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Keilee Lynd

on 23 July 2014

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Transcript of Satellites

What are they?
Satellites usually refer to man-made machines launched into orbit that move around the Earth or another body in space. However moons and planets are also classified as satellites (known as natural satellites) as they orbit other planets and stars. Satellites are a package of radio equipment. Artificial satellites are being used constantly, significantly effecting our daily lives without us even realizing. Satellites are important as they are quicker and more accurate than any data found from the ground.
How they work?
History of Satellites
Satellites have changed immensely, in less then 60 years, from when the first prototype was made. The range of uses of satellites has increased from military and scientific research to easy access for everyone. Meteorological satellites in 1975 had only two channels to view the Earth. Modern day satellites have five imager channels. The footprint of satellites has also increased and spotbeams have been created. Satellites now have a larger carrying capacity and the likelihood of a transmission error is now near-zero.

Future Advancements
The advancements of satellites continues to change constantly. Further satellite advancements are to include the satellite communication services to be accessible all over the world. An application has also been put forward of a global satellite network which would allow computer users to bypass telephone networks and connect directly to the internet by satellite. Scientists have also currently been developing small satellites that have rapid-response, low cost and are highly capable, also filling a smaller spot in space. In the future, satellites will likely be used for traffic monitoring, domestic uses in buying new homes, planning holidays and disaster management. There are extensive possibilities of further satellite advancements.
In the past, satellites have been used in wars as spies. During the Cold War satellites took photographs of the activities of China and the Soviet Union. The photos were used to monitor weapon development and produce maps of their camps. The other first satellites were used to study the Earth's atmosphere.
Today mechanical satellites are still used to study the atmosphere but are also used for a far greater range of objects.
Satellite Orbit
Satellites are launched into space by rockets. Satellites start to orbit Earth when its speed is balanced by the pull of Earth's gravity. If this balance did not occur, the satellite would fly off into space or fall back to Earth.

Facts about the orbit of satellites:
Satellites orbit at different heights, speeds and directions. 'Polar' and 'geostationary' are the two most common types of orbit.
Geostationary satellites travel from west to east over the equator, moving in the same direction of the Earth and at the same rate the Earth spins. Geostationary satellites look like they are standing still because it's always above the same location.
Polar- orbiting satellites circle the Earth in a north to south direction. As the Earth rotates, these satellites can scan the entire globe.
It is very rare but satellites can crash into each other. When they are put into orbit, they are placed so they will avoid other satellites but orbits can change over time. Also the more satellites in space, the higher chance of a collision.
Satellites need to travel at a certain speed in space called its 'orbital velocity'. This is usually more than 28 200 km/h.
'Geocentric orbit' is the term used for an orbit of the Earth.
'Heliocentric orbit' is a term for the orbit around the Sun.
'Areocentric orbit' is the term for the orbit of Mars.
By Keilee Lynd

There are hundreds of artificial satellites that have been put into orbit.
The moon is a natural satellite as it orbits the Earth.

There are two types of satellites- passive and active. Passive satellites reflect the signal directly back to the source or other sources, where active satellites amplify the radio signal before transmitting back to the sources. Active communication satellites (used for television, radio and telephones) also convert the radio wave into another frequency so it can be distinguished from the original uplink.

The power source in a satellite is usually a solar panel or battery. Using solar cells is the most efficient source as it can conveniently get sunlight, which is then changed into electricity.

Satellites can carry cameras or scientific sensors that collect data. They either point towards the Earth or towards space depending on which data they are collecting.

Depending on the purpose of the satellite, there are different methods of how they work, but all satellites have an antenna and a power source.

Antennas are located on the satellite and another one on Earth. The antennas on Earth, known as 'earth stations' are how people communicate to a satellite and is where the process begins. The earth station (or satellite dish if used with communication satellites) transmits information in the form of high powered, high frequency signals to the antenna on the satellite (called uplinks). The satellite then sends the same information back down to another transmitter on the Earth (called downlinks) to their coverage area. This area that receives signals from the satellite are known as the 'footprint' of the satellite. Spotbeams allow satellites to provide signals to a specific area.

The uplink/ downlink signals are radio waves (a form of electromagnetic radiation) that are nearly the same as FM and AM radio stations. The only difference is the frequency and wavelength of the signal. Radio wave frequencies range from around 3kHz (kilohertz) to 300GHz (gigahertz) and have corresponding wavelengths of 100km to 1mm that are determined by the speed of light. Satellite broadcasting uses Super High Frequency (SPF) and Extremely High Frequency (EHF) radio waves. All electromagnetic waves, including radio waves, produce transverse waves that vibrate perpendicular to the direction of the energy. The satellites are located in space which has an extremely little amount of matter, so these waves are used because they don't need a medium to travel through. They travel through what is known as a 'vacuum', which is a space devoid of matter. These types of waves carry no mass, only energy.

The satellite's radio frequencies are organized into several groups including amateur, meteorological, scientific and maritime. This is so specific satellites don't interfere with other radio communications.

