| Introduction and Brief History of SatellitesA | | | | ionosphere. From 1946 to 1952, |
| satellite is any object that orbits another object | | | | upper-atmosphere research was conducted using |
| (which is known as its primary). All masses that | | | | V-2s and Aerobee rockets. This allowed |
| are part of the solar system, including the Earth, | | | | measurements of atmospheric pressure, density, |
| are satellites either of the Sun, or satellites of | | | | and temperature up to 200 km. The U.S. had |
| those objects, such as the Moon. It is not always | | | | been considering launching orbital satellites since |
| a simple matter to decide which is the 'satellite' in | | | | 1945 under the Bureau of Aeronautics of the |
| a pair of bodies. Because all objects exert gravity, | | | | United States Navy. The Air Force's Project |
| the motion of the primary object is also affected | | | | RAND eventually released the above report, but |
| by the satellite. If two objects are ufficiently | | | | did not believe that the satellite was a potential |
| similar in mass, they are generally referred to as | | | | military weapon; rather they considered it to be a |
| a binary system rather than a primary object and | | | | tool for science, politics, and propaganda. Following |
| satellite. The general criterion for an object to be | | | | pressure by the American Rocket Society, the |
| a satellite is that the center of mass of the two | | | | National Science Foundation, and the International |
| objects is inside the primary object. In popular | | | | Geophysical Year, military interest picked up and in |
| usage, the term 'satellite' normally refers to an | | | | early 1955 the Air Force and Navy were working |
| artificial satellite (a man-made object that orbits | | | | on Project Orbiter, which involved using a Jupiter |
| the Earth or another body).In May, 1946, the | | | | C rocket to launch a small satellite called Explorer |
| Preliminary Design of an Experimental | | | | 1 on January 31, 1958.On July 29, 1955, the White |
| World-Circling Spaceship stated, "A satellite vehicle | | | | House announced that the U.S. intended to launch |
| with appropriate instrumentation can be expected | | | | satellites by the spring of 1958. This became |
| to be one of the most potent scientific tools of | | | | known as Project Vanguard. On July 31, the |
| the Twentieth Century. The achievement of a | | | | Soviets announced that they intended to launch a |
| satellite craft would produce repercussions | | | | satellite by the fall of 1957 and on October 4, |
| comparable to the explosion of the atomic | | | | 1957 Sputnik I was launched into orbit, which |
| bomb..."The space age began in 1946, as scientists | | | | triggered the Space Race between the two |
| began using captured German V-2 rockets to | | | | nations.The largest artificial satellite currently |
| make measurements in the upper atmosphere. | | | | orbiting the earth is the International Space |
| Before this period, scientists used balloons that | | | | Station, which can sometimes be seen with the |
| went up to 30 km and radio waves to study the | | | | unaided human eye. |