
transmission for organizations such as the mobile satellite service communications
for private operators, railways and road transport; and broadcast satellite services,
used by India’s state-owned television agency as well as commercial television
channels
ISRO has applied its technology to "telemedicine", directly connecting patients in
rural areas to medical professionals in urban locations via satellites Since high-
quality healthcare is not universally available in some of the remote areas of India,
the patients in remote areas are diagnosed and analyzed by doctors in urban
centres in real time via video conferencing
INSAT-4CR was launched on 2 September 2007 by GSLV-F04. It is a replacement
satellite of INSAT-4C which was lost when GSLV-F02 failed and had to be destroyed
on its course
This satellite is used by Airtel Digital TV and Sun Direct DTH to broadcast their DTH
services.
India to Launch 3D Weather Forecasting Satellite in 2011
