physics presentation on the topic "Artifical Satellites".

2. 1. Hafiza Zunaira Liaqat
2. Namra Asif
3. Moona Kanwal
4. Rida Akbar
5. Iqra Zulfiqar

4. 
 A satellite is basically an object which revolves around another object of
a relatively larger size… they can be natural or artificial..
What we are going to discuss are Artificial Satellites..
 NASA describes An artificial satellite as a manufactured object that
continuously orbits Earth or some other body in space. Most artificial
satellites orbit Earth.

5. Artificial Satellites could be said as a useful
by-product of the cold war. In 1955, the
United States and the Soviet Union announced
plans to launch artificial satellites…
• On Oct. 4, 1957, the Soviet Union
launched Sputnik 1, the first artificial
satellite. It circled Earth once every 96
minutes and transmitted radio signals that
could be received on Earth.
• On Nov. 3, 1957, the Soviets launched a
second satellite, Sputnik 2. It carried a dog
named Laika, the first animal to soar in
space.
• The United States launched its first
satellite, Explorer 1, on Jan. 3 1, 1958, and
its second, Vanguard 1, on March 17, 1958.

6. Sputnik II with Laika Explorer I

7. The 1960s saw rapid increase in the number of spacecrafts
being launched by US and Soviet Union which lead to , what is
known today , THE SPACE RACE…
In August 1960, the United States launched the first
communications satellite, Echo I. This satellite reflected radio
signals back to Earth.
In April 1960, the first weather satellite, Tiros I, sent pictures of
clouds to Earth.
The U.S. Navy developed the first navigation satellites. The Transit
I B navigation satellite first orbited in April 1960.
By 1965, more than 100 satellites were being placed in orbit each
year.

9.  STEP –I : Building a satellite
Every satellite carries special instruments
that enable it to perform its mission. For
example, a satellite that studies the
universe has a telescope. A satellite that
helps forecast the weather carries
cameras to track the movement of
clouds.
In addition to such mission-specific
instruments, all satellites have basic
subsystems, groups of devices that help
the instruments work together and keep
the satellite operating. For example, a
power subsystem generates, stores, and
distributes a satellite's electric power.
This subsystem may include panels of
solar cells that gather energy from the
sun. Command and data handling
subsystems consist of computers that
gather and process data from the
instruments and execute commands
from Earth.
A satellite's instruments and subsystems are
designed, built, and tested individually.
Workers install them on the satellite one at a
time until the satellite is complete. Then the
satellite is tested under conditions like those
that the satellite will encounter during
launch and while in space. If the satellite
passes all tests, it is ready to be launched
 STEP-II : Launching the satellite
Space shuttles carry some satellites into
space, but most satellites are launched by
rockets that fall into the ocean after their fuel
is spent. Many satellites require minor
adjustments of their orbit before they begin
to perform their function. Built-in rockets
called thrusters make these adjustments.
Once a satellite is placed into a stable orbit, it
can remain there for a long time without
further adjustment.

10.  STEP III: Performing the mission
Most satellites operate are directed from
a control centre on Earth. Computers
and human operators at the control
centre monitor the satellite's position,
send instructions to its computers, and
retrieve information that the satellite has
gathered. The control centre
communicates with the satellite by radio.
Ground stations within the satellite's
range send and receive the radio signals.
A satellite does not usually receive
constant direction from its control
centre. It is like an orbiting robot. It
controls its solar panels to keep them
pointed toward the sun and keeps its
antennas ready to receive commands. Its
instruments automatically collect
information.
Satellites in a high altitude, geosynchronous
orbit are always in contact with Earth.
Ground stations can contact satellites in
low orbits as often as 12 times a day. During
each contact, the satellite transmits
information and receives instructions. Each
contact must be completed during the time
the satellite passes overhead -- about 10
minutes.
If some part of a satellite breaks down, but
the satellite remains capable of doing useful
work, the satellite owner usually will
continue to operate it. In some cases,
ground controllers can repair or reprogram
the satellite. In rare instances, space shuttle
crews have retrieved and repaired satellites
in space. If the satellite can no longer
perform usefully and cannot be repaired or
reprogrammed, operators from the control
centre will send a signal to shut it off.

11.  STEP IV: Falling from orbit
A satellite remains in orbit until
its velocity decreases and
gravitational force pulls it down
into a relatively dense part of the
atmosphere. A satellite slows
down due to occasional impact
with air molecules in the upper
atmosphere and the gentle
pressure of the sun's energy.
When the gravitational force
pulls the satellite down far
enough into the atmosphere, the
satellite rapidly compresses the
air in front of it. This air
becomes so hot that most or all
of the satellite burns up.
Fig.: A satellite burning up while falling
from the space

12. I. Scientific Research Satellites...
Scientific research satellites gather data for
scientific analysis. These satellites are
usually designed to perform one of three
kinds of missions. (1) Some gather
information about the composition and
effects of the space near Earth. They may
be placed in any of various orbits,
depending on the type of measurements
they are to make. (2) Other satellites
record changes in Earth and its
atmosphere. Many of them travel in sun-
synchronous, polar orbits. (3) Still others
observe planets, stars, and other distant
objects. Most of these satellites operate in
low altitude orbits. Scientific research
satellites also orbit other planets, the
moon, and the sun.

