What is the fundamental definition of an artificial satellite?

An artificial satellite is an object, typically a spacecraft, that has been intentionally placed into orbit around a celestial body. This distinguishes them from natural satellites, such as moons.

What are the diverse applications of artificial satellites?

Artificial satellites serve a wide array of purposes, including communication relay, weather forecasting, navigation (like GPS), broadcasting, scientific research, and Earth observation. They also have military applications such as reconnaissance, early warning systems, signals intelligence, and potentially weapon delivery.

What are the typical power generation systems found on most satellites?

Most satellites are equipped with an electricity generation system to power their onboard equipment. Common sources include solar panels, which convert sunlight into electricity, and radioisotope thermoelectric generators (RTGs) for missions in deep space where sunlight is limited.

How do satellites communicate with Earth, and what component facilitates this?

Satellites communicate with ground stations using components called transponders. These transponders relay and amplify radio telecommunication signals, creating a communication channel between the satellite and Earth.

Why are standardized satellite buses, like CubeSats, popular?

Many satellites utilize a standardized platform, known as a satellite bus, to reduce costs and development time. CubeSats are a particularly popular example of these standardized designs, often used for smaller satellite missions.

What design consideration is crucial for satellites due to the high cost of space launch?

Because the cost of launching objects into space is very high, satellites are generally designed to be as lightweight and robust as possible. This minimizes launch expenses while ensuring the satellite can withstand the harsh conditions of space.

How do satellites achieve and maintain their orbits?

Spaceships become satellites by reaching orbital velocities, which means accelerating or decelerating to maintain a stable path around a celestial body. They can adjust or maintain their orbits using propulsion systems, typically chemical or ion thrusters, and must be positioned high enough to avoid atmospheric drag and stay above their Roche limit.

What are the most common orbital destinations for satellites orbiting Earth?

As of 2018, the majority of satellites orbiting Earth were found in either low Earth orbit (LEO) or geostationary orbit (GEO). Geostationary orbit is notable because satellites in this orbit appear stationary relative to a fixed point on the ground.

What is a Sun-synchronous orbit, and why is it used?

A Sun-synchronous orbit is a specific type of orbit chosen by some imaging satellites. This orbit allows the satellite to pass over any given point on Earth's surface at the same local solar time, ensuring consistent lighting conditions for Earth observation.

What is the primary concern regarding the increasing number of satellites and space debris?

The growing number of satellites and the associated space debris pose an increasing threat of collisions. This escalating problem could potentially make certain regions of space unusable for future space activities.

What is an orbiter in the context of spaceflight?

An orbiter is a type of spacecraft specifically designed to enter orbit around an astronomical body. Upon successfully achieving orbit, it becomes an artificial satellite of that body.

What kind of information do Earth observation satellites gather?

Earth observation satellites gather data for various purposes, including reconnaissance, mapping, and monitoring the weather, oceans, and forests. They provide valuable information for scientific research and environmental management.

How do space telescopes leverage the conditions of outer space?

Space telescopes take advantage of the near-perfect vacuum of outer space to observe celestial objects across the entire electromagnetic spectrum. This environment minimizes atmospheric interference that would affect ground-based telescopes.

What is the significance of signal delay and predictability for satellite navigation systems?

Satellite navigation systems, such as GPS, utilize the predictable timing of signals transmitted by satellites. The known delay of these radio waves allows receivers on the ground to calculate their precise location in real-time.

What were the first artificial satellites launched into Earth's orbit?

The first artificial satellite launched into Earth's orbit was Sputnik 1, by the Soviet Union on October 4, 1957. The United States' first satellite was Explorer 1, launched on January 31, 1958.

What historical event did the launch of Sputnik 1 precipitate in the United States?

The launch of Sputnik 1 by the Soviet Union caused the Sputnik crisis in the United States. This event heightened Cold War tensions and spurred the American space program, igniting the Space Race.

What significant discovery was made thanks to data from the United States' first satellite, Explorer 1?

Explorer 1, launched in 1958, carried a radiation detector whose data led to the discovery of the Earth's Van Allen radiation belts. These belts are regions of energetic charged particles trapped by the Earth's magnetic field.

What was the purpose of the TIROS-1 spacecraft?

