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A satellite is an object that orbits another object (known as its primary). The term is often used to describe an artificial satellite (as opposed to natural satellites, or moons).
Because all objects exert gravity, the motion of the primary object is also affected by the satellite. (This observation allows for the discovery of extrasolar planets.) If two objects are sufficiently similar in mass, they are generally referred to as a binary system rather than a primary object and satellite. The general criterion for an object to be a satellite is that the center of mass of the two objects is inside the other object.
All masses that are part of the solar system, including the Earth, are satellites of the Sun, or satellites of those objects, such as the Moon.
In May, 1946, the Preliminary Design of an Experimental World-Circling Spaceship stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth CenturyCenturies: 19th century 20th century 21st century Decades: 1850s 1860s 1870s 1880s 1890s 1900s 1910s 1920s 1930s 1940s 1950s Years: 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 Events and Trends Technology Orville and Wilbur Wright make the first doc. The achievement of a satellite craft would produce repercussions comparable to the explosion of the atomic bomb..." (see: Project RAND)
The space age began in 1946 1The Radiation Belt and Magnetosphere is a book written by Wilmot Hess in 1968. The intention of the book is to amalgamate and sift through some 2500 articles, written since 1960, on this topic. See also: Magnetosphere, Van Allen radiation belt''., as scientists began using captured GermanThe Federal Republic of Germany ( German: Bundesrepublik Deutschland is one of the world's leading industrialized countries, located in the middle of the European Union. It is bordered to the north by the North Sea, Denmark and the Baltic Sea, to the east V-2 rocketThe V-2 rocket was an early ballistic missile used by Germany during the later stages of World War II against mostly British and Belgian targets. Pre-operational history As early as 1927 members of the German Rocket Society had started experimenting withs to make measurements in the upper atmosphere. Before this period, scientists could use ballooncards or flowers. A balloon is a flexible bag normally filled with air or gas. Some balloons are purely decorative, while others are used for specific purposes. Early balloons were made of dried animal bladders. Balloons as flying machines Large balloonss up to 30 km and radio waves to study the ionosphere; rockets changed that. From 1946 to 1952, upper-atmosphere research was conducted using V-2s and Aerobee rockets. This allowed measurements of atmospheric pressure, density, and temperature up to 200 km. (see also: magnetosphere, Van Allen radiation belt)
The U.S. had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The Air Force's Project RAND eventually released the above report, but did not believe that the satellite was a potential military weapon; rather they considered it to be a tool for science, politics, and propaganda. In 1954, the Secretary of Defense stated, "I know of no American satellite program."
Following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, military interest picked up and in early 1955 the Air Force and Navy were working on Project Orbiter, which involved using a Jupiter C rocket to launch a small satellite called Explorer 1 on January 31, 1958.
On July 29, 1955, the White House announced that the US intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On July 31, the Soviets announced that they intended to launch a satellite by the fall of 1957 and on October 4, 1957 Sputnik I was launched into orbit, which triggered the Space Race between the two nations.