Satellite


In the context of spaceflight, a satellite is an object that has been intentionally placed into orbit. These objects are called artificial satellites to distinguish them from natural satellites such as Earth's Moon.
On 4 October 1957 the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since then, about 8,900 satellites from more than 40 countries have been launched. According to a 2018 estimate, some 5,000 remain in orbit. Of those about 1,900 were operational, while the rest have lived out their useful lives and become space debris. Approximately 63% of operational satellites are in low Earth orbit, 6% are in medium-Earth orbit, 29% are in geostationary orbit and the remaining 2% are in elliptic orbit. In terms of countries with the most satellites the USA significantly leads the way with 859 satellites, China is second with 250, and Russia third with 146. These are then followed by Japan, India and the UK.
A few large space stations have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites of the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, a comet and the Sun.
Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of planetary surfaces, and also take pictures of planets they are launched into. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and space telescopes. Space stations and human spacecraft in orbit are also satellites.
Satellites can operate by themselves or as part of a larger system, a satellite formation or satellite constellation.
Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known classes include low Earth orbit, polar orbit, and geostationary orbit.
A launch vehicle is a rocket that places a satellite into orbit. Usually, it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, or aboard a plane.
Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, scientific instrumentation, communication, etc.

History

The first published mathematical study of the possibility of an artificial satellite was Newton's cannonball, a thought experiment in A Treatise of the System of the World by Isaac Newton. The first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon. The idea surfaced again in Jules Verne's The Begum's Fortune.
In 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion 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, and that a multi-stage rocket fueled by liquid propellants could achieve this.
In 1928, Herman Potočnik published his sole book, The Problem of Space Travel – The Rocket Motor. He described the use of orbiting spacecraft for observation of the ground and described how the special conditions of space could be useful for scientific experiments.
In a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet.
In May 1946, the United States Air Force's Project RAND released the Preliminary Design of an Experimental World-Circling Spaceship, which stated that "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. Project RAND eventually released the report, but considered the satellite to be a tool for science, politics, and propaganda, rather than a potential military weapon. In February 1954 Project RAND released "Scientific Uses for a Satellite Vehicle," written by R.R. Carhart. This expanded on potential scientific uses for satellite vehicles and was followed in June 1955 with "The Scientific Use of an Artificial Satellite," by H.K. Kallmann and W.W. Kellogg.
In the context of activities planned for the International Geophysical Year, the White House announced on 29 July 1955 that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On 31 July, the Soviets announced that they intended to launch a satellite by the fall of 1957.
The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957 under the Sputnik program, with Sergei Korolev as chief designer. 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. 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.
Sputnik 2 was launched on 3 November 1957 and carried the first living passenger into orbit, a dog named Laika.
In early 1955, following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, the Army and Navy were working on Project Orbiter with two competing programs. The army used the Jupiter C rocket, while the civilian/Navy program used the Vanguard rocket to launch a satellite. Explorer 1 became the United States' first artificial satellite on 31 January 1958.
In June 1961, three-and-a-half years after the launch of Sputnik 1, the United States Space Surveillance Network cataloged 115 Earth-orbiting satellites.
Early satellites were constructed to unique designs. With advancements in technology, multiple satellites began to be built on single model platforms called satellite buses. The first standardized satellite bus design was the HS-333 geosynchronous communication satellite launched in 1972.
Currently the largest artificial satellite ever is the International Space Station.

Tracking

Satellites can be tracked from Earth stations and also from other satellites.

Space Surveillance Network

The United States Space Surveillance Network, a division of the United States Strategic Command, has been tracking objects in Earth's orbit since 1957 when the Soviet Union 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-artificial 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, the rest are space debris. 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.

Services

There are three basic categories of 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.

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.

Scientific research satellites (commercial and noncommercial)

Scientific research satellites provide meteorological information, land survey data, Amateur Radio, and other different scientific research applications such as earth science, marine science, and atmospheric research.

Types

The first satellite, Sputnik 1, was put into orbit around Earth and was therefore in geocentric orbit. This is the most common type of orbit by far, with approximately 1,886 artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and eccentricity.
The commonly used altitude classifications of geocentric orbit are Low Earth orbit, Medium Earth orbit and High Earth orbit. Low Earth orbit is any orbit below 2,000 km. Medium Earth orbit is any orbit between 2,000 and 35,786 km. High Earth orbit is any orbit higher than 35,786 km.