TIROS-1, launched in 1960, was part of NASA's Television Infrared Observation Satellite program. It was notable for transmitting the first television footage of weather patterns captured from space.

How did the development of standardized satellite buses change satellite manufacturing?

Initially, satellites were built with unique designs. However, with technological advancements, multiple satellites began to be constructed on standardized platforms called satellite buses, improving efficiency and reducing costs. The HS-333 geosynchronous communication satellite, launched in 1972, was an early example of a standardized bus design.

What is the International Space Station's status in terms of satellite size?

The International Space Station (ISS) holds the distinction of being the largest artificial satellite ever constructed. It serves as a habitable artificial satellite in low Earth orbit, functioning as a research laboratory.

What trend emerged in satellite design in the early 2000s, particularly with CubeSats and microsatellites?

Following the rise of CubeSats and microsatellites, particularly those launched into low Earth orbit (LEO), satellites began to be more frequently designed for complete destruction or burn-up upon atmospheric reentry at the end of their operational life. This is a measure to mitigate space debris.

What are the primary methods satellites use for orbit and altitude control?

Satellites primarily use chemical or ion propulsion systems to adjust or maintain their orbits. Additionally, reaction wheels are employed to control the satellite's attitude, or orientation, in three-axis rotation.

What external factors can affect satellites, especially those closer to Earth?

Satellites, particularly those in lower orbits, are influenced by variations in Earth's magnetic and gravitational fields, as well as solar radiation pressure. Satellites farther from Earth are more affected by the gravitational pull of the Moon and the Sun.

What are the common types of propellants used in satellite thrusters?

Chemical thrusters on satellites commonly use monopropellants (like hydrazine) or bipropellants (like monomethylhydrazine and dinitrogen tetroxide). Ion thrusters, often Hall-effect thrusters, typically use xenon gas due to its inert nature and ease of ionization.

What is the main difference in efficiency and thrust between ion and chemical propulsion?

Ion propulsion is generally more efficient in terms of propellant usage compared to chemical propulsion. However, ion thrusters produce very small amounts of thrust, requiring longer operational periods to achieve orbital changes.

Besides solar panels, what other power source is used for satellites in deep space?

For satellites operating in deep space, where sunlight is minimal, radioisotope thermoelectric generators (RTGs) are often used as a power source. These devices convert heat generated from the decay of radioactive material into electricity.

Why do satellites with solar panels also need batteries?

Satellites equipped with solar panels require batteries to store energy. This is essential because solar panels cannot generate power when the satellite is passing through Earth's shadow (at night) or when enclosed within a launch vehicle during ascent.

What types of batteries are commonly used in satellites?

The most common types of batteries used in modern satellites are lithium-ion batteries. Historically, nickel-hydrogen batteries were also widely employed.

What is remote sensing in the context of Earth observation satellites?

Remote sensing refers to the practice of gathering information about Earth's surface and atmosphere from a distance, typically using satellites equipped with various sensors. This data is used for applications like mapping, environmental monitoring, and weather forecasting.

What instruments might an Earth observation satellite carry?

Depending on their specific functions, Earth observation satellites can be equipped with a range of instruments, including normal cameras, radar systems, lidar, photometers, and specialized atmospheric sensors.

How do weather satellites contribute to environmental monitoring?

Weather satellites monitor various atmospheric and surface phenomena, including clouds, fires, pollution effects, auroras, dust storms, snow cover, and ice fields. They also track ocean currents and energy flows, providing crucial data for climate studies and disaster management.

How can environmental monitoring satellites detect changes in vegetation?

By analyzing data over time, environmental monitoring satellites can detect changes in Earth's vegetation cover and atmospheric composition. This allows for the monitoring of droughts by comparing current vegetation health to long-term averages.

What is the primary function of a communications satellite?

A communications satellite acts as a relay station in orbit, receiving, amplifying, and retransmitting radio and microwave signals. This enables telecommunications services like television, telephone, and internet across vast geographical distances.

What is the advantage of geostationary orbit for some communication satellites?

Communication satellites in geostationary orbit (GEO) are positioned approximately 22,236 miles above the equator, maintaining a fixed position relative to the Earth's surface. This allows ground-based antennas to be permanently aimed at the satellite without needing to track its movement.

