(Redirected from Artificial satellite)
An Earth observation satellite,
ERS 2
In the context of
spaceflight, 'satellites' are objects which have been placed into
orbit by human endeavor. They are sometimes called 'artificial satellites' to distinguish them from
natural satellites such as the
Moon.
Early theoretical work on artificial satellites
The first known fictional depiction 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'', 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 is the first academic treatise on the use of rocketry to launch
spacecraft. He calculated the
orbital speed required for a minimal
orbit around the Earth at 8 km/second, 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 can be used. During his lifetime he published over 500 works on space travel and related subjects, including science fiction novels. Among his works are designs for rockets with steering thrusters, multi-stage boosters, space stations, airlocks for exiting a spaceship into the vacuum of space, and closed cycle biological systems to provide food and oxygen for space colonies. He also delved into theories of heavier-than-air flying machines, independently working through many of the same calculations that the
Wright brothers were performing at about the same time.
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 how the special conditions of space could 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 ''
Wireless World'' article the English science fiction writer
Arthur C. Clarke (b. 1917) 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.
History of artificial satellites
The first artificial satellite was
Sputnik 1, launched by the
Soviet Union on
4 October 1957. This triggered the
Space Race between the Soviet Union and the
United States.
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.
[4]
The
United States 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."
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 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.
The largest artificial satellite currently orbiting the Earth is the
International Space Station.
Space Surveillance Network
The
United States Space Surveillance Network (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
space debris.
USSTRATCOM is 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.
Types
★ '
Anti-Satellite weapons', sometimes called "Killer satellites" are satellites designed to destroy "enemy" satellites, other orbital weapons and targets. Some are armed with kinetic rounds, while others use energy and/or particle weapons to destroy satellites, ICBMs, MIRVs. Both the U.S. and the USSR had these satellites. Links discussing "Killer satellites", ASATS (Anti-Satellite satellite) include
USSR Tests ASAT weapon and
ASAT Test. See also
IMINT
★ '
Astronomical satellites' are satellites used for observation of distant planets, galaxies, and other outer space objects.
★ '
Biosatellites' are satellites designed to carry living organisms, generally for scientific experimentation.
★ '
Communications satellites' are satellites stationed in space for the purpose of
telecommunications. Modern communications satellites typically use
geosynchronous orbits,
Molniya orbits 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 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 location to accuracies on the order of a few metres 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.
★ '
Earth observation satellites' are satellites intended for non-military uses such as
environmental monitoring,
meteorology,
map making etc. (See especially
Earth Observing System.)
★ '
Solar power satellites' are proposed satellites built in
high Earth orbit that use
microwave power transmission to beam
solar power to very large
antennae on Earth where it can be used in place of conventional power sources.
★ '
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 or
landing facilities — instead, other vehicles are used as transport to and from the station. Space stations are designed for medium-term living in
orbit, for periods of
weeks,
months, or even
years.
★ '
Weather satellites' are satellites that primarily are used to monitor
Earth's
weather and
climate.
Orbit types
Main articles: List of orbits
Centric classifications
:'
Galacto-centric Orbit' - An orbit about the center of a
galaxy.
Earth's
sun follows this type of orbit about the
galactic center of the
Milky Way.
:'
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.
:'
Geocentric Orbit' - An orbit around the planet
Earth, such as the
Moon or
artificial satellites. Currently there are approximately 2465 artificial satellites orbiting the
Earth.
:'
Areocentric Orbit' - An orbit around the planet
Mars, such as
moons or
artificial satellites.
Altitude classifications
:'
Low Earth Orbit (LEO)' -
Geocentric orbits ranging in altitude from 0 - 2,000
km (0 - 1,240
miles)
:'
Medium Earth Orbit (MEO)' -
Geocentric orbits ranging in altitude from 2,000
km (1,240
miles) - to just below
geosynchronous orbit at 35,786
km (22,240
miles). Also known as an
intermediate circular orbit.
:'
High Earth Orbit (HEO)' -
Geocentric orbits above the altitude of
geosynchronous orbit 35,786
km (22,240
miles).
Inclination classifications
:'
Inclined Orbit' - An orbit whose
inclination in reference to the
equatorial plane is not 0.
::'
Polar Orbit' - An
orbit that passes above or nearly above both poles of the planet on each revolution. Therefore it has an
inclination of (or very close to) 90
degrees.
::'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 the same on every pass.
Eccentricity classifications
:'
Circular Orbit' - An
orbit that has an
eccentricity of 0 and whose path traces a
circle.
