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