13. II. Weather Satellites…
 Weather satellites help scientists study
weather patterns and forecast the
weather. Weather satellites observe the
atmospheric conditions over large areas.
 Some weather satellites travel in a sun-
synchronous, polar orbit, from which
they make close, detailed observations of
weather over the entire Earth. Their
instruments measure cloud cover,
temperature, air pressure, precipitation,
and the chemical composition of the
atmosphere. Because these satellites
always observe Earth at the same local
time of day, scientists can easily compare
weather data collected under constant
sunlight conditions. The network of
weather satellites in these orbits also
function as a search and rescue system.
They are equipped to detect distress
signals from all commercial, and many
private, planes and ships.

14. III. Communications Satellites..
Communications satellites serve as relay
stations, receiving radio signals from one
location and transmitting them to
another. A communications satellite can
relay several television programs or many
thousands of telephone calls at once.
Communications satellites are usually
put in a high altitude, geosynchronous
orbit over a ground station. A ground
station has a large dish antenna for
transmitting and receiving radio signals.
Sometimes, a group of low orbit
communications satellites arranged in a
network, called a constellation, work
together by relaying information to each
other and to users on the ground.
Countries and commercial organizations,
such as television broadcasters and
telephone companies, use these satellites
continuously.
 A communications satellite, such as the
Tracking and Data Relay Satellite (TDRS)
shown here, relays radio, television, and
other signals between different points in
space and on Earth.

15. IV. Navigation Satellite….
 Navigation satellites enable operators of
aircraft, ships, and land vehicles
anywhere on Earth to determine their
locations with great accuracy. Hikers and
other people on foot can also use the
satellites for this purpose. The satellites
send out radio signals that are picked up
by a computerized receiver carried on a
vehicle or held in the hand.
 Navigation satellites operate in networks,
and signals from a network can reach
receivers anywhere on Earth. The
receiver calculates its distance from at
least three satellites whose signals it has
received. It uses this information to
determine its location.

16. V. Military Satellites…
Military satellites include
weather, communications,
navigation, and Earth observing
satellites used for military
purposes. Some military satellites
-- often called "spy satellites" --
can detect the launch of missiles,
the course of ships at sea, and the
movement of military equipment
on the ground.
And some of them even carry
weapons like missiles and have the
capability to attack deep within
enemy territory..
 A MILSTAR satellite in orbit..

17. VI. Earth Observing Satellites…
Earth observing satellites are used to map
and monitor our planet's resources and
ever-changing chemical life cycles. They
follow sun-synchronous, polar orbits.
Under constant, consistent illumination
from the sun, they take pictures in
different colours of visible light and non-
visible radiation. Computers on Earth
combine and analyze the pictures.
Scientists use Earth observing satellites
to locate mineral deposits, to determine
the location and size of freshwater
supplies, to identify sources of pollution
and study its effects, and to detect the
spread of disease in crops and forests.

18.  Aryabhata was India's first satellite, named after the great
Indian astronomer of the same name. It was launched by
the Soviet Union on 19 April 1975 from Kapustin Yar
using a Cosmos-3M launch vehicle.
 Aryabhata was built by the Indian Space Research
Organization (ISRO) to conduct experiments related to
astronomy. The 96.3 minute orbit had an apogee of 619
km and a perigee of 563 km, at an inclination of 50.7
degrees. Aryabhata was built to conduct experiments in X-
ray astronomy, aeronomics, and solar physics.
 The spacecraft was a 26-sided polygon 1.4 m in diameter.
All faces (except the top and bottom) were covered with
solar cells.
 A power failure halted experiments after 4 days in orbit.
All signals from the spacecraft were lost after 5 days of
operation. The satellite re-entered the Earth's atmosphere
on 11 February 1992.
 Several other satellites have been launched since then
namely the INSATs, IRS, the Chandrayana Mission etc..
 Launch Vehicles built by the ISRO such as PSLV, GSLV
have proved to be hugely successful in the commercial
field.

19. APOLLO 11
 The APOLLO 11 mission was the
first manned mission to land on the
Moon. It was the fifth human
Spaceflight of Project Apollo and
the third human voyage to the
Moon or Moon orbit .
 Launched on July 16, 1969, it carried
Mission Commander Neil Alden
Armstrong, Command Module
Pilot Michael Collins, and Lunar
Module Pilot Edwin Eugene 'Buzz'
Aldrin, Jr. On July 20, Armstrong
and Aldrin became the first humans
to land on the Moon, while Collins
orbited above.