::'
Hohmann transfer orbit' - An orbital maneuver that moves a
spacecraft from one
circular orbit to another using two engine
impulses. This maneuver was named after
Walter Hohmann.
:'
Elliptic Orbit' - An
orbit with an
eccentricity greater than 0 and less than 1 whose orbit traces the path of an
ellipse.
::'
Geosynchronous Transfer Orbit' - An
elliptic orbit where the
perigee is at the
altitude of a
Low Earth Orbit (LEO) and the
apogee at the
altitude of a
geosynchronous orbit.
::'
Geostationary Transfer Orbit' - An
elliptic orbit where the
perigee is at the
altitude of a
Low Earth Orbit (LEO) and the
apogee at the
altitude of a
geostationary orbit.
::'
Molniya Orbit' - A highly
elliptic orbit with
inclination of 63.4° and
orbital period of ½ 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 a
hyperbolic orbit.
::'
Escape Orbit (EO)' - A high-speed
parabolic orbit where the object has
escape velocity and is moving away from the
planet.
::'
Capture Orbit' - A high-speed
parabolic orbit where the object has
escape velocity and is moving toward the
planet.
Synchronous classifications
:'
Synchronous Orbit' - An orbit where the satellite has an
orbital period equal to the average
rotational period (earth's is: 23
hours, 56
minutes, 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 20,200 km (12544.2 miles) and an
orbital period of approximately 12 hours
:'
Geosynchronous Orbit (GEO)' - Orbits with an altitude of approximately 35,786 km (22,240 miles). Such a satellite would trace an
analemma (figure 8) in the sky.
:::'
Geostationary orbit (GSO)': A
geosynchronous orbit with an
inclination of zero. To an observer on the ground this satellite would appear as a fixed point in the sky.
::'
Clarke Orbit' - Another name for a
geostationary orbit. Named after the writer
Arthur C. Clarke.
::'
Supersynchronous orbit' - A disposal / storage orbit above GSO/GEO. Satellites will drift west. Also a
synonym for
Disposal Orbit.
::'
Subsynchronous orbit' - A drift orbit close to but below GSO/GEO. Satellites will drift east.
::'
Graveyard Orbit' - An orbit a few hundred kilometers above
geosynchronous that satellites are moved into at the end of their operation.
:::'
Disposal Orbit' - A
synonym for
graveyard orbit.
:::'
Junk Orbit' - A
synonym for
graveyard orbit.
:'
Areosynchronous Orbit' - A
synchronous orbit around the planet
Mars with an
orbital period equal in length to Mars'
sidereal day, 24.6229
hours.
:'
Areostationary Orbit (ASO)' - A
circular areosynchronous orbit on the
equatorial plane and about 17,000
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 the
Sun, a little less than half of the
orbital radius of
Mercury.
Special classifications
:'
Sun-synchronous Orbit' - An orbit which combines
altitude and
inclination in such a way that the satellite passes over any given point of the
planets's surface at the same local
solar time. Such an orbit can place a satellite in constant sunlight and is useful for
imaging,
spy, and
weather satellites.
:'
Moon Orbit' - The
orbital characteristics of
earth's
moon. Average
altitude of 384,403 kilometres (238,857 mi),
elliptical-
inclined orbit.
'Pseudo-Orbit Classifications'
:'
Horseshoe Orbit' - An
orbit that appears to a ground observer to be orbiting a certain
planet but is actually in
co-orbit with the
planet. See asteroids
3753 (Cruithne) and
2002 AA29.
:'
Exo-orbit' - A maneuver where a
spacecraft approaches the height of
orbit but lacks the
velocity to sustain it.
::'
Orbital Spaceflight' - A
synonym for
exo-orbit.
:'
Lunar transfer orbit (LTO)' -
:'
Prograde Orbit' - An
orbit with an inclination of less than 90°. Or rather, an orbit that is in the same direction as the rotation of the primary.
:'
Retrograde orbit' - An
orbit with an
inclination of more than 90°. Or rather, an orbit counter to the direction of rotation of the planet. Apart from those in
sun-synchronous orbit, few satellites are launched into
retrograde orbit because the quantity of fuel required to launch them is much greater than for a
prograde orbit. This is because when the rocket starts out on the ground, it already has an eastward component of
velocity equal to the rotational velocity of the planet at its launch
latitude.
Satellites can also orbit
Lagrangian Points.
