Our Eyes in the Sky
When asked what the most important object today is, most people would probably say “smartphones” or “computers” or “ice cream.” While these may be important, they are definitely not the most important. By far, satellites are the most important objects today. Most everything, including smartphones and computers, are present today because of satellites and have capabilities such as Wi-Fi and 4G because of the role satellites play. Even Socrates, who lived centuries before the first satellite, realized the importance of a view from space when he said, "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."
According to NASA, 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. Thousands of artificial, or man-made, satellites orbit Earth. Some take pictures of the planet that help meteorologists predict weather and track hurricanes. Others are used to connect various devices such as computers, TV’s, and phones. Still others provide internet and GPS. There are even some that are used as spy satellites and weapons against other countries. The bird’s-eye view 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. Additionally, satellites don’t have to deal with interference from Earth’s atmosphere because they orbit earth in space outside of the atmosphere. Because of this, satellites can see into space much better than telescopes at Earth’s surface.
A satellite works by receiving radio signals sent from the Earth and resending the radio signals back down to the Earth. In a simple system, a signal is reflected, or "bounced," off the satellite. For example, it is possible to bounce a signal off the surface of the Moon back down to Earth. However, because the Moon is so far away, for this to work, the signal from Earth must be very strong and the receiver receiving the signal must be sensitive enough to detect the very weak signal coming back from the moon. Unlike a passive satellite such as the moon or early satellites, a modern communications satellite receives the radio signal and sends it back down to Earth stronger than it was received. This process is called an amplification of the radio signal. In addition to amplifying the signal, a communications satellite also typically converts the radio from one frequency to another so that the signal getting sent down is not confused with the signal being sent up.
There are two main types of satellites: Geostationary and polar. A geostationary satellite travels from west to east over the equator. It moves in the same direction and at the same rate Earth is spinning. From Earth, a geostationary satellite looks like it is standing still because it is always above the same location in relation to Earth. Polar satellites travel in a north-south direction from pole to pole. As Earth spins, polar satellites can scan the entire globe.
As of October 2013, there are about 1,071 operational satellites orbiting the Earth. 50% of these were launched by the US. As of January 2013, there are about 13 countries that have the capability to launch satellites. These include Russia, the US, France, Japan, China, the UK, India, Israel, Ukraine, Iran, North Korea, and South Korea. Satellites are usually taken into orbit by rockets or space craft. Most satellites are expected to have a 10 year life span. After this life span, they are taken out of orbit by usually being propelled into space. Like all things, there are exceptions to this. Some satellites last more than 10 years, and some last barely one year before...
Please join StudyMode to read the full document