How Satellites Work

"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."

Yerbolat AssylbekovBatyrbek AshirbayevProject2

Socrates made the observation centuries before humans successfully placed an object in Earth's orbit, even though he didn't know how to achieve it.

Isaac Newton published his now-famous cannonball thought experiment in 1729. His thinking went like this: Imagine you place a cannon atop a mountain and fire it horizontally. The cannonball will travel parallel to Earth's surface for a little while but will eventually succumb to gravity and fall to the ground. Keep adding gunpowder to the cannon. With the extra explosives, the cannonball will travel farther and farther before it falls. 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.

Early Observation

In October 1957, the Soviets finally proved Newton correct when they launched Sputnik 1 -- the first artificial satellite to orbit Earth.

Since Sputnik, several nations, led predominantly by the United States, Russia and China, have sent some 2,500 satellites into space

Kick-start

A satellite is any object that moves in a curved path around a planet. The moon is Earth's original, natural satellite, and there are many man-made (artificial) satellites, usually closer to Earth. The path a satellite follows is an orbit, which sometimes takes the shape of a circle.

Newton proposed that a force - gravity - exists between any two objects in the universe. If it weren't for this force, a satellite in motion near a planet would continue in motion at the same speed and in the same direction -- a straight line. This straight-line inertial path of a satellite, however, is balanced by a strong gravitational attraction directed toward the center of the planet.

What is satellite?

Sometimes, a satellite's orbit looks like an ellipse, a squashed circle that moves around two points known as foci

As a result, the net force applied to the satellite isn't uniform all the way around the orbit, and the speed of the satellite changes constantly. It moves fastest when it's closest to the planet -- a point known as perigee -- and slowest when it's farthest from the planet -- a point known as apogee.

Satellite cont’d

https://www.youtube.com/watch?v=54MSV2B399o

YouTube video explains

Three types of orbits used by satellites: Geostationary Orbit: In order to orbit the Earth in

24 hours, a satellite has to be placed in an orbit 22,237 miles above the Earth.

Highly-Elliptical Orbit: the satellite appears to slow down as it moves away from the Earth and speeds up as it approaches the Earth.

Low-Earth Orbit: A satellite in LEO travels at altitudes about three hundred to one thousand two-hundred and fifty miles above the Earth's surface.

Orbits

All of them have a metal or composite frame and body, usually known as the bus. The bus holds everything together in space and provides enough strength to survive the launch

All of them have a source of power (usually solar cells) and batteries for storage. Arrays of solar cells provide power to charge rechargeable batteries; also, they have onboard computer to control and monitor the different systems. Power on most satellites is precious and very limited. Nuclear power has been used on space probes to other planets.

All have a radio system and antenna. Most satellites have a radio transmitter/receiver, so that the ground-control crew can request status information from the satellite and monitor its health. Many satellites can be controlled in various ways from the ground to do anything from change the orbit to reprogram the computer system.

All of them have an attitude control system. The ACS keeps the satellite pointed in the right direction.

What's Inside a Typical Satellite?

A satellite is any object that revolves around a planet or smaller celestial body: moons as natural satellites, man-made objects like Sputnik and Expolorer.

Space Junk: 100m pieces of orbital debris no larger than 1 centimeter; 500,000 pieces in the 1-10 centimeter range and approximately 21,000 items larger than 10 centimeters

Orbital Debris are from: exploding rockets, the slip of an astronaut’s hand, jettisoned items.

Difference Between a Satellite and Space Junk

A rocket must accelerate to at least 40,320 kph to completely escape Earth's gravity and fly off into space

Orbital velocity is the velocity needed to achieve balance between gravity's pull on the satellite and the inertia of the satellite's motion -- the satellite's tendency to keep going.

This is approximately 27,359 kph at an altitude of 242 kilometers.

Without gravity, the satellite's inertia would carry it off into space.

The orbital velocity of the satellite depends on its altitude above Earth. At lower altitudes, a satellite runs into traces of Earth's atmosphere, which creates drag, which causes the orbit to decay until the satellite falls back into the atmosphere and burns up.

Orbital Velocity and Altitude

They often affect our lives without our realizing it: they make us safer, provide modern conveniences, and broadcast entertainment.

Television Telephones Navigation Business&Finance Weather (climate and environmental monitoring). Safety Land Stewardship Development Space Science

What are satellites used for?

It helped us to see the real examples of what the gravity is and it’s used in the modern world. The satellites are acted upon by the force of gravity and the force does accelerate it towards the Earth. Thanks to gravity, the satellites don’t fly away from our planet. Also, the satellites never fall on the Earth. the projectile will fall around the Earth, always accelerating towards it under the influence of gravity, yet never colliding into it since the Earth is constantly curving at the same rate. Such a projectile is an orbiting satellite.

What’s new for us, personally

Brown, G. How Satellite Works. Web. 4 Apr 2014. < http://www.physicsclassroom.com/mmedia/vectors/sat.cfm >

FCC.gov. How Satellites Work. < http://transition.fcc.gov/cgb/kidszone/satellite/kidz/leo.html >

The Physics Classroom: Satellite Motion. Web. 4 Apr 2014. http://www.physicsclassroom.com/mmedia/vectors/sat.cfm

Union of Concerned Scientists website.

YouTube video clip. < https://www.youtube.com/watch?v=54MSV2B399o >

Bibliography