SATELLITE TYPES,USES

1. Nowrin Jahan Siam,City University
A satellite is a moon, planet or machine that orbits a planet or star. For example,
Earth is a satellite because it orbits the sun. Likewise, the moon is a satellite
because it orbits Earth. Usually, the word "satellite" refers to a machine that is
launched into space and moves around Earth or another body in space.
Earth and the moon are examples of natural satellites. Thousands of artificial, or
man-made, satellites orbit Earth. Some take pictures of the planet that help
meteorologists predict weather and track hurricanes. Sometake pictures of other
planets, the sun, black holes, dark matter or faraway galaxies. These pictures help
scientists better understand the solar systemand universe.
Still other satellites are used mainly for communications, such as beaming TV
signals and phone calls around the world. A group of morethan 20 satellites make
up the Global Positioning System, or GPS. If you have a GPS receiver, these
satellites can help figure out your exact location.
Why Are Satellites Important?
The bird's-eyeview that satellites have allows them to see large areas of Earth at
one time. This ability means satellites can collect more data, more quickly, than
instruments on the ground.
Satellites also can see into spacebetter than telescopes at Earth's surface. That's
because satellites fly above the clouds, dustand molecules in the atmosphere
that can block the view fromground level.
Before satellites, TV signals didn't go very far. TV signals only travel in straight
lines. So they would quickly trail off into spaceinstead of following Earth's curve.
Sometimes mountains or tall buildings would block them. Phone calls to faraway
places werealso a problem. Setting up telephone wires over long distances or
underwater is difficult and costs a lot.
With satellites, TV signals and phone calls are sent upward to a satellite. Then,
almost instantly, the satellite can send them back down to different locations on

2. Earth.
What are satellite used for:
Satellites are manmade objects put into orbit. They often affect our
lives without our realizing it: they make us safer, provide modern
conveniences,and broadcast entertainment. Here are some of the jobs
satellites do:
Television
Satellites send television signals directly to homes, but they also are
the backbone of cable and network TV. These satellites send signals
from a central station that generates programming to smaller stations
that send the signals locally via cables or the airwaves. "At the scene"
news broadcasts, whetherlive reporting on a vote at the Capitol or
from the scene of a traffic accident, are sent from the field to the
studio via satellite,too.
Telephones
Satellites provide in-flight phone communications on airplanes, and
are often the main conduit of voice communication for rural areas and
areas where phone lines are damaged after a disaster. Satellites also
provide the primary timing source for cell phones and pagers. In 1998,
a satellite failure demonstrated this dependence; it temporarily
silenced 80 percent of the pagers in the United States, National Public
Radio was not able to distribute its broadcasts to affiliates and
broadcasted only via its website, and on the CBS Evening News, the
image of Dan Rather froze while the audio continued.
Navigation
Satellite-based navigation systems like the Navstar Global Positioning
Systems (known colloquially as GPS) enable anyone with a handheld
receiver to determine her location to within a few meters. GPS locators
are increasingly included in in-car direction services and allow car-

3. share services like Zipcar to locate their cars. GPS-based systems are
used by civilians and the military for navigation on land, sea, and air,
and are crucial in situations like a ship making a difficult course in a
harbor in bad weather or troops lost in unfamiliarterritory, where
other navigation tools may not exist.
Business & finance
Communications satellites have the ability to rapidly communicate
between a number of widely dispersed locations. This is an important
tool, allowing big manufacturingcompanies and department stores to
perform inventory management, provide instant credit card
authorization and automated teller banking services to even small
towns, pay-at-the-pump gas at freeway gas stations, and video
conferencing for international corporations.
Weather
Satellites provide meteorologists with the ability to see weather on a
global scale, allowing them to follow the effects of phenomenalike
volcanic eruptions and burning gas and oil fields, to the development
of large systems like hurricanes and El Niño.
Climate & environmental monitoring
Satellites are some of the best sources of data for climate change
research. Satellites monitorocean temperatures and prevailing
currents; data acquired by satellite-borne radars were able to show sea
levels have been rising by three mm a year over the last
decade. Imaging satellites can measure the changing sizes of glaciers,
which is difficult to do from the ground due to the remoteness and
darkness of the polar regions. Satellites can determine long-term
patterns of rainfall, vegetation cover, and emissions of greenhouse
gases.

4. Safety
Earth observation satellites can monitor ocean and wind currents as
well as the extent of forest fires, oil spills, and airborne pollution;
together this information helps organize emergency responders and
environmental cleanup. Satellites can take the "search" out of "search
and rescue" for people in distress in remote regions. Distress radio
beacons directly linked to a search and rescue satellite can lead
rescuers quickly and accurately to a land, sea, or air emergency
location.
Development
Satellites are increasingly important to the developing world. For a
country like India, with populations separated by rough terrain and
different languages, communications satellites provides remote
populations access to education and to medical expertise that would
otherwise not reach them. Earth observation satellites also allow
developing countries to practice informed resource management and
relief agencies to follow refugee population migrations.
Space science
Before the Space Age, astrophysicists were limited to studying the
universe via ground-based telescopes, and so could only use
information from the parts of the electromagneticspectrum that
penetrated the Earth's atmosphere. Many of the most interesting
phenomenaare best studied at frequencies that are best or only
accessible from space—satellite telescopes have been critical to
understanding phenomena like pulsars and black holes as well as
measuringthe age of the universe. The Hubble Space Telescope is
arguably the most valuable astronomical tool ever built!

5. Types of satellite:
Geostationary Earth Orbit (GEO)
GEO is also called geosynchronous (or synchronous) orbits, which have 23 h, 56 min.,
4.091s, or 24 hours period of revolution but are inclined with respect to the equator. Orbits
that are below a mean altitude of about 35,784 km have periods of revolution shorter than
24 hours and hence are termed as non-GEO.
GEO satellite has the ability to provide coverage of an entire hemisphere at one time.
Satellites are designed to last only about 15 years in orbit, because of the practical inability
to service a satellite in GEO and replenish consumables (Fuel, battery cells, and degraded
and failed components).
Medium Earth Orbit (MEO)
An MEO satellite is in orbit somewhere between 8,000 km and 18,000 km above the earth’s
surface. MEO satellites are similar to LEO satellites in functionality. The MEO satellites are
visible for much longer periods of time than LEO satellites, usually between 2 to 8 hours.
MEO satellites have a larger coverage area than LEO satellites.
Low Earth Orbit (LEO)
LEO satellites are much closer to the earth than GEO satellites, ranging from 500 to 1,500
km above the surface. LEO satellites don’t stay in a fixed position relative to the 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.

6. Referance: NASA satellite,ELECTRONICS CLUB,