Satellite

This article is about artificial satellites. For natural satellites, also known as moons, see

Satellites and Satalite redirect here. For the Canadian reggae band, see

For other uses, see

Early conceptions

The first fictional depiction of a satellite being launched into orbit is a by story is serialized in starting in 1869. The idea surfaces again in (1879).

In 1903 (1857–1935) published The Exploration of Cosmic Space by Means of Reaction Devices (in Исследование мировых пространств реактивными приборами), which is the first academic treatise on the use of rocketry to launch calculated the required for a minimal around the Earth at 8 km/s, and that a fueled by liquid could be used to achieve this. He proposed the use of and other combinations can be used.

In 1928 Slovenian (1892–1929) published his sole book, The Problem of Space Travel — The Rocket Motor (Das Problem der Befahrung des Weltraums — der Raketen-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 . He described the use of orbiting spacecraft for detailed peaceful and military observation of the ground and described how the special conditions of space couldn't be useful for scientific 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 the English science fiction writer (1917-2008) described in detail the possible use of for mass communications. Clarke examined the logistics of satellite launch, possible 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 satellites would provide coverage over the entire planet.

History of artificial satellites

Further information:

See also:

The first artificial satellite was , launched by the on 4 October 1957, and initiating the , with as chief designer and as his assistant. This in turn triggered the the and the

Sputnik 1 helped to identify the density of high through measurement of its orbital change and provided data on -signal distribution in the Because the satellite's body was filled with pressurized , Sputnik 1 also provided the first opportunity for 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 in the and ignited the so-called within the

was launched on November 3, 1957 and carried the first living passenger into orbit, a named

In May, 1946, had released the , 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 had been considering launching satellites since 1945 under the the . The '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 announced that the U.S. intended to launch satellites by the spring of 1958. This became known as . On July 31, the Soviets announced that they intended to launch a satellite by the fall of 1957.

Following pressure by the , the and the military interest picked up and in early 1955 the Air Force and Navy were working on which involved using a launch a satellite. The project succeeded, and became the United States' first satellite 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 catalog 115 Earth-orbiting satellites.

The largest artificial satellite currently orbiting the Earth is the

Space Surveillance Network

The (SSN) has been tracking space objects since 1957 when the Soviets opened the space age with the launch of Sputnik I. Since then, the SSN has tracked more than 26,000 space objects orbiting Earth. The SSN currently tracks more than 8,000 man-made orbiting objects. The rest have re-entered Earth's turbulent atmosphere and disintegrated, or survived re-entry and impacted the Earth. The space objects now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies weighing only 10 pounds. About seven percent of the space objects are operational satellites (i.e. ~560 satellites), the rest are primarily interested in the active satellites, but also tracks space debris which upon reentry might otherwise be mistaken for incoming missiles. The SSN tracks space objects that are 10 centimeters in diameter (baseball size) or larger.

Non-Military Satellite Services

There are three basic categories of non-military satellite services:

• are satellites that are armed, designed to take out enemy warheads, satellites, other space assets. They may have particle weapons, energy weapons, kinetic weapons, nuclear and/or conventional missiles and/or a combination of these weapons.
• are satellites used for observation of distant planets, galaxies, and other outer space objects.
• are satellites designed to carry living organisms, generally for scientific experimentation.
• are satellites stationed in space for the purpose of . Modern communications satellites typically use or
• are satellites of unusually low weights and small sizes. New classifications are used to categorize these satellites: minisatellite (500–200 kg), microsatellite (below 200 kg), nanosatellite (below 10 kg).
• are satellites which use 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 location to accuracies on the order of a few meters in real time.
• are or deployed for . Little is known about the full power of these satellites, as governments who operate them usually keep information pertaining to their reconnaissance satellites classified.
• are satellites intended for non-military uses such as monitoring, etc. (See especially
  
• are man-made structures that are designed for to live on in . A space station is distinguished from other manned its lack of major or — instead, other vehicles are used as transport to and from the station. Space stations are designed for medium-term living in for periods of , or even
• satellites which are connected to another satellite by a thin cable called a
  
• primarily used to monitor and