Artificial Satellites Brief introductionIn the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.Facts & historyWhat was the first artificial satellite constructed by humans?Sputnik 1• First satellite to be launched in space by the Soviet Union in 1957. • Triggered the space race during the Cold war era. • Initially the united states thought the satellite could be used as a weapon. Facts & historyWhat is the most recent artificial satellite launched by humans?Juno, launched by the USA in 2011 to JupiterFunctions of satellites• Every artificial satellite has distinct features to help it to better perform its jobs. For example, satellites that study the universe contain a telescope, and satellites that determine and predict the weather include cameras to help observe cloud movement. • Some Artificial Satellites gather information about our universe for NASA and other organizations. In addition, some Artificial Satellites help to connect people worldwide by assisting in telephone calls over the ocean. • So artificial satellites all have different functions depending on what their job is. Different types of satellites• Military and civilian earth observation satellite, • Communications satellite(COMSAT), • Navigation satellite, • Weather satellite and research satellite*Space stations and human spacecraft in orbit are also satellites.Orbits of satellites• Low Earth orbit(LEO)An orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. • Polar orbitAn orbit that satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth) on each revolution. It therefore has an inclination of (or very close to) 90 degrees to the equator. • Geostationary orbit(GEO)A geosynchronous orbit directly above the Earth's equator (0° latitude), with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers. How do scientists make use of Kepler’s laws and Newton’s universal law of gravitation when launching artificial satellites?• Newton's Universal Law of Gravity: FGravity = G msmEarth/r2 The force of gravity equals the gravitational constant times the mass of the satellite times the mass of the earth divided by the square of the distance between the satellite and the earth.• Kepler's 2nd law:A line joining a [satellite] and the [planet] sweeps out equal areas during equal intervals of time. This explains how the satellite moves and that it moves faster when closer to the planet it is orbiting (Earth).How Do Satellites Work?http://youtu.be/54MSV2B399o?t=1m1s。