Centric classifications

Inclination classifications

The satellite's functional versatility is embedded within its technical components and its operations characteristics. Looking at the "anatomy" of a typical satellite, one discovers two modules. Note that some novel architectural concepts such as Fractionated spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module

The bus module consists of the following subsystems:

Structural subsystem

The structural subsystem provides the mechanical base structure with adequate stiffness to withstand stress and vibrations experienced during launch, maintain structural integrity and stability while on station in orbit, and shields the satellite from extreme temperature changes and micro-meteorite damage.

Telemetry subsystem

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.

Power subsystem

The power subsystem consists of solar panels to convert solar energy into electrical power, regulation and distribution functions, and batteries that store power and supply the satellite when it passes into the Earth's shadow. Nuclear power sources have also been used in several successful satellite programs including the Nimbus program.

Thermal control subsystem

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

Attitude and orbit control subsystem

The attitude and orbit control subsystem consists of sensors to measure vehicle orientation, control laws embedded in the flight software, and actuators. These apply the torques and forces needed to re-orient the vehicle to a desired attitude, keep the satellite in the correct orbital position, and keep antennas pointed in the right directions.

Communication payload

The second major module is the communication payload, which is made up of transponders. A transponder is capable of :
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 artificial satellite to be put in Geocentric orbit, was still in orbit as of 2015, as well as the upper stage of its launch rocket.
Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit. As of 2002, the FCC requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch. In cases of uncontrolled de-orbiting, the major variable is the solar flux, and the minor variables the components and form factors of the satellite itself, and the gravitational perturbations generated by the Sun and the Moon. The nominal breakup altitude due to aerodynamic forces and temperatures is 78 km, with a range between 72 and 84 km. Solar panels, however, are destroyed before any other component at altitudes between 90 and 95 km.

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. The list does not include the European Space Agency, a multi-national state organization, nor private consortiums.


OrderCountryDate of first launchRocketSatellite
1Soviet Union4 October 1957Sputnik-PSSputnik 1
2United States1 February 1958Juno IExplorer 1
3France26 November 1965Diamant-AAstérix
4Japan11 February 1970Lambda-4SOhsumi
5China24 April 1970Long March 1Dong Fang Hong I
6United Kingdom28 October 1971Black ArrowProspero
7India18 July 1980SLVRohini D1
8Israel19 September 1988ShavitOfeq 1
Russia21 January 1992Soyuz-UKosmos 2175
Ukraine13 July 1992Tsyklon-3Strela
9Iran2 February 2009Safir-1Omid
10North Korea12 December 2012Unha-3Kwangmyŏngsŏng-3 Unit 2
11South Korea30 January 2013Naro-1STSAT-2C
12New Zealand12 November 2018ElectronCubeSat

Attempted first launches

launched a satellite into orbit on the Pegasus in 1990. SpaceX launched a satellite into orbit on the Falcon 1 in 2008. Rocket Lab launched three cubesats into orbit on the Electron in 2018.

