INTRO:
In the field of spaceflight, a satellite is an system which has been placed into orbit by human effort. Such objects are sometimes called synthetic/artificial satellites to differentiate them
from natural satellites such as the Celestial satellites(Moon for earth).The world's first artificial satellite, the Sputnik 1, was
launched by the Soviet Union in 1957. Since then, thousands
of satellites have been launched into orbit around the Earth.
Some satellites, notably space stations, have been launched
in parts and assembled in orbit. Artificial satellites originate
from more than 50 countries and have used the satellite
launching capabilities of ten nations. A few hundred satellites
are currently operational, whereas thousands of unused satellites and
satellite fragments orbit the Earth as space debris. A few space probes
have been placed into orbit around other bodies and become artificial
satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, and the
Sun.
PURPOSES:
Satellites are used for a huge variety of reasons. Common types include army and private World statement satellites, communications satellites, routing satellites, climate satellites, and research satellites.
Space channels and human spacecraft in orbit are also satellites.
Satellite orbits differ significantly, based on the purpose of the satellite,
and are categorized in various ways. Well-known (overlapping) classes consist of low World orbit, complete orbit, and geostationary orbit. Satellites are usually semi-independent computer-controlled systems. Satellite subsystems be present at many projects, such as power creation, thermal management, telemetry, mind-set management and orbit management.HISTORY:
The first artificial satellite was Sputnik 1, launched by the Soviet Union
on October 4, 1957, and initiating the Soviet Sputnik program, with
Sergei Korolev as chief designer (there is a crater on the lunar far side
which bears his name). This in turn triggered the Space Race between
the Soviet Union and the United States.
Sputnik 1 helped to identify the density of high atmospheric layers
through measurement of its orbital change and provided data on radiosignal
of Sputnik 1's success precipitated the Sputnik crisis in the United
States and ignited the so-called Space Race within the Cold War.
Sputnik 2 was launched on November 3, 1957 and carried the first
living passenger into orbit, a dog named Laika.
In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship,
which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent
scientific tools of the Twentieth Century." The United States had been considering launching orbital satellites since
1945 under the Bureau of Aeronautics of the United States Navy. The United States 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."
On July 29, 1955, the White House announced that the U.S. 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.
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 Army and Navy were working on Project
Orbiter, two competing programs: the army's which involved using a Jupiter C rocket, and the civilian/Navy
Vanguard Rocket, to launch a satellite. At first, they failed: initial preference was given to the Vanguard program,
whose first attempt at orbiting a satellite resulted in the explosion of the launch vehicle on national television. But
finally, three months after Sputnik 2, the project succeeded; Explorer 1 became the United States' first artificialsatellite on January 31, 1958.
In June 1961, three-and-a-half years after the launch of Sputnik 1, the Air Force used resources of the United States
Space Surveillance Network to catalog 115 Earth-orbiting satellites.
Early satellites were constructed as "one-off" designs. With growth in geosynchronous (GEO) satellite
communication, multiple satellites began to be built on single model platforms called satellite buses. The first
standardized satellite bus design was the HS-333 GEO commsat, launched in 1972.The largest artificial satellite currently orbiting the Earth is the International Space Station.