What is the purpose of frequency allocation for satellite communications?

International organizations regulate the use of radio and microwave frequency bands for satellite communications to prevent signal interference. This careful allocation ensures that different services can operate without disrupting each other.

When is an Earth observation or communication satellite referred to as a spy satellite?

An Earth observation or communication satellite is classified as a spy satellite, or reconnaissance satellite, when it is deployed for military or intelligence purposes. Its functions can include early missile warning, nuclear explosion detection, and surveillance through optical or radar imaging.

How do navigational satellites enable location determination?

Navigational satellites transmit precise radio time signals. Mobile receivers on the ground can interpret these signals, along with the satellite's position, to calculate their exact location with high accuracy in real-time.

What are astronomical satellites used for?

Astronomical satellites, also known as space telescopes, are designed to observe distant objects in space, such as planets, galaxies, and other celestial phenomena. They operate above Earth's atmosphere, providing clearer observations across the electromagnetic spectrum.

What are tether satellites?

Tether satellites are a type of experimental satellite connected to another satellite by a long, thin cable known as a tether. This configuration allows for unique experiments related to orbital dynamics and energy generation.

What is the purpose of recovery satellites?

Recovery satellites are designed to retrieve payloads, such as scientific experiments or manufactured materials, from orbit and return them safely to Earth. This capability is crucial for scientific research and space-based manufacturing.

What are biosatellites designed to do?

Biosatellites are specifically engineered to carry living organisms into space. They are primarily used for scientific experiments to study the effects of spaceflight on biological systems.

What are space-based solar power satellites?

Space-based solar power satellites are a proposed concept for satellites designed to collect solar energy in space and transmit it wirelessly to Earth or other locations. This technology aims to provide a clean and continuous energy source.

What military capabilities have been demonstrated by certain nations regarding satellites?

Several nations, including Russia, the United States, China, and India, have demonstrated the capability to destroy satellites in orbit using anti-satellite (ASAT) missiles. These tests are often conducted for military testing and strategic deterrence purposes.

What environmental concerns are associated with rocket launches?

Rocket launches release various pollutants into different atmospheric layers, including black carbon, CO2, nitrogen oxides, and aluminum. These emissions, particularly in the stratosphere, can potentially impact the ozone layer and contribute to atmospheric warming.

How can rocket emissions contribute to ozone depletion?

Certain chemical compounds released by rockets, such as nitrogen oxides (NOx), can act as catalysts in the stratosphere to deplete the ozone layer through complex chemical reactions. While current launch rates have a minor impact, significant increases could exacerbate this issue.

What environmental impact do LEO satellites have during their operational lifetime?

Low Earth Orbit (LEO) satellites can impact the upper atmosphere through orbital decay, which requires repositioning using thrusters. The propellant, often hydrazine, releases gases like ammonia, hydrogen, and nitrogen. Additionally, atomic oxygen in the upper atmosphere can degrade satellite materials, releasing gases like CO2 and CO.

How might the increasing number of satellites affect the night sky?

The proliferation of satellites, especially large constellations, can increase the diffuse brightness of the night sky. This artificial light pollution may potentially disorient nocturnal organisms that rely on celestial patterns for navigation and orientation.

What is the concern regarding uncontrolled satellite de-orbiting?

Uncontrolled de-orbiting of satellites can pose environmental risks, particularly if they contain radioactive materials, as seen in cases like Kosmos 954. When satellites burn up during reentry, they also introduce materials and pollutants into the atmosphere.

What is the purpose of moving defunct satellites to a graveyard orbit?

To mitigate the problem of space debris, defunct satellites are sometimes moved to a 'graveyard orbit,' which is a higher orbit further from Earth. However, this is a temporary solution as these satellites remain in space for centuries.

What is the Kessler Syndrome, and how does space debris relate to it?

The Kessler Syndrome is a hypothetical scenario where the density of objects in low Earth orbit becomes so high that collisions between objects generate a cascade of debris, rendering space unusable. The increasing amount of space debris poses a significant risk of triggering this phenomenon.

