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