In the context of spaceflight, a satellite is an object that has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon .
Satellites are useful budget car rental sales for a number of purposes. They are used for communications, navigation, map-making, astronomical observations, scientific experimentation, and monitoring of the Earth's environment and weather conditions. Some satellites with military missions may conduct espionage or carry weapons to destroy enemy warheads and satellites.
The first fictional depiction budget car rental sales of a satellite being launched into orbit is a short story by Edward Everett Hale, The Brick Moon. The story was serialized in The Atlantic Monthly, budget car rental sales starting in 1869. [1] [2] The idea surfaces again in Jules Verne 's The Begum's Millions (1879).
In 1903, Konstantin Tsiolkovsky (1857–1935) published Исследование мировых пространств реактивными приборами (The Exploration of Cosmic Space by Means of Reaction Devices), which was the first academic treatise on the use of rocketry to launch spacecraft . He calculated the orbital budget car rental sales speed required for a minimal orbit around the Earth at 8 km/s, and that a multi-stage rocket fueled by liquid propellants could be used to achieve this. He proposed the use of liquid hydrogen and liquid oxygen, though other combinations could be used.
In 1928, Herman Potočnik (1892–1929) published his sole book, Das Problem der Befahrung des Weltraums - der Raketen-Motor (The Problem of Space Travel—The Rocket Motor), a plan for a breakthrough into space and a permanent human presence there. He conceived of a space station in detail and calculated its geostationary orbit. He described the use of orbiting spacecraft for detailed peaceful and military observation of the ground and described budget car rental sales how the special conditions of space could be useful for scientific budget car rental sales experiments. The book described geostationary satellites (first put forward by Tsiolkovsky) and discussed communication between them and the ground using radio, but fell short of the idea of using satellites for mass broadcasting and as telecommunications relays.
In a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke (1917-2008) described in detail the possible use of communications satellites for mass communications. [3] Clarke examined the logistics of satellite launch, possible orbits , and other aspects of the creation of a network of world-circling satellites, pointing to the benefits of high-speed global communications. He also suggested that three geostationary satellites would provide coverage over the entire planet.
budget car rental sales The first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957, and that started the whole Soviet Sputnik program, with Sergei Korolev as chief designer. This triggered budget car rental sales the Space Race between the Soviet Union and the United budget car rental sales States .
Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio -signal distribution in the ionosphere. Because the satellite's body was filled with pressurized nitrogen , Sputnik 1 also provided the first opportunity for meteoroid detection, as a loss of internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data sent back to Earth. The unanticipated announcement of Sputnik 1' s success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War .
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. [5] The United budget car rental sales States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The United budget car rental sales States Air Force's Project RAND eventually released the above report, but did not believe that the satellite budget car rental sales was a potential military weapon; rather, they considered it to be a tool for science, politics, and propaganda.
On July 29, 1955, the White House announced budget car rental sales that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On July 31, the Soviets budget car rental sales 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 Air Force and Navy were working on Project Orbiter, which involved using a Jupiter C rocket to launch a satellite. The project succeeded, and Explorer 1 became the United States' first satellite on January 31, 1958. [6]
Communications satellites are satellites stationed in space for the purpose of telecommunications . Modern communications satellites typically use geosynchronous orbits, Molniya orbits, budget car rental sales or Low Earth orbits.
Miniaturized satellites are satellites of unusually low weights and small sizes. New classifications are used to categorize these satellites: minisatellite (500–200 kg), microsatellite (below budget car rental sales 200 kg), nanosatellite (below 10 kg).
Navigational satellites are satellites which use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure budget car rental sales location to accuracies on the order of a few meters in real time.
Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications. Little is known about the full power of these satellites, as governments who operate them usually keep information pertaining to their reconnaissance satellites classified.
Space stations are man-made structures that are designed for human beings to live on in outer space . A space station is distinguished from other manned spacecraft by its lack of major propulsion budget car rental sales or landing facilities—instead, other vehicles are used as transport to and from the station. Space stations budget car rental sales are designed for medium-term living in orbit , for periods of weeks, months, or even years .
Various earth orbits to scale; cyan represents low earth orbit, yellow represents medium earth orbit, the black dashed line represents geosynchronous orbit, the green dash-dot line the orbit of Global Positioning System (GPS) satellites, and the red dotted line the orbit of the International Space Station (ISS).
The first satellite, Sputnik 1, was put into orbit around Earth and was therefore in geocentric orbit. By far this is the most common type of orbit with approximately 2456 artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and eccentricity.
The commonly used altitude classifications are Low Earth Orbit (LEO), budget car rental sales Medium Earth Orbit (MEO) and High Earth Orbit (HEO). Low Earth orbit is any orbit below 2000 km, and Medium Earth Orbit is any orbit higher than that but still below the altitude for geosynchronous orbit at 35786 km. High Earth Orbit is any orbit higher than the altitude for geosynchronous orbit.
Heliocentric orbit : An orbit around the Sun . In our Solar System , all planets, comets , and asteroids are in such orbits, as are many artificial satellites and pieces of space debris . Moons by contrast are not in a heliocentric orbit but rather orbit their parent planet.
Medium Earth Orbit (MEO) : Geocentric orbits ranging in altitude from 2000 km (1240 miles ) to just below geosynchronous orbit at 35786 km (22240 miles). Also known as an intermediate circular orbit.
Polar sun synchronous orbit : A nearly polar orbit that passes the equator at the same local time on every pass. Useful for image taking satellites because shadows will be nearly the same on every pass.
Molniya budget car rental sales orbit : A highly elliptic budget car rental sales orbit with inclination of 63.4° and orbital period of half of a sidereal day (roughly 12 hours). Such a satellite spends most of its time over a designated area of the planet .
Tundra orbit : A highly elliptic orbit with inclination of 63.4° and orbital period of one sidereal day (roughly 24 hours). Such a satellite spends most of its time over a designated area of the planet .
Hyperbolic orbit : An orbit with the eccentricity greater than 1. Such an orbit also has a velocity in excess of the escape velocity and as such, will escape the gravitational pull of the planet and continue to travel infinitely.
Parabolic orbit : An orbit with the eccentricity equal to 1. Such an orbit also has a velocity equal to the escape velocity and therefore will escape the gravitational pull of the planet and travel until its velocity relative to the planet is 0. If the speed of such an orbit is increased it will become budget car rental sales a hyperbolic orbit.
Synchronous orbit : An orbit where the satellite has an orbital period equal to the average rotational period (earth's is: 23 hours, 56 minutes, budget car rental sales 4.091 seconds ) of the body being orbited and in the same direction of rotation as that body. To a ground observer such a satellite would trace an analemma (figure 8) in the sky.
Semi-synchronous orbit (SSO) : An orbit with an altitude of approximately 20200 km (12544.2 miles) and an orbital period equal to one-half of the average rotational period (earth's is approximately 12 hours) of the body being orbited
Areostationary orbit (ASO) : A circular areosynchronous orbit on the equatorial plane and about 17000 km(10557 miles ) above the surface. To an observer on the ground this satellite would appear as a fixed point in the sky.
Heliosynchronous orbit : An heliocentric orbit about the Sun where the satellite's orbital period matches the Sun's period of rotation. These orbits occur at a radius of 24,360 Gm (0,1628 AU) around th
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