Satellite Wiki: Orbital Sentinels: Understanding the World of Artificial Satellites

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Defining the Artificial Satellite

Celestial Objects in Orbit

An artificial satellite, commonly referred to as a satellite, is a human-made object intentionally placed into orbit around a celestial body. These sophisticated machines serve a multitude of critical functions, ranging from communication relay and weather forecasting to advanced scientific research and global navigation systems like GPS.

Diverse Utility

Beyond their civilian applications, satellites are integral to military operations, providing reconnaissance, early warning systems, signals intelligence, and potentially weapon delivery capabilities. The spectrum of satellite use underscores their profound impact on modern society, technology, and global security.

Reaching Orbit

Spaceships achieve satellite status by reaching specific orbital velocities, either through acceleration or deceleration. This ensures they maintain a stable trajectory, avoiding orbital decay caused by atmospheric drag, and remain within a designated orbit above the celestial body's Roche limit. Launch systems are the primary means by which these spacecraft are propelled into space.

Historical Trajectory

Early Conceptualizations

The theoretical foundation for artificial satellites was laid by Isaac Newton's "cannonball" thought experiment in 1687, illustrating orbital mechanics. Fictional depictions emerged in the late 19th century, with Edward Everett Hale's "The Brick Moon" in 1869. Konstantin Tsiolkovsky's seminal 1903 work, "Exploring Space Using Jet Propulsion Devices," provided the first academic analysis of rocketry for space travel, calculating necessary orbital speeds and proposing multi-stage rockets.

1687: Isaac Newton's "cannonball" thought experiment outlines principles of orbital motion.
1869: Edward Everett Hale publishes "The Brick Moon," a fictional account of an orbiting satellite.
1903: Konstantin Tsiolkovsky publishes "Exploring Space Using Jet Propulsion Devices," detailing rocket propulsion for spaceflight.
1928: Herman Potočnik's book "The Problem of Space Travel" discusses geostationary satellites and their potential uses.
1945: Arthur C. Clarke's article in "Wireless World" details the concept of geostationary communications satellites.
1946: The U.S. Air Force's Project RAND releases "Preliminary Design of an Experimental World-Circling Spaceship," highlighting scientific and strategic potential.

The Dawn of the Space Age

The launch of Sputnik 1 by the Soviet Union on October 4, 1957, marked the beginning of the space age and the era of artificial satellites. This event spurred the "Sputnik crisis" in the United States and ignited the Space Race. The U.S. responded with Project Vanguard and successfully launched its first satellite, Explorer 1, on January 31, 1958, which led to the discovery of the Van Allen radiation belts.

October 4, 1957: Sputnik 1 (Soviet Union) - First artificial satellite.
November 3, 1957: Sputnik 2 (Soviet Union) - Carried the dog Laika, the first living passenger into orbit.
January 31, 1958: Explorer 1 (United States) - First U.S. satellite, discovered Van Allen belts.
April 1, 1960: TIROS-1 (United States) - First television images of weather patterns from space.
November 26, 1965: Astérix (France) - France became the sixth nation to launch its own satellite.

Technological Evolution

Early satellites were custom-built, but technological advancements led to standardized satellite bus platforms, improving cost-effectiveness and efficiency. The late 2010s saw a significant increase in satellite launches, particularly with large internet constellations, prompting discussions on satellite lifespan management and planned deorbiting. The International Space Station remains the largest artificial satellite ever constructed.

1972: HS-333, the first standardized geosynchronous communication satellite bus.
Late 2010s: Rise of large satellite internet constellations (e.g., Starlink) dramatically increasing the number of satellites.
Present: Focus on demisable satellites and planned deorbiting to mitigate space debris.
Ongoing: Development of novel materials like wood for satellite construction (e.g., Japan's LingoSat).

Core Components and Systems

Orbit and Attitude Control

Maintaining a satellite's position and orientation is crucial for its functionality. This is achieved through sophisticated systems:

Propulsion Systems: Chemical thrusters (monopropellant or bipropellant, often hypergolic like hydrazine) and ion thrusters are used for orbital adjustments and station-keeping. Ion thrusters, while less thrusting, are more propellant-efficient.
Attitude Control: Reaction wheels and thrusters are employed to control the satellite's three-axis rotation and orientation, ensuring communication antennas and instruments are properly aimed.
Environmental Factors: Satellites must contend with Earth's magnetic and gravitational fields, solar radiation pressure, and the gravitational influence of other celestial bodies, necessitating continuous control.

