Early conceptions
"
Newton's cannonball", presented as a "thought experiment" in
A Treatise of the System of the World, was the first published mathematical study of the possibility of an artificial satellite.
In 1903,
Konstantin Tsiolkovsky (1857–1935) published
Means of Reaction Devices (in
Russian:
Исследование мировых пространств реактивными приборами), which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the
orbital speedrequired 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 can be used.
In 1928 Slovenian
Herman Potočnik (1892–1929) published his sole book,
The Problem of Space Travel — The Rocket Motor (
German:
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 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 (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.
The US military studied the idea of what was referred to as the
earth satellite vehicle when Secretary of Defense, James Forrestal, made a public announcement on December 29, 1948 that his office was coordinating that project between the various services.
[4]
[edit]History of artificial satellites
Sputnik 1: The first artificial satellite to orbit Earth.
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 layersthrough measurement of its orbital change and provided data on radio-signal distribution in the
ionosphere. The unanticipated announcement of
Sputnik 1's success precipitated the
Sputnik crisis in the United States and ignited the so-called
Space Racewithin the
Cold War.
Sputnik 2 was launched on November 3, 1957 and carried the first living passenger into orbit, a dog named
Laika.
[5]
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."
[6] 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."
[7]
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 artificial satellite on January 31, 1958.
[8]
[edit]Space Surveillance Network
The United States Space Surveillance Network (
SSN), a division of
The United States Strategic Command, has been tracking objects in Earth's orbit 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 objects. The SSN currently tracks more than 8,000 man-made orbiting objects. The rest have re-entered Earth's atmosphere and disintegrated, or survived re-entry and impacted the Earth. The SSN tracks objects that are 10 centimeters in diameter or larger; those now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies weighing only 10 pounds. About seven percent are operational satellites (i.e. ~560 satellites), the rest are
space debris.
[10] The United States Strategic Command is primarily interested in the active satellites, but also tracks space debris which upon reentry might otherwise be mistaken for incoming missiles.
A search of the
NSSDC Master Catalog at the end of October 2010 listed 6,578 satellites launched into orbit since 1957, the latest being
Chang'e 2, on 1 October 2010.
[11]
[edit]Non-military satellite services
There are three basic categories of non-military satellite services:
[12]
[edit]Fixed satellite services
Fixed satellite services handle hundreds of billions of voice, data, and video transmission tasks across all countries and continents between certain points on the Earth's surface.
[edit]Mobile satellite systems
Mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to other parts of the world and/or other mobile or stationary communications units, in addition to serving as navigation systems.
[edit]Scientific research satellites (commercial and noncommercial)
Scientific research satellites provide us with meteorological information, land survey data (e.g remote sensing), Amateur (HAM) Radio, and other different scientific research applications such as earth science, marine science, and atmospheric research.
- Anti-Satellite weapons/"Killer Satellites" are satellites that are designed to destroy enemy warheads, satellites, and other space assets.
- 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 orLow Earth orbits.
- Miniaturized satellites are satellites of unusually low masses and small sizes.[13] New classifications are used to categorize these satellites: minisatellite (500–100 kg),microsatellite (below 100 kg), nanosatellite (below 10 kg).[citation needed]
- 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 meters in real time.
- Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military orintelligence applications. Very 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.)
- Tether satellites are satellites which are connected to another satellite by a thin cable called a tether.
- Weather satellites are primarily used to monitor Earth's weather and climate.[14]
- Recovery satellites are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth.
- Manned spacecraft (spaceships) are large satellites able for put human into (and beyond) an orbit, being on it and recovery back to Earth. Spacecrafts, and orbital parts-spaceplanes of reusable systems also, has a major propulsion or landing facilities, and often uses as transport to and from the orbital stations.
- Space stations are man-made orbital 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. Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years.
[edit]Orbit types
Main article:
List of orbits
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),
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.
[edit]Centric classifications
The general structure of a satellite is that it is connected to the earth stations that are present on the ground and connected through terrestrial links.
[edit]Altitude classifications
- Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0–2000 km (0–1240 miles)
- Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2,000 km (1,200 mi) to just below geosynchronous orbit at 35,786 km (22,236 mi). Also known as an intermediate circular orbit.
- High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,236 mi).
Orbital Altitudes of several significant satellites of earth.
[edit]Inclination classifications
- Inclined orbit: An orbit whose inclination in reference to theequatorial plane is not zero degrees.
- 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 nearly the same on every pass.
[edit]Eccentricity classifications
- Circular orbit: An orbit that has an eccentricity of 0 and whose path traces a circle.
- Elliptic orbit: An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of anellipse.
- 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 half of a sidereal day(roughly 12 hours). Such a satellite spends most of its time over two designated areas of the planet(specifically Russia and the United States).
- 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 single designated area of the planet.
[edit]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 (12,600 mi) and an orbital period equal to one-half of the average rotational period (earth's is approximately 12 hours) of the body being orbited
- Geosynchronous orbit (GSO): Orbits with an altitude of approximately 35,786 km (22,236 mi). Such a satellite would trace an analemma (figure 8) in the sky.
- Geostationary orbit (GEO): 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.[15]
- 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.
- 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 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: A 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.
[edit]Special classifications
[edit]Pseudo-orbit classifications
- Horseshoe orbit: An orbit that appears to a ground observer to be orbiting a certain planet but is actually inco-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.
- 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.
- Halo orbit and Lissajous orbit: Orbits "around" Lagrangian points.
[edit]Satellite subsystems
The satellite's functional versatility is imbedded within its technical components and its operations characteristics. Looking at the "anatomy" of a typical satellite, one discovers two modules.
[12] Note that some novel architectural concepts such as
Fractionated Spacecraft somewhat upset this taxonomy.
