Satellites are used for many purposes

Launch capable private entities[edit]

Orbital Sciences Corporation 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[edit]

Main article: Timeline of first artificial satellites by country
  orbital launch and satellite operation
  satellite operation, launched by foreign supplier
  satellite in development
  orbital launch project at advanced stage or indigenous ballistic missiles deployed

While Canada was the third country to build a satellite which was launched into space,[32] 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.[33] The first Italian satellite San Marco 1 launched on 15 December 1964 on a U.S. Scout rocket from Wallops Island (Virginia, United States) with an Italian launch team trained by NASA.[34] By similar occasions, almost all further first national satellites was launched by foreign rockets.

Attempted first satellites[edit]

  • United States tried unsuccessfully to launch its first satellite in 1957; they were successful in 1958.
  • China tried unsuccessfully to launch its first satellite in 1969; they were successful in 1970.
  • Chile tried unsuccessfully in 1995 to launch its first satellite FASat-Alfa by foreign rocket; in 1998 they were successful.†
  • North Korea has tried in 1998, 2009, 2012 to launch satellites, first successful launch on 12 December 2012.[35]
  • Libya since 1996 developed its own national Libsat satellite project with the goal of providing telecommunication and remote sensing services[36] that was postponed after the fall of Gaddafi.
  • Belarus tried unsuccessfully in 2006 to launch its first satellite BelKA by foreign rocket.†

†-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[edit]

  • Armenia founded ArmCosmos in 2012[37] and announced an intention to create and launch the countries first telecommunication satellite, named ArmSat. The investment estimate is $250 million and potential contractors for building the satellite includes Russia, China and Canada.[38][39]
  • Cambodia's Royal Group plans to purchase for $250–350 million and launch in the beginning of 2013 the telecommunication satellite.[40]
  • Cayman Islands's Global IP Cayman private company plans to launch GiSAT-1 geostationary communications satellite in 2018.
  • Democratic Republic of Congo ordered at November 2012 in China (Academy of Space Technology (CAST) and Great Wall Industry Corporation (CGWIC)) the first telecommunication satellite CongoSat-1 which will be built on DFH-4 satellite bus platform and will be launched in China till the end of 2015.[41]
  • Croatia has a goal to construct a satellite by 2013–2014. Launch into Earth orbit would be done by a foreign provider.[42]
  • Ireland's team of Dublin Institute of Technology intends to launch the first Irish satellite within European University program CubeSat QB50.[43]
  • Republic of Moldova's first remote sensing satellite plans to start in 2013 by Space centre at national Technical University.[44]
  • Myanmar plans to purchase for $200 million their own telecommunication satellite.[45]
  • Nicaragua ordered for $254 million at November 2013 in China the first telecommunication satellite Nicasat-1 (to be built at DFH-4 satellite bus platform by CAST and CGWIC), that planning to launch in China at 2016.[46]
  • Paraguay under new Agencia Espacial del Paraguay –- AEP airspace agency plans first Eart observation satellite.[47][48]
  • Serbia's first satellite Tesla-1 was designed, developed and assembled by nongovernmental organisations in 2009 but still remains unlaunched.
  • Sri Lanka has a goal to construct two satellites beside of rent the national SupremeSAT payload in Chinese satellites. Sri Lankan Telecommunications Regulatory Commission has signed an agreement with Surrey Satellite Technology Ltd to get relevant help and resources. Launch into Earth orbit would be done by a foreign provider.[49][50]
  • Syrian Space Research Center developing CubeSat-like small first national satellite since 2008.[51]
  • Tunisia is developing its first satellite, ERPSat01. Consisting of a CubeSat of 1 kg mass, it will be developed by the Sfax School of Engineering. ERPSat satellite is planned to be launched into orbit in 2013.[52]
  • Uzbekistan's State Space Research Agency (UzbekCosmos) announced in 2001 about intention of launch in 2002 first remote sensing satellite.[53] Later in 2004 was stated that two satellites (remote sensing and telecommunication) will be built by Russia for $60–70 million each[54]
  • Bangladesh Bangladesh launched Bangabandhu-1 at 12 May 2018. SpaceX helped with the launching.