20.  The Hubble Space
Telescope (HST) is a space
telescope that was carried into orbit
by the space shuttle in April 1990. It
is named after the
American astronomer Edwin
Hubble.
 Although not the first space
telescope, the Hubble is one of the
largest and most versatile, and is
well-known as both a vital research
tool and a public relations boon
for astronomy.
 The HST is a collaboration
between NASA and the European
Space Agency
 HST is the only space telescope that
works in the visible and the
ultraviolet range of light..

21.  The International Space Station (ISS) is an
internationally developed research facility currently being
assembled in Low Earth Orbit. On-orbit construction of the
station began in 1998 and is scheduled to be complete by
2011, with operations continuing until at least 2015. The ISS
orbits at an altitude of approximately 350 kilometres
(220 mi) above the surface of the Earth, travelling at an
average speed of 27,724 kilometres (17,227 mi) per hour,
completing 15.7 orbits per day. The station can be seen from
the Earth with the naked eye, and, as of 2009, is the largest
artificial satellite in Earth orbit, with a mass larger than that
of any previous space station.
 The ISS is a joint project among the space agencies of the
United States (National Aeronautics and Space
Administration—NASA), Russia (Russian Federal Space
Agency—RKA), Japan (Japan Aerospace Exploration
Agency—JAXA), Canada (Canadian Space Agency—CSA)
and ten European nations (European Space Agency—
ESA). The Brazilian Space Agency (AEB) participates
through a separate contract with NASA. The Italian Space
Agency (ASI) similarly has separate contracts for various
activities not done within the framework of ESA's ISS
projects (where Italy also fully participates). China has
reportedly expressed interest in the project, especially if it
would be able to work with the RKA, although as of 2009 it
is not involved due to objections from the United States.

23. i. Flight computer and I/O Processor: Command and data ...This is the part of the satellite that controls all
of the satellite's functions, like the satellite's brain. The flight computer directs the satellite's activity and the I/O
processor sends control data to and from the flight computer.
ii. Star Trackers and Reaction Wheels: Pointing control... Pointing control steers the satellite and consists of
sensors to avoid collisions. The preciseness of the pointing control depends on the function of the satellite -- some
satellites need to be in an exact altitude, while others can be but in a general area.
iii. High-gain Antennas, Transmitter/Receiver, and Omni Antennas: Communications...The part of
the satellite that communicates with Earth. Humans on the ground also use the communications system to convey
instructions to the flight computer. In addition, pictures and other data collected by the satellite are sent back to
Earth using the communications system.
iv. Solar Arrays and Battery: Power supply..Solar arrays make electricity from solar power, batteries store the
electricity, and distribution units send the power to where it is needed.
v. Digital Camera and Image Sensor: Mission payload... The payload includes everything the satellite may
need for its mission, i.e. a communications satellite would have antenna reflectors to send telephone and TV
signals in its payload.
vi. Thermal Blanket: Thermal control... Thermal control protects the satellite's delicate electronics from the
extreme temperature changes from sun to shade: 180 degrees above zero to 120 degrees below zero respectively.

24.  Artificial Satellites offer a wide range of possibilities for the future. With our changing
weather and natural disasters like Hurricane Katrina and the Tsunami, and a bad
hurricane season expected almost every year Artificial Satellites can help us to prepare
for these hurricanes and other natural disasters far in advance to better protect our
communities.
 Weather satellites can predict such weather, and early notice can be what we need to save
areas that will be targeted by these disasters.
 In addition, solar power satellites would provide an inexhaustible energy source without
our having to worry about using all of our natural resources, such as oil.
 We can’t think about Communication without these satellites..
 Researches in which the specimen needs to be isolated can be done aboard artificial
satellites..as well as those pertaining to astronomy.
 Remote Sensing is one of the areas where satellites have been extensively used.
 Military Forces use satellites to keep an eye on movements of enemies.
 In conclusion, Artificial Satellites can help to predict natural disasters to help us better
protect targeted areas and to use a clean energy source.
The value of Artificial Satellites will go way up as they help us face the challenges that
will arise in the future.

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• Kruczynski, Leonard R. "Artificial Satellite - MSN Encarta" MSN ENCARTA. 2006.
http://encarta.msn.com/encyclopedia_761551926_5/Artificial_Satellite.html
• Oberright, John E. "Artificial Satellite" World Book Online Reference Centre. 2004.
http://www.nasa.gov/worldbook/artificial_satellites_worldbook.html
• Pasachoff, Jay M. Astronomy. Boston: Pearson Prentice Hall, 2005.
• "Race into Space." New York Times. http://proquest.umi.com/
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