Power Generation and Storage

Satellites require a reliable power source to operate their onboard equipment. The primary methods include:

Solar Panels: The most common method, converting sunlight into electricity. Panels often rotate via slip rings to maximize solar exposure.
Radioisotope Thermoelectric Generators (RTGs): Used for deep-space missions where sunlight is insufficient.
Batteries: Essential for storing power, especially during eclipses (when sunlight is blocked) or when the satellite is within the launch vehicle. Lithium-ion and nickel-hydrogen batteries are common types.

Diverse Applications

Earth Observation

Satellites designed for Earth observation, often placed in Low Earth Orbit (LEO) for high resolution or geostationary orbit (GEO) for continuous coverage, gather vital data through various instruments like cameras, radar, lidar, and atmospheric sensors. This data supports fields such as archaeology, cartography, environmental monitoring, meteorology, and reconnaissance.

Weather Monitoring: Tracking clouds, storms, and atmospheric conditions.
Environmental Monitoring: Assessing vegetation health, pollution levels, ice mapping, and ocean currents.
Mapping and Reconnaissance: Creating detailed maps and providing surveillance capabilities.
Climate Studies: Collecting data on Earth's radiation budget and climate change indicators.

Communication

Communications satellites act as crucial relay stations, amplifying and transmitting radio and microwave signals globally. They enable television broadcasting, telephony, internet access, and military communications. While GEO satellites offer fixed-point coverage, LEO constellations require ground antennas to track and switch between satellites.

Signal Relay: Overcoming Earth's curvature for long-distance communication.
Frequency Allocation: International regulations manage frequency bands to prevent interference.
GEO vs. LEO: Geostationary orbits provide constant coverage, while Low Earth Orbit constellations offer global coverage with frequent handoffs.

Navigation

Navigational satellites transmit precise radio time signals, enabling ground-based receivers to determine their exact location. Systems like GPS rely on these signals, achieving high accuracy through real-time calculations. The clear line of sight between satellites and receivers is fundamental to their operation.

Scientific Observation

Space telescopes, such as the Hubble and James Webb Space Telescopes, leverage the vacuum of space to observe celestial objects across the electromagnetic spectrum without atmospheric interference. Other satellites conduct astronomical research, study planetary bodies, and perform various scientific experiments.

Military and Experimental

Satellites are vital for military intelligence, reconnaissance, and early warning systems. They can also serve experimental purposes, such as tether satellites connected by cables or biosatellites carrying living organisms for research. Proposed space-based solar power satellites aim to collect and transmit energy.

Environmental Considerations

Resource Use and Manufacturing

The production of satellites and their launch vehicles involves significant resource consumption. Materials like aluminum, lithium, gold, and gallium are critical, with their extraction and processing carrying substantial environmental impacts. Booster stages are often discarded into the ocean, representing a considerable material footprint.

Aluminum: Constitutes ~40% of a satellite's mass; its production is carbon-intensive.
Rare Elements: Lithium, gold, and gallium are vital but have mining-related environmental consequences.
Launch Vehicles: Booster stages, often made of steel, are typically not recovered, contributing to oceanic material deposition.

Launch Emissions

Rocket launches release pollutants into various atmospheric layers. While greenhouse gas emissions are relatively small compared to aviation, byproducts like black carbon, nitrogen oxides, and water vapor can persist in the stratosphere, potentially affecting the ozone layer and contributing to atmospheric warming. The impact is still under active study.

Stratospheric Impact: Pollutants released above the tropopause can remain for extended periods.
Ozone Depletion: Radicals like NO_x, HO_x, and ClO_x can deplete ozone.
Climate Effects: Black carbon absorption of solar radiation can cause stratospheric warming and alter circulation patterns.
Water Vapor: Contributes to HO_x formation and ice particle creation, potentially aiding ozone loss.

Operational and Deorbit Impacts

During their operational life, satellites can release gases from material degradation in the upper atmosphere. At end-of-life, uncontrolled deorbiting poses risks, including the dispersal of radioactive materials from defunct nuclear-powered satellites. Controlled deorbiting or moving to graveyard orbits aims to mitigate space debris, but the long-term accumulation remains a concern. Deorbiting satellites can also introduce pollutants into the atmosphere.