Launch-capable countries
Main articles: Timeline of first orbital launches by nationality
This list includes countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle. Note: many more countries have the capability to design and build satellites — which relatively speaking, does not require much economic, scientific and industrial capacity — but are unable to launch them, instead relying on foreign launch services. This list 'does not' consider those numerous countries, but only lists those capable of launching satellites indigenously, and the date this capability was first demonstrated. Does not include consortium satellites or multi-national satellites.
Both
North Korea (
1998) and
Iraq (
1989) have claimed orbital launches, but these claims are unconfirmed.
Other countries, such as
South Africa,
Spain,
Italy,
West Germany,
Canada,
Australia,
Argentina,
Egypt, and private companies such as
OTRAG, have developed their own launchers, but have not had a successful launch.
As of 2007, only 7 countries from list above (six 'major' -
Russia and
Ukraine instead of
USSR, also
USA,
Japan,
China,
India, and 1 'minor' -
Israel) and one regional organisation (the
European Union, represented by
European Space Agency (ESA)) have independently launched satellites on their own indigenously developed launch vehicles. (The launch capabilities of the
United Kingdom and
France now fall under the
ESA.)
Also, one international private company (
Sea Launch) has launch capability through their purchase of Ukrainian-Russian launchers.
Several other countries, including
Brazil,
Iran,
South Korea,
Malaysia,
Pakistan, and
Turkey, are at various stages of development of their own small-scale launcher capabilities, and seek membership in the club of space powers.
While
Canada was the third country to build a satellite which was launched into Space, it was launched aboard a U.S. rocket from a U.S. spaceport. The same goes for
Australia, who launched on-board a donated Redstone rocket. The first Italian-launched was
San Marco 1, launched on
15 December,
1964 on a U.S.
Scout rocket from Wallops Island (VA,USA) with an Italian Launch Team trained by NASA.
[3].
Australia's launch project, in November 1967, involved a donated U.S. missile and U. S. support staff as well as a joint launch facility with the
United Kingdom.
[4]
Kazakhstan claimed to have launched their satellite independently, but the satellite was built with Russian help.
Heraldry
The (artificial, though this is not stated in the blazon) satellite appears as a
charge in the arms of
Arthur Maxwell House.
[5] This is in addition to numerous appearances of the natural satellite the
moon, and the moons of the
planets
Jupiter and
Saturn (with those planets) in the arms of
Pierre-Simon LaPlace.
See also
A model satellite in a museum
★
Communications satellite
★
Timeline of artificial satellites and space probes
★
List of Earth observation satellites
★
International Designator
★
Satellite Catalog Number
★
Miniaturized satellite
★
Satellite formation flying
★ Satellites (sorted by launch date):
★
★
Syncom 1 (
1963), 2 (1963) and 3 (1964)
★
★
Anik 1 (1972)
★
★
EgyptSat 1 (2007) (Egypt, launched by Ukraine)
★
★
Aryabhata (1975) (India, launched by USSR)
★
★
Hermes Communications Technology Satellite (1976)
★
★
Experimental geodetic payload (1986)
★
★
Munin (2000) (Sweden, launched by U.S.)
★
★
KEO satellite - a space
time capsule (2006)
★ Satellite Services:
★
★
Satellite phone
★
★
Satellite Internet
★
★
Satellite television
★
★
Satellite radio
★
Anti-satellite weapon
★
GoldenEye (fictional satellite weapon)
★
Tether satellite
References
1.
The Brick Moon and Other Stories by Edward Everett Hale
2.
Contents - The Atlantic monthly. Volume 24, Issue 141
3. facsimile at http://www.lsi.usp.br/~rbianchi/clarke/ACC.ETRelaysFull.html
4.
Preliminary Design of an Experimental World-Circling Spaceship
5. http://heraldry.ca/arms/h/house.htm
★
External links
★
Satellite Ground Tracks Real time satellite's tracks (Full catalog of satellite orbit). (deutsch) (portugues)
★
'Eyes in the Sky' Free video by the Vega Science Trust and the BBC/OUSatellites and their implications over the last 50 years.
★
How Stuff Works.com How satellites work
★
UCS Satellite Database Lists operational satellites currently in orbit around the Earth. Updated quarterly.
★
Edusat project
★
Facsimile of Arthur C. Clarke's 1945 paper on communication satellites
★
UN Office for Outer Space Affairs ensures all countries benefit from satellites
★
CBC Digital Archives - Launching the Digital Age: Canadian Satellites
★
'Student Satellite Project' Student Satellite Project for Pakistani and International Students. This site contains information and documents about satellite projects.
★
NASA Orbital Debris Program Office
'
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