Attacks on satellites[edit]

Further information: Anti-satellite weapon

Since the mid-2000s, satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks.[55][56]

For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from earth. Russia, United States, China and India have demonstrated the ability to eliminate satellites.[57] In 2007 the Chinese military shot down an aging weather satellite,[57] followed by the US Navy shooting down a defunct spy satellite in February 2008.[58] On 27 March 2019 India shot down a live test satellite at 300 km altitude in 3 minutes. India became the fourth country to have the capability to destroy live satellites.[59][60]

Jamming[edit]

See also: Radio 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,[61][62] but satellite phone and television signals have also been subjected to jamming.[63][64]

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.[citation needed]

Earth observation[edit]

Main article: Earth observation satellite

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.[65]

The National Aeronautics and Space Administration (NASA)[66] 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.[67]

NASA[edit]

See also: Earth Observing System

The NASA introduced an Earth Observing System (EOS)[68] composed of several satellites, science component, and data system described as the Earth Observing System Data and Information System (EOSDIS). 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 (FTP) and Hyper Text Transfer Protocol Secure (HTTPS).[69] Scientists and researchers perform EOSDIS science operations within a distributed platform of multiple interconnected nodes or Science Investigator-led Processing Systems (SIPS) and discipline-specific Distributed Active Archive Centers (DACCs).[70]

ESA[edit]

The European Space Agency[71] have been operating Earth Observation satellites since the launch of Meteosat 1 in November 1977.[72] ESA currently has plans to launch a satellite equipped with an artificial intelligence (AI) processor that will allow the spacecraft to make decisions on images to capture and data to transmit to the Earth.[73] BrainSat will use the Intel Myriad X vision processing unit (VPU). The launching will be scheduled in 2019. ESA director for Earth Observation Programs Josef Aschbacher made the announcement during the PhiWeek in November 2018.[74] 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.[73] ESA also launched the PhiLab, referring to the future-focused team that works to harness the potentials of AI and other disruptive innovations.[75] 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.[76] Space Rider is the sequel of the Agency's Intermediate Experimental vehicle (IXV) which was launched in 2015. It has the capacity payload of 800 kilograms for orbital missions that will last a maximum of two months.[77]

Pollution and regulation[edit]

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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.[78] 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.[79][80] A report from the SATCON1 workshop in 2020 concluded that the effects of large satellite constellations can severely affect some astronomical research efforts and lists six ways to mitigate harm to astronomy.[81][82] Some notable satellite failures that polluted and dispersed radioactive materials are Kosmos 954, Kosmos 1402 and the Transit 5-BN-3. Using wood as an alternative material has been posited in order to reduce pollution and debris from satellites that reenter the atmosphere.[83]

Open source satellites[edit]

Several open source satellites both in terms of open source hardware and open source software were flown or are in development. The satellites have usually form of a CubeSat or PocketQube. In 2013 an amateur radio satellite OSSI-1 was launched and remained in orbit for about 2 months.[84] In 2017 UPSat created by the Greek University of Patras and Libre Space Foundation remained in orbit for 18 months. In 2019 FossaSat-1 was launched.[85][86][87][88] As of February 2021 the Portland State Aerospace Society is developing two open source satellites called OreSat[89][90] and the Libre Space Foundation also has ongoing satellite projects.[91][92][93]

Satellite services[edit]

See also[edit]

Subsystems[edit]

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.[16] Note that some novel architectural concepts such as Fractionated spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module[edit]

The bus module consists of the following subsystems:

Structure[edit]

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[edit]

The telemetry subsystem (aka Command and Data Handling, C&DH) 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[edit]

The power subsystem may consist 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 (Radioisotope thermoelectric generator) have also been used in several successful satellite programs including the Nimbus program (1964–1978).[21]

Thermal control[edit]

Main article: Spacecraft thermal control

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)

Attitude and orbit control[edit]

Main articles: Attitude control and Spacecraft propulsion

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

Communications[edit]

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).

End of life[edit]

When satellites reach the end of their mission (this normally occurs within 3 or 4 years after launch), 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 March 2015, as well as the upper stage of its launch rocket.[22][23]

Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit.[24] 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.[25] 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 (as well as those exercised by large mountain ranges, whether above or below sea level). 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.[26]

Launch-capable countries[edit]

Main article: Timeline of first orbital launches by country

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.

 

 n 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, about 5,000 remained in orbit. Of those, about 1,900 were operational, while the rest had exceeded their useful lives and become space debris. Approximately 63% of operational satellites are in low Earth orbit, 6% are in medium-Earth orbit (at 20,000 km), 29% are in geostationary orbit (at 36,000 km) and the remaining 2% are in various elliptical orbits. In terms of countries with the most satellites, the United States has the most with 1,897 satellites, China is second with 412, and Russia third with 176.[1] A few large space stations, including the International Space Station, 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,[2] 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 (overlapping) 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 (see air launch to orbit).

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.

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