Material Degradation: Atomic oxygen oxidizes satellite materials, releasing gases like CO and CO₂.
Uncontrolled Deorbit: Risk of pollution and dispersal of hazardous materials (e.g., from nuclear-powered satellites).
Space Debris: Accumulation of defunct satellites and launch vehicle stages poses collision risks (Kessler Syndrome).
Atmospheric Re-entry: Most satellites burn up, but this process can introduce materials and pollutants into the atmosphere.

Night Sky Pollution

The increasing number of satellites, particularly large constellations, is significantly increasing artificial brightness in the night sky. This can affect astronomical observations and potentially disorient nocturnal wildlife that relies on celestial patterns for navigation.

Interference and Threats

Collision Threat

The proliferation of satellites and space debris presents a significant collision risk. The accumulation of tracked objects in orbit threatens existing spacecraft and future space endeavors, potentially leading to a Kessler Syndrome scenario where orbital debris cascades, rendering space unusable.

Space Debris: Fragments from defunct satellites, rocket stages, and anti-satellite tests pose a constant hazard.
Kessler Syndrome: A theoretical scenario where collisions generate more debris, leading to a runaway chain reaction.
Constellation Impact: Large satellite constellations exacerbate the risk due to sheer numbers.
Mitigation Efforts: Focus on responsible deorbiting and debris removal technologies.

Radio Interference

Satellite transmissions are susceptible to jamming from terrestrial transmitters, limited by the transmitter's range. GPS and communication signals can be targeted. Additionally, accidental or intentional transmission interference can disrupt satellite transponder operations, necessitating sophisticated monitoring by satellite operators.

Regulatory Landscape

Governance and Liability

International agreements, such as the Liability Convention, address liability for damage caused by satellites. However, emerging issues like space debris, radio interference, and light pollution face challenges in achieving comprehensive national and international regulatory progress.

Operational Imperatives

Ground Segment and Capabilities

Effective satellite operation requires not only financial, manufacturing, and launch capabilities but also a robust ground segment infrastructure for monitoring and control. The operational scope and utility of satellites continue to broaden significantly with technological advancements.

Notable Satellites by Mass

Satellite Inventory

The following table lists selected Earth satellites by mass, highlighting their operator, primary function, orbit, and operational status. This provides a quantitative overview of significant artificial objects in Earth orbit.

Name	Mass	Operator	Description	Orbit	State	In Service From
Polyus	80,000 kg (176,370 lb)	Soviet Union	Prototype orbital weapons platform	LEO	Lost	1987
KH-11	19,600 kg (43,211 lb)	United States	Electro-optical reconnaissance satellite	SSO	In service	1976– (current version: 2005–)
Proton satellite	17,000 kg (37,479 lb)	Soviet Union	Space research satellite	LEO	Deorbited	1965–1969
Compton Gamma Ray Observatory	16,329 kg (35,999 lb)	United States	Space observatory	LEO	Deorbited	1991–2000
Lacrosse	14,500–16,000 kg (31,967–35,274 lb)	United States	Radar imaging reconnaissance satellite	SSO	Retired (Lacrosse 5 still in orbit)	1988–2005
Hubble Space Telescope	11,110 kg (24,493 lb)	United States	Space observatory	LEO	In service	1990–
Jupiter-3 (EchoStar-24)	9,200 kg (20,283 lb)	United States	Communications satellite	GEO	In service	2023–
Envisat	8,211 kg (18,102 lb)	ESA	Earth observing satellite; Kessler syndrome threat	LEO	In orbit, inoperable	2002–2012
Shijian-20	8,000 kg (17,637 lb)	China	Communication Technology Test Satellite	GEO	In service	2019–
Telstar 19V	7,075 kg (15,598 lb)	Canada	Communications satellite	GEO	In service	2018–
TerreStar-1	6,910 kg (15,234 lb)	United States	Communications satellite	GEO	In service	2009–
EchoStar XXI	6,871 kg (15,148 lb)	United States	Communications satellite	GEO	In service	2017–
UARS	6,540 kg (14,418 lb)	United States	Earth science	LEO	Deorbited 2011	1991–2005
James Webb Space Telescope	6,500 kg (14,330 lb)	United States	Space observatory	Sun-Earth L2	In service	2021–
Chandra X-ray Observatory	5,865 kg (12,930 lb)	United States	Space observatory	HEO	In service	1999–
GSAT-11	5,854 kg (12,906 lb)	India	Heaviest Indian communications satellite	GEO	In service	2018–
Terra	4,864 kg (10,723 lb)	United States	Earth observing satellite	SSO	In service	1999–
GSAT-24	4,181 kg (9,218 lb)	India	Indian Communication Satellite	GEO	In service	2022–
GPS IIIA	3,880 kg (8,554 lb)	United States	Current GPS satellite series	MEO	In service	2018–
Spektr-R (RadioAstron)	3,660 kg (8,069 lb)	Russia	Space observatory	HEO	In service	2011–
Herschel	3,400 kg (7,496 lb)	ESA	Space observatory	Sun-Earth L2	Retired	2009–2013
Astrosat	1,513 kg (3,336 lb)	India	Space observatory from India	LEO	In service	2015–
Malligyong-1	300 kg (661 lb)	North Korea	Heaviest North Korean reconnaissance satellite, 21 Nov 2023 launch	SSO	In service	2023–