[edit]Spacecraft bus or service module
This
bus module consist of the following subsystems:
- The Structural Subsystems
The structural subsystem provides the mechanical base structure, shields the satellite from extreme temperature changes and micro-meteorite damage, and controls the satellite's spin functions.
- The Telemetry Subsystems (aka Command and Data Handling, C&DH)
The telemetry subsystem monitors the on-board equipment operations, transmits equipment operation data to the earth control station, and receives the earth control station's commands to perform equipment operation adjustments.
The power subsystem consists of solar panels and backup batteries that generate power when the satellite passes into the Earth's shadow. Nuclear power sources (
Radioisotope thermoelectric generators) have been used in several successful satellite programs including the
Nimbus program (1964–1978).
[16]
- The Thermal Control Subsystems
The thermal control subsystem helps protect electronic equipment from extreme temperatures due to intense sunlight or the lack of sun exposure on different sides of the satellite's body (e.g.
Optical Solar Reflector)
- The Attitude and Orbit Control Subsystems
The attitude and orbit control subsystem consists of small rocket thrusters that keep the satellite in the correct orbital position and keep antennas positioning in the right directions.
[edit]Communication payload
The second major module is the communication payload, which is made up of transponders. A transponder is capable of :
- Receiving uplinked radio signals from earth satellite transmission stations (antennas).
- Amplifying received radio signals
- Sorting the input signals and directing the output signals through input/output signal multiplexers to the proper downlink antennas for retransmission to earth satellite receiving stations (antennas).
[edit]End of life
When satellites reach the end of their mission, satellite operators have the option of de-orbiting the satellite, leaving the satellite in its current orbit or moving the satellite to a graveyard orbit. Historically, due to budgetary constraints at the beginning of satellite missions, satellites were rarely designed to be de-orbited. One example of this practice is the satellite
Vanguard 1. Launched in 1958,
Vanguard 1, the 4th manmade satellite put in Geocentric orbit, was still in orbit as of August 2009.
[17]
Instead of being de-orbited, most satellites are either left in their current orbit or moved to a
graveyard orbit.
[18] As of 2002, the FCC now requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch.
[19]
[edit]Launch-capable countries
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 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.
[edit]Attempted first launches
- United States tried in 1957 to launch the first satellite by own launcher before successfully completing a launch in 1958.
- China tried in 1969 to launch the first satellite by own launcher before successfully completing a launch in 1970.
- India, after launching the first national satellite by foreign launcher in 1975, tried in 1979 to launch the first satellite by own launcher before succeeding in 1980.
- Iraq have claimed orbital launch of warhead in 1989, but this claim was later disproved.[23]
- Brazil, after launch of first national satellite by foreign launcher in 1985, tried to launched the satellites by ownVLS 1 launcher three times in 1997, 1999, 2003 but all were unsuccessful.
- North Korea claimed a launch of Kwangmyŏngsŏng-1 and Kwangmyŏngsŏng-2 satellites in 1998 and 2009, but U.S., Russian and other officials and weapons experts later reported that the rockets failed to send a satellites into orbit, if that was the goal. The United States, Japan and South Korea believe this was actually a ballistic missile test, which is a claim also made after North Korea's 1998 satellite launch, and later rejected. The first (April 2012) launch of Kwangmyŏngsŏng-3 was unsuccessful, a fact publicly recognized by the DPRK. However, the December 2012 launch of the "second version" of Kwangmyŏngsŏng-3 was successful, putting the DPRK's first satellite into orbit.
- South Korea (Korea Aerospace Research Institute), after launching their first national satellite by foreign launcher in 1992, tried to launch a first KSLV own launcher (created with assistance of Russia) in 2009, 2011 and 2012, but all were unsuccessful.
[edit]Other notes
- ^ Russia and Ukraine were parts of the Soviet Union and thus inherited their launch capability without the need to develop it indigenously. Through Soviet Union they also are on the number one position in this list of accomplishments.
- France, United Kingdom, Ukraine launched their first satellites by own launchers from foreign spaceports.
- Some countries such as South Africa, Spain, Italy,[citation needed] Germany, Canada, Australia, Argentina,Egypt and private companies such as OTRAG, have developed their own launchers, but have not had a successful launch.
- Only eight countries from the list above (Russia and Ukraine instead of USSR, also USA, Japan, China, India, Israel and Iran) and one regional organization (the 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.)
- Several other countries, including South Korea, Brazil, Pakistan, Romania, Kazakhstan, Taiwan, Indonesia,Sri Lanka,[citation needed] Australia, New Zealand, Malaysia[citation needed] and Turkey, are at various stages of development of their own small-scale launcher capabilities.
[edit]Launch capable private entities
- Orbital Sciences Corporation is conducting launches using its Taurus I rocket.
- On September 28, 2008, the private aerospace firm SpaceX successfully launched its Falcon 1 rocket in to orbit. This marked the first time that a privately built liquid-fueled booster was able to reach orbit.[24] The rocket carried a prism shaped 1.5 m (5 ft) long payload mass simulator that was set into orbit. The dummy satellite, known as Ratsat, will remain in orbit for between five and ten years before burning up in the atmosphere.[24]
[edit]First satellites of countries
satellite operation, launched by foreign supplier
satellite in development
While Canada was the third country to build a satellite which was launched into space,
[31] 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.
[32] Australia's launch project (
WRESAT) involved a donated U.S. missile and U. S. support staff as well as a joint launch facility with the United Kingdom.
[33] The first satellite built by Singapore,
X-Sat, was launched aboard a
PSLVrocket on April 20, 2011.
[34]
Soviet Union
United States
France
Japan
China
United Kingdom
India
Israel
Russia[1]
Ukraine[1]
Iran
North Korea
South Korea
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