First satellites of countries

CountryYear of first launchFirst satelliteOperational payloads
in orbit as of April 2020
Soviet Union
1957
Sputnik 1
1524
United States1958Explorer 11914
China1970Dong Fang Hong I0391
Japan1970Ohsumi0181
India1975Aryabhata0096
France1965Astérix0073
Germany1969Azur0067
Canada1962Alouette 10054
United Kingdom1962Ariel 10054
Italy1964San Marco 10029
South Korea1992Kitsat A23
Spain1974Intasat00027
Australia1967WRESAT0022
Brazil1985Brasilsat-A10021
Argentina1990Lusat20
Israel1988Ofeq 100020
Indonesia1976Palapa A118
Turkey1994Turksat 1B13
Saudi Arabia1985Arabsat-1A0015
Mexico1985Morelos 113
Sweden1986Viking0011
Singapore1998ST-111
Netherlands1974ANS0008
Czechoslovakia1978Magion 12
Bulgaria1981Intercosmos Bulgaria 13000002
Luxembourg1988Astra 1A4
Pakistan1990Badr-16
Portugal1993PoSAT-12
Thailand1993Thaicom 110
Czech Republic1995Magion 43
Ukraine1995Sich-10006
Malaysia1996MEASAT7
Norway1997Thor 29
Philippines1997Mabuhay 10002
Egypt1998Nilesat 1015
Chile1998FASat-Bravo3
Denmark1999Ørsted9
South Africa1999SUNSAT6
United Arab Emirates2000Thuraya 19
Morocco2001Maroc-Tubsat0001
Belgium2001PROBA-10
Tonga2002Esiafi 1 0
Algeria2002Alsat 16
Greece2003Hellas Sat 24
Cyprus2003Hellas Sat 20
Nigeria2003Nigeriasat 16
Iran2005Sina-10001
Kazakhstan2006KazSat 16
Colombia2007Libertad 10
Mauritius2007Rascom-QAF 10
Vietnam2008Vinasat-10003
Venezuela2008Venesat-13
Switzerland2009SwissCube-10
Isle of Man2011ViaSat-10001
Poland2012PW-Sat00004
Hungary2012MaSat-10000
Sri Lanka2012SupremeSAT-I1
Romania2012Goliat0
Belarus2012BKA 2
North Korea2012Kwangmyŏngsŏng-3 Unit 22
Azerbaijan2013Azerspace1
Austria2013TUGSAT-1/UniBRITE0
Bermuda2013Bermudasat 1 0
Ecuador2013NEE-01 Pegaso2
Estonia2013ESTCube-11
Jersey2013O3b-1, −2, −3, −40
Qatar2013Es'hailSat10
Peru2013PUCPSAT-12
Bolivia2013TKSat-11
Lithuania2014LituanicaSAT-1 and LitSat-11
Uruguay2014Antelsat1
Iraq2014Tigrisat0
Turkmenistan2015TurkmenAlem52E/MonacoSAT1
Laos2015Laosat-11
Finland2017Aalto-21
Bangladesh2017BRAC Onnesha2
Ghana2017GhanaSat-11
Mongolia2017Mazaalai1
Latvia2017Venta-11
Slovakia2017skCUBE1
Asgardia2017Asgardia-11
Angola2017AngoSat 11
New Zealand2018Humanity Star1
Bangladesh2018Bangabandhu-11
Costa Rica2018Proyecto Irazú1
Kenya20181KUNS-PF1
Bhutan2018BHUTAN-11
Jordan2018JY1-SAT1
Nepal2019NepaliSat-11
Rwanda2019RWASat-11
Sudan2019SRSS-11
Ethiopia2019ETRSS-11
Guatemala2020Quetzal-11

While Canada was the third country to build a satellite which was launched into space, it was launched aboard an American rocket from an American spaceport. The same goes for Australia, who launched first satellite involved a donated U.S. Redstone rocket and American support staff as well as a joint launch facility with the United Kingdom. The first Italian satellite San Marco 1 launched on 15 December 1964 on a U.S. Scout rocket from Wallops Island with an Italian launch team trained by NASA. By similar occasions, almost all further first national satellites was launched by foreign rockets.

Attempted first satellites

†-note: Both Chile and Belarus used Russian companies as principal contractors to build their satellites, they used Russian-Ukrainian manufactured rockets and launched either from Russia or Kazakhstan.

Planned first satellites

Since the mid-2000s, satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks.
For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from earth. Russia, the United States, China and India have demonstrated the ability to eliminate satellites. In 2007 the Chinese military shot down an aging weather satellite, followed by the US Navy shooting down a defunct spy satellite in February 2008. On 27 March 2019 India shot down a live test satellite at 300 km altitude in 3 minutes. India became the fourth country to having capability to destroy live satellite.

Jamming

Due to the low received signal strength of satellite transmissions, they are prone to jamming by land-based transmitters. Such jamming is limited to the geographical area within the transmitter's range. GPS satellites are potential targets for jamming, but satellite phone and television signals have also been subjected to jamming.
Also, it is very easy to transmit a carrier radio signal to a geostationary satellite and thus interfere with the legitimate uses of the satellite's transponder. It is common for Earth stations to transmit at the wrong time or on the wrong frequency in commercial satellite space, and dual-illuminate the transponder, rendering the frequency unusable. Satellite operators now have sophisticated monitoring that enables them to pinpoint the source of any carrier and manage the transponder space effectively.

Earth observation

During the last five decades, space agencies have sent thousands of space crafts, space capsules, or satellites to the universe. In fact, weather forecasters make predictions on the weather and natural calamities based on observations from these satellites.
The National Aeronautics and Space Administration requested the National Academies to publish a report entitled, Earth Observations from Space; The First 50 Years of Scientific Achievements in 2008. It described how the capability to view the whole globe simultaneously from satellite observations revolutionized studies about the planet Earth. This development brought about a new age of combined Earth sciences. The National Academies report concluded that continuing Earth observations from the galaxy are necessary to resolve scientific and social challenges in the future.

NASA

The NASA introduced an Earth Observing System composed of several satellites, science component, and data system described as the Earth Observing System Data and Information System. It disseminates numerous science data products as well as services designed for interdisciplinary education. EOSDIS data can be accessed online and accessed through File Transfer Protocol and Hyper Text Transfer Protocol Secure. Scientists and researchers perform EOSDIS science operations within a distributed platform of multiple interconnected nodes or Science Investigator-led Processing Systems and discipline-specific Distributed Active Archive Centers.

ESA

The European Space Agency have been operating Earth Observation satellites since the launch of Meteosat 1 in November 1977. ESA currently has plans to launch a satellite equipped with an artificial intelligence processor that will allow the spacecraft to make decisions on images to capture and data to transmit to the Earth. BrainSat will use the Intel Myriad X vision processing unit. The launching will be scheduled in 2019. ESA director for Earth Observation Programs Josef Aschbacher made the announcement during the PhiWeek in November 2018. This is the five-day meet that focused on the future of Earth observation. The conference was held at the ESA Center for Earth Observation in Frascati, Italy. ESA also launched the PhiLab, referring to the future-focused team that works to harness the potentials of AI and other disruptive innovations. Meanwhile, the ESA also announced that it expects to commence the qualification flight of the Space Rider space plane in 2021. This will come after several demonstration missions. Space Rider is the sequel of the Agency's Intermediate Experimental vehicle which was launched in 2015. It has the capacity payload of 800 kilograms for orbital missions that will last a maximum of two months.

SpaceX

SpaceX was scheduled to launch a multiple satellite mission on 28 November 2018 from the United States Vandenberg Air Force Base after an initial 19 November schedule. The launch is expected to be visible once the rocket heads toward the south into an Earth observation trajectory traveling over the poles. However, the second supposed launched was delayed again because of poor weather conditions and the actual launch occurred on 3 December 2018. The mission is known as the SSO-A Smallsat Express was executed by Spaceflight, a rideshare and mission management provider based in Seattle, Wash. The launch was a landmark for Elon Musk, founder of SpaceX which had 19 rocket launches in 2018 alone. The estimated cost of this Falcon 9 rocket is approximately $62 million. The rocket has 60 satellites with each one going separate ways. On April 22, 2020, SpaceX launched their 7th constellation of 60 satellites, boosting the StarLink constellation to a total of 420 satellites in low Earth orbit.

Amazon and Lockheed

Amazon Web Services and Lockheed Martin entered into a strategic partnership for the purpose of integrating the AWS ground station service with Lockheed's verge antenna network. These two corporations aim to merge these highly-capable systems that will provide clients with robust satellite uplinks and downlinks. Through these systems, users can incorporate satellite data with various AWS services which include computing, storage, analytics, and machine-learning.

Pollution and regulation

Generally liability has been covered by the Liability Convention.
Issues like space debris, radio and light pollution are increasing in magnitude and at the same time lack progress in national or international regulation.
With future increase in numbers of satellite constellations, like SpaceX Starlink, it is feared especially by the astronomical community, such as the IAU, that orbital pollution will increase significantly. Some notable satellite failures that polluted and dispersed radioactive materials are Kosmos 954, Kosmos 1402 and the Transit 5-BN-3.

Satellite services