The first artificial satellite, Sputnik 1, however, was not launched until October 4, 1957 by the Soviet Union. A month later the Soviet Union launched Sputnik 2 along with Laika, a dog, that is now known as the first living creature to escape Earth and enter outerspace. This created the 'space race' against the United Sates.
The United States quickly followed the led, launching their first satellite, Explorer 1, in February of 1958 which collected data about the radiation environment above Earth's surface (cosmic rays).
The first communication satellite was launched into space in December 1958, which broadcasted a Christmas message from President Eisenhower until the batteries failed twelve days later.
Sputnik 1- the first artificial satellite to be launched.
Modern- day satellites help everyone in their daily lives. They are used for a variety jobs including:
Television transmission: satellites send television signals directly to homes.
Telephone communications: satellites provide in-flight phone communications, communication for rural areas and primary timing source for mobile phones and pagers.

Navigation systems: satellites provide imagery of the Earth for the Global Positioning System (GPS) that allows people to determine their location. GPS's are commonly found in cars and on phones, being used by civilians and military for navigation on land, seas and air.

Weather reports: satellites provide meteorologists with information on weather patterns on a global scale.
Climate and environmental monitoring: satellites monitor ocean temperatures, water currents, measure the sizes of glaciers, rainfall patterns and emissions of greenhouse gases.
Land stewardship: satellites can detect underground water and mineral sources, as well as monitor large infrastructure.
Helps in business and finance: satellites provide video conferencing for international corporations, instant credit card authorization and automated teller banking services
Space science: provide vital information about space that any ground based research could not discover. They can watch for dangerous rays coming off the sun that may harm humans and provide information on asteroids and comets.

Development in countries: satellites provide developing countries with a range of education and medical information they would not usually receive.
There are now thousands of satellites orbiting the Earth.
Socrates, a Greek philosopher made the observation hundreds of years ago, "Man must rise above the Earth- to the top of the atmosphere and beyond- for only thus will he fully understand the world in which he lives."

Later in 1729, Isaac Newton published his cannonball thought experiment which explained how an object could get "to the top of the atmosphere". His thoughts included, "Add just the right amount of powder and impart just the right velocity to the ball, and it will travel completely around the planet, always falling in the gravitational field but never reaching the ground but it was a long time before one was created.

Arthur C. Clark is credited to be the first man to write about communication satellites. He published an article in 1945 titled 'Extra- Terrestrial Relays' in which he discussed earth orbit and the possibility of satellites.
Timeline of significant advancements in the first 20 years of satellite technology:
1957- first artificial satellite launched
1957- a satellite carrying radio and TV transmitters, scientific instruments and a dog, Laika, was launched
1958- the first recorded message was transmitted back to Earth
1960- first satellite that bounced radio signals back to Earth launched
1962- first commercial satellite launched into space. It carried the first transatlantic TV images and the first live satellite phone conversation
1964- first geostationary satellite launched
1964- the first live major sporting event (Tokyo Olympics) was transmitted via satellite around the world
1965- first commercial communications satellite to be placed in geosynchronous orbit. It was the first satellite to provide real-time transmission between Europe and North America, carrying TV, telephone and fax traffic.
1966- first Defense Satellite Communications Program was launched
1969- full global satellite communications coverage was achieved by Intelsat
1969- first moon landing was transmitted live by satellites
1969- first scientific satellite launched by NASA
1970- Japan launched their first satellite, making them the fourth country to do so after the USSR, USA and France
1972- first domestic communications satellite was launched
1975- Indian government began educational TV broadcasts to 5000 villages
1976- first Mobile Communications satellite launched

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- Brown, G. & Harris, W. (n.d.) ‘How Satellites Work,’ How Stuff Works, viewed 14 July 2014, from < http://science.howstuffworks.com/satellite.htm>
- Circuit Design Incorporated (n.d.) ‘What are Radio Waves,’ viewed 14 July 2014, from < http://www.cdt21.com/resources/guide2.asp>
- Cook, W. (1996) ‘How Do Satellites Work,’ William Craig Cook, viewed 13 July 2014, from <http://www.williamcraigcook.com/satellite/work.html>
- Federal Communications Commission (n.d.) ‘How Do Satellites Work,’ viewed 12 July 2014, from <http://transition.fcc.gov/cgb/kidszone/satellite/kidz/how_sats_work.html>
- Science Kids (2014) ‘Satellite Facts for Kids,’ viewed 13 July 2014, from < http://www.sciencekids.co.nz/sciencefacts/space/satellites.html>
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- Stillman, D. (2014) ‘What Is a Satellite,’ National Aeronautics and Space Administration, viewed 12 July, from < http://www.nasa.gov/audience/forstudents/5-8/features/what-is-a-satellite-58.html#.U7SeAfmSzX4>
- Tara, M. (1997) ‘Development of Satellites,’ St. Mary High School, viewed 12 July 2014, from <http://www.stmary.ws/highschool/physics/97/TMCDONOU.HTM>
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