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References

to distinguish them from natural satellites.

R. R. Carhart, Scientific Uses for a Satellite Vehicle, Project RAND Research Memorandum. (Rand Corporation, Santa Monica) 12 February 1954.

H. K. Kallmann and W. W. Kellogg, Scientific Use of an Artificial Satellite, Project RAND Research Memorandum. (Rand Corporation, Santa Monica, California) 8 June 1955.

A full list of references for this article are available at the Satellite Wikipedia page

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This content has been generated by Artificial Intelligence and is intended for educational and informational purposes only. It is based on publicly available data and may not reflect the most current or complete information. The information provided is not a substitute for professional consultation in any field, including aerospace engineering, physics, or space policy.

No professional advice is provided. Users should consult official documentation and qualified experts for specific applications or inquiries related to satellite technology, space operations, or environmental regulations.

The creators of this page are not liable for any errors, omissions, or actions taken based on the information presented herein.

Orbital Sentinels

💡 Dive in with Flashcard Learning! 💡

Defining the Artificial Satellite 🛰️

🌌 Celestial Objects in Orbit

🛰️ Diverse Utility

🚀 Reaching Orbit

Historical Trajectory 📜

💡 Early Conceptualizations

🚀 The Dawn of the Space Age

📈 Technological Evolution

Core Components and Systems ⚙️

🧭 Orbit and Attitude Control

⚡ Power Generation and Storage

Diverse Applications 📡

🌍 Earth Observation

📞 Communication

📍 Navigation

🔭 Scientific Observation

🛡️ Military and Experimental

Environmental Considerations 🌳

🏭 Resource Use and Manufacturing

💨 Launch Emissions

♻️ Operational and Deorbit Impacts

✨ Night Sky Pollution

Interference and Threats 💥

☄️ Collision Threat

📡 Radio Interference

Regulatory Landscape ⚖️

📜 Governance and Liability

Operational Imperatives ⚙️

🛰️ Ground Segment and Capabilities

Notable Satellites by Mass 📊

📜 Satellite Inventory

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📜 Important Notice

Dive in with Flashcard Learning!

Defining the Artificial Satellite

Celestial Objects in Orbit

Diverse Utility

Reaching Orbit

Historical Trajectory

Early Conceptualizations

The Dawn of the Space Age

Technological Evolution

Core Components and Systems

Orbit and Attitude Control

Power Generation and Storage

Diverse Applications

Earth Observation

Communication

Navigation

Scientific Observation

Military and Experimental

Environmental Considerations

Resource Use and Manufacturing

Launch Emissions

Operational and Deorbit Impacts

Night Sky Pollution

Interference and Threats

Collision Threat

Radio Interference

Regulatory Landscape

Governance and Liability

Operational Imperatives

Ground Segment and Capabilities

Notable Satellites by Mass

Satellite Inventory

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice