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Synchronous orbit

A synchronous orbit is an orbit around a celestial body in which the orbiting object's period matches the sidereal rotation period of the central body, resulting in the object completing one revolution relative to the fixed stars in the same time the central body rotates once.^[1] For Earth, this period is 23 hours, 56 minutes, and 4 seconds, corresponding to a circular orbital altitude of approximately 35,786 kilometers above the equator.^[2] Synchronous orbits around Earth, commonly referred to as geosynchronous orbits, enable satellites to hover over the same longitude continuously, though the exact ground track varies with orbital inclination.^[3] A special case is the geostationary orbit, which is circular, equatorial (zero inclination), and prograde, causing the satellite to appear motionless in the sky from a fixed point on Earth's surface.^[4] Inclined geosynchronous orbits produce a figure-eight ground track, while elliptical variants allow for more complex paths but still synchronize periods.^[1] These orbits are prized for applications including telecommunications, where satellites relay signals across vast areas without frequent adjustments; meteorological observation, providing continuous regional monitoring; and navigation augmentation, supporting global positioning systems.^[4] As of August 2025, approximately 570 operational satellites occupy geosynchronous slots, managed through international coordination to avoid interference.^[5]

Fundamentals

Definition

A synchronous orbit is an orbit in which the orbital period of a satellite matches the sidereal rotation period of the central body it orbits, such as a planet or moon.^[1] This synchronization ensures that the satellite completes exactly one revolution around the central body in the same time it takes the body to rotate once relative to the fixed stars.^[1] For Earth, the sidereal rotation period is 23 hours, 56 minutes, and 4 seconds (approximately 23.9345 hours), meaning an Earth-orbiting satellite in such an orbit returns to the same position relative to the rotating Earth each sidereal day.^[1] While all synchronous orbits share this period-matching characteristic, they differ from related orbit types like geostationary orbits, which represent a specialized subset.^[1] Geostationary orbits are circular and equatorial (with zero inclination to the body's equator), positioning the satellite directly above a fixed longitude on the surface without apparent east-west drift.^[1] In general, synchronous orbits can have any inclination, allowing for non-equatorial paths while preserving the synchronized period, which broadens their applications beyond fixed-point observation.^[1] From the viewpoint of an observer on the central body's surface, the apparent motion of a satellite in a synchronous orbit varies with its inclination. In a circular equatorial synchronous orbit, the satellite remains stationary in the sky, hovering continuously over the same geographic point.^[1] For circular inclined synchronous orbits, the satellite traces a figure-eight (or analemma) pattern against the background, oscillating in latitude north and south of the equator while staying aligned with the same longitude, creating a predictable daily loop rather than a fixed position.^[6]

Historical background

The concept of synchronous orbits traces its origins to early 20th-century theoretical advancements in rocketry and space travel. In 1903, Russian scientist Konstantin Tsiolkovsky published foundational calculations on achieving Earth orbit using rocket propulsion, laying the groundwork for artificial satellites by determining the necessary velocities for orbital motion.^[7] This work, while not explicitly detailing geostationary configurations, established the mathematical basis for sustained orbits around Earth. Building on such ideas, Slovenian engineer Hermann Potočnik (writing under the pseudonym Hermann Noordung) proposed in his 1928 book Das Problem der Befahrung des Weltraums—der Raketen-Motor a permanent space station in a geosynchronous orbit at approximately 36,000 kilometers altitude, where it would remain fixed relative to Earth's surface to enable continuous observation and communication.^[8] Noordung's design envisioned a rotating wheel-shaped station for artificial gravity, marking the first detailed conceptualization of a synchronous orbital platform.^[9] By the mid-20th century, these theoretical notions evolved toward practical applications in telecommunications. In October 1945, British author and engineer Arthur C. Clarke outlined in his article "Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?" published in Wireless World, the use of a constellation of three manned geostationary satellites spaced 120 degrees apart in equatorial orbit to relay global radio and television signals without the need for ground-based infrastructure.^[10] Clarke's proposal highlighted the strategic altitude matching Earth's rotation period, predicting its feasibility within 50 years through advancements in rocketry. Complementing this, American engineer John R. Pierce independently refined the concept in a 1954 speech to the U.S. Air Force and subsequent 1955 article, advocating passive and active satellites—including those in synchronous orbits—as relays for transcontinental communications, emphasizing microwave transmission viability.^[11] Pierce's contributions shifted focus from manned stations to unmanned satellites, influencing early NASA programs.^[12] The realization of synchronous orbits followed the dawn of the Space Age. The Soviet Union's launch of Sputnik 1 on October 4, 1957, marked the first artificial satellite, orbiting Earth in approximately 98 minutes in a low elliptical path, serving as a non-synchronous precursor that demonstrated orbital technology but underscored the challenges of achieving longer periods.^[13] NASA's Syncom program advanced this rapidly; Syncom 2, launched on July 26, 1963, became the world's first operational geosynchronous satellite, positioned at about 35,900 kilometers altitude with a 24-hour orbital period, enabling real-time transatlantic voice and data transmission despite its initial inclined orbit.^[14] During the 1960s, engineers recognized the utility of inclined synchronous orbits to extend coverage beyond equatorial regions, accommodating launch site latitudes and providing broader hemispheric visibility without full equatorial alignment. This approach, evident in early Syncom missions, facilitated applications like military communications and weather monitoring, evolving the concept from theoretical fixed points to flexible orbital configurations.^[11]

Types

Geosynchronous orbits

A geosynchronous orbit is an Earth-centered orbit with an orbital period that matches Earth's sidereal rotation period of 23 hours, 56 minutes, and 4 seconds.^[4] This altitude places satellites approximately 35,786 kilometers above Earth's surface, enabling them to synchronize their motion with the planet's rotation.^[3] Geosynchronous orbits encompass several subtypes, with geostationary orbits (GEO) representing the equatorial variant. In a GEO, the orbit is circular with zero inclination relative to Earth's equator, causing the satellite to remain fixed over a specific longitude on the surface, appearing motionless to ground observers.^[15] Geosynchronous inclined orbits, by contrast, feature a non-zero inclination, resulting in the satellite tracing a figure-8 or analemma pattern in the sky as viewed from Earth, oscillating north and south of the equator while completing one orbit per sidereal day.^[16] These orbits offer key advantages for Earth-based applications, including continuous visibility from ground stations without the need for tracking antennas, as the satellite maintains a consistent position relative to the observer.^[3] For geostationary configurations, three evenly spaced satellites can achieve near-global coverage of Earth's surface, excluding polar regions.^[3] The standard nomenclature distinguishes geosynchronous orbits (GSO) as the broader category, while GEO specifically denotes the equatorial, stationary subtype.^[15] Unlike synchronous orbits around other celestial bodies, such as the Moon or planets, geosynchronous orbits are uniquely defined by synchronization with Earth's rotation.^[4]

Non-geosynchronous synchronous orbits

Synchronous orbits around the Moon, known as lunasynchronous orbits, feature an orbital period matching the Moon's sidereal rotation period of approximately 27.3 days, allowing a satellite to remain fixed relative to a point on the lunar surface.^[17] However, due to significant perturbations from Earth's gravity, traditional circular lunasynchronous orbits require continuous propulsion for stability, making them impractical for long-duration missions without advanced station-keeping. Beyond the Moon, synchronous orbits are conceptualized for other planets, adapting to their unique rotation periods and gravitational environments. For Mars, an areosynchronous orbit has a period of about 24.6 hours, matching the planet's sidereal day of 88,642 seconds, enabling satellites to hover over the same longitude while allowing latitudinal drift for broader coverage.^[18] Around Jupiter, a joviansynchronous orbit aligns with the planet's rapid rotation period of approximately 9.93 hours (9 hours, 55 minutes, 30 seconds), positioning satellites at a radius of about 160,000 km to support potential relay or observation missions, though no operational examples exist due to the intense radiation belts.^[19]^[20] A specialized subtype is the areostationary orbit around Mars, which is both areosynchronous and equatorial with zero inclination, resulting in a satellite appearing stationary at a fixed position above the surface at an altitude of roughly 17,000 km (semi-major axis of 20,428 km).^[18] This configuration supports continuous observation of the entire Martian disk, ideal for telecommunications relays or weather monitoring, though it demands precise station-keeping to counteract drifts from the planet's oblateness and solar influences.^[18] Establishing synchronous orbits around non-Earth bodies presents distinct challenges, primarily stemming from weaker gravitational fields that necessitate significantly larger orbital radii to achieve the required period, increasing vulnerability to solar radiation pressure and external perturbations.^[20] Tidal locking, prevalent among natural satellites, further complicates dynamics; for instance, Mars' moon Phobos experiences strong tidal forces that cause its orbit to decay inward at about 1.8 meters per century, highlighting how such effects can destabilize nearby artificial orbits without robust propulsion systems.^[21] These factors demand higher delta-v budgets for maintenance compared to Earth orbits, limiting mission durations unless advanced electric propulsion is employed.^[18]

Characteristics

Key properties

Synchronous orbits are characterized by an orbital period that matches the sidereal rotation period of the central body, resulting in a specific orbital radius determined by the body's mass and rotation rate. For Earth, this corresponds to a geosynchronous orbital radius of approximately 42,164 km from the center of the Earth, or an altitude of about 35,786 km above the surface.^[22] In general, the orbital radius scales as the cube root of the gravitational parameter (GM) of the central body and the two-thirds power of the rotation period, leading to proportionally higher altitudes for bodies with greater mass or slower rotation.^[23] The orbital velocity in a circular synchronous orbit remains constant and is given by the balance between gravitational attraction and centripetal force. For Earth's geostationary orbit, this velocity is approximately 3.07 km/s, significantly lower than in low Earth orbit due to the greater distance from the central body. This slower speed reflects the inverse square root dependence on orbital radius in Keplerian mechanics.^[24] Inclination plays a critical role in the apparent motion of satellites in synchronous orbits. A zero-degree inclination aligns the orbit with the equatorial plane, enabling a geostationary position where the satellite remains fixed relative to a point on the surface. Non-zero inclinations introduce a daily north-south oscillation in the satellite's ground track, with the amplitude equal to the inclination angle, causing the satellite to trace an analemma or figure-eight pattern as viewed from the surface.^[25] Synchronous orbits provide fixed longitude coverage over the central body's surface, with the satellite appearing stationary in longitude but potentially moving in latitude if inclined. Visibility from the surface is limited by the geometry of the orbit; for Earth's geostationary orbit, ground stations can see the satellite up to approximately 81° latitude, beyond which it dips below the horizon. This coverage footprint is roughly a circular region centered on the subsatellite point, with an angular radius of about 81° from the observer's perspective.^[26] Inserting a spacecraft into a synchronous orbit requires substantially higher delta-v compared to low Earth orbit due to the elevated altitude and the need for a transfer orbit, such as a Hohmann transfer. For Earth, the additional delta-v from low Earth orbit to geosynchronous orbit typically totals around 3.9 km/s, including burns for apogee raise and circularization, far exceeding the energy needs for low-altitude circularization. This increased requirement stems from the deeper gravitational well and longer propagation times in the transfer phase.^[27]

Stability and perturbations

Synchronous orbits, particularly geostationary Earth orbits (GEO) at an altitude of approximately 35,786 km, experience gravitational perturbations primarily from the Moon and Sun, which induce oscillations in eccentricity and inclination. These luni-solar effects cause a gradual growth in orbital eccentricity over time, potentially leading to perigee excursions that require corrective maneuvers to prevent atmospheric re-entry risks for slightly eccentric orbits.^[28]^[29] Additionally, Earth's oblateness, characterized by the J2 gravitational harmonic, results in nodal precession of the orbital plane around the Earth's axis, with the rate depending on the orbit's inclination and semimajor axis.^[30] Atmospheric drag in synchronous orbits is negligible due to the high altitude well above the significant exosphere density, which primarily affects low Earth orbits below 2,000 km.^[31] In contrast, solar radiation pressure exerts a continuous force on satellites, inducing longitudinal drift and eccentricity variations by accelerating the spacecraft along the Sun-Earth line, with effects amplified for satellites with large area-to-mass ratios.^[32] To counteract these perturbations, satellites in GEO perform regular station-keeping maneuvers using onboard chemical or electric propulsion systems, consuming propellant to maintain desired longitude and inclination within operational boxes typically of 0.05° to 1°. These maneuvers address longitude drifts from Earth's triaxiality and inclination changes from luni-solar and radiation forces, with typical GEO satellites designed for a 15-year operational lifespan supported by approximately 50 m/s delta-v budget per year (totaling around 750 m/s over the lifespan) for such controls.^[32]^[33] At end-of-life, international guidelines from the Inter-Agency Space Debris Coordination Committee (IADC) require GEO satellites to be disposed into graveyard orbits with a perigee at least 300 km above the GEO altitude to avoid interference with the protected GEO region, ensuring long-term stability without re-entering the operational belt.^[34]^[35] Inclined synchronous orbits exhibit heightened sensitivity to perturbations compared to equatorial GEO, as the increased inclination amplifies luni-solar and oblateness effects on eccentricity and node regression, often necessitating more frequent station-keeping. For non-Earth examples, such as areosynchronous orbits around Mars, the thin atmosphere results in virtually no drag perturbations, but solar radiation pressure remains a dominant influence, exerting forces one-third to one-half those in Earth's GEO due to Mars' greater distance from the Sun.^[36]^[37]

Mathematics

Orbital period derivation

The derivation of the orbital period for a synchronous orbit begins with Kepler's third law, which states that the square of the orbital period T of a body is proportional to the cube of the semi-major axis a of its orbit, expressed as T^2 \propto a^3.^[38] This empirical law, originally formulated for planetary motion around the Sun, applies to any two-body system under gravitational influence, including artificial satellites orbiting a central body like Earth. To derive the specific form for synchronous orbits, consider the idealized two-body problem where the satellite orbits a much more massive central body, assuming a circular orbit and neglecting perturbations such as atmospheric drag or non-spherical gravitational fields. The gravitational force provides the centripetal acceleration, leading to the orbital speed v = \sqrt{GM / a}, where G is the gravitational constant and M is the mass of the central body. The orbital period T is then the circumference divided by the speed: T = 2\pi a / v = 2\pi \sqrt{a^3 / GM}.^[39] Squaring both sides yields Kepler's third law in its Newtonian form: T^2 = (4\pi^2 / GM) a^3.^[40] For a synchronous orbit, the satellite's orbital period must match the sidereal rotation period T_\mathrm{rot} of the central body to maintain a fixed position relative to the rotating surface. Setting T = T_\mathrm{rot} in the equation and solving for the semi-major axis (which equals the orbital radius a for a circular orbit) gives:

a = \left[ \frac{G M T_\mathrm{rot}^2}{4 \pi^2} \right]^{1/3}.

^[41] This formula establishes the precise radius required for synchrony, confirming that such orbits exist at a unique distance determined by the central body's mass and rotation rate.^[39] This derivation underpinned early predictions of geostationary orbits, as articulated by Arthur C. Clarke in his 1945 paper, where he applied Kepler's law to propose satellites at approximately 36,000 km altitude for global communications by matching Earth's rotation period.^[42]

Radius and inclination formulas

The semi-major axis a of a synchronous orbit, which equals the orbital radius for the typically circular case, is derived from Kepler's third law by setting the orbital period equal to the central body's sidereal rotation period T_{\text{rot}}. The formula is

a = \left( \frac{\mu T_{\text{rot}}^2}{4 \pi^2} \right)^{1/3},

where \mu = G M is the standard gravitational parameter of the central body (with G the gravitational constant and M the body's mass).^[43] The corresponding altitude h is obtained by subtracting the body's mean radius R from a, yielding h = a - R. For Earth-specific applications, this formula gives a \approx 42{,}164 km (corresponding to an altitude of approximately 35{,}786 km above the equatorial radius of 6{,}378 km).^[44] Body-specific adaptations account for differences in \mu and T_{\text{rot}}; for Mars, with its lower \mu \approx 4.282 \times 10^{13} m³/s² and longer sidereal day T_{\text{rot}} \approx 88{,}640 s, the synchronous radius is a \approx 20{,}428 km (altitude approximately 17{,}031 km above Mars's mean radius of 3{,}397 km).^[45] The orbital inclination i has no effect on the semi-major axis a required for synchrony, since the period depends only on a and \mu (for zero eccentricity). However, inclination alters the ground track from a fixed point (at i = 0^\circ) to an analemma—a figure-eight pattern traced by the subsatellite point over one rotation period. In this configuration, the satellite oscillates perpendicular to the equatorial plane with a maximum north-south excursion of $2 a \sin i, which projects onto the surface to limit the ground track's latitudinal extent to \pm i.^[46] For inclined synchronous orbits, the satellite's position is parameterized by the true anomaly \nu, the angle from perigee in the orbital plane (which for circular orbits serves as a phase angle from a reference direction), enabling computation of coordinates via standard orbital elements.

Applications

Satellite communications

Synchronous orbits, particularly geosynchronous Earth orbits (GEO), form the backbone of global satellite communications infrastructure, supporting television broadcasting, internet access, and telephony services. A single GEO satellite provides coverage to approximately one-third of Earth's surface visible from space, enabling three satellites spaced 120 degrees apart to deliver near-global connectivity excluding extreme polar areas.^[47] Prominent fleets, such as Intelsat's, have historically driven this capability; Intelsat I (Early Bird), launched in 1965, marked the first commercial communications satellite in synchronous orbit, revolutionizing transatlantic television transmission.^[48] Similarly, SES operates a extensive array of GEO satellites to facilitate broadband internet and video distribution, serving remote and underserved regions worldwide.^[49] These orbits offer significant advantages for telecommunications, primarily the stationary appearance of satellites relative to ground observers, which allows the use of fixed, non-tracking antennas at earth stations.^[50] This fixed positioning also minimizes Doppler shift in transmitted signals, as the satellites maintain near-constant velocity and distance from receivers, thereby reducing frequency variations and simplifying modulation and demodulation processes in communication systems.^[51] However, the substantial altitude of synchronous orbits introduces challenges, including signal propagation latency, with round-trip times of approximately 250 ms for GEO links due to the 36,000 km distance.^[52] Such delays can impair interactive applications like voice calls or online gaming, though they are tolerable for broadcasting and data transfer. To mitigate coverage gaps at higher latitudes, where equatorial GEO satellites become invisible below the horizon, inclined geosynchronous orbits are utilized; these allow satellites to oscillate north-south in a figure-eight ground track, extending visibility and service to regions up to about 70 degrees latitude.^[53] The development of synchronous orbit communications traces back to the Syncom program, with Syncom 2 achieving the first operational geosynchronous communications satellite in July 1963, demonstrating trans-Pacific telephony and television relay.^[54] This success spurred international collaboration, leading to the establishment of Intelsat in 1964 and subsequent expansions by operators like SES in the 1980s. Overseeing this growth, the International Telecommunication Union (ITU) regulates geostationary orbital slots through frequency coordination and registration processes, allocating positions along the equatorial arc to avoid interference and promote equitable spectrum use among nations.^[55]

Scientific and other uses

Synchronous orbits, particularly geostationary Earth orbits (GEO), enable continuous monitoring of space weather phenomena, such as solar flares and coronal mass ejections, which can impact Earth's magnetosphere and technological infrastructure. The Geostationary Operational Environmental Satellites (GOES), operated by NOAA and NASA, are positioned in GEO to provide real-time observations of solar activity and geomagnetic storms using instruments like the Solar Ultraviolet Imager and Space Environment In-Situ Suite. These satellites deliver data critical for forecasting space weather events, supporting aviation, power grids, and satellite operations by offering persistent views of the sunward direction without the need for orbital adjustments.^[56]^[57] In navigation systems, GEO satellites augment global positioning networks by broadcasting integrity and correction signals to enhance accuracy and reliability. The Wide Area Augmentation System (WAAS), developed by the FAA, utilizes a constellation of GEO satellites to transmit differential corrections and integrity monitoring data derived from ground reference stations, compensating for GPS signal errors due to ionospheric delays and satellite ephemeris inaccuracies. This augmentation achieves vertical accuracy better than 1 meter in aviation applications, enabling precision approaches in the National Airspace System while ensuring rapid detection of any GPS anomalies.^[58]^[59] Military applications leverage the persistent overhead coverage of GEO for intelligence, surveillance, and reconnaissance (ISR), particularly in missile defense and early warning. The Space Based Infrared System (SBIRS), a U.S. Space Force program, deploys GEO satellites equipped with scanning and staring infrared sensors to detect heat signatures from ballistic missile launches, providing global, near-real-time alerts with improved sensitivity over previous systems. This fixed vantage point allows for continuous "stare" capability over key regions, facilitating rapid threat characterization and cueing of ground-based defenses, as demonstrated in operations tracking hundreds of missile events annually.^[60]^[61] Beyond Earth, synchronous orbits around other celestial bodies have been proposed for scientific missions requiring stable relay or observation platforms. For Mars, areosynchronous orbits—synchronous with the planet's 24.6-hour rotation—offer potential for communication relays in future human exploration, enabling consistent data links between surface assets and Earth without frequent orbital passes, as outlined in relay strategies for missions through 2030. Similarly, lunastationary orbits, matching the Moon's sidereal day, have been conceptualized for telescope pointing in lunar missions to maintain fixed views of specific surface features or deep-space targets, though stability challenges from lunar mascons necessitate active control.^[62] Emerging scientific uses include quantum communication experiments exploiting GEO's stable platform for long-distance key distribution. Experiments with GEO satellites, such as those using Alphasat, have tested quantum-limited optical signal reception, achieving bounds on quantum efficiency for secure photon transmission over thousands of kilometers.^[63] Recent developments, such as the QKD-GEO initiative by Thales Alenia Space and Hispasat, aim to deploy GEO-based quantum key distribution systems for unbreakable encryption in global networks, building on ground-to-satellite demonstrations of entanglement distribution. These efforts highlight synchronous orbits' role in advancing quantum-secure infrastructures against eavesdropping threats.^[64]^[65]

Notable examples

One of the earliest successful demonstrations of a geosynchronous orbit was NASA's Syncom 2 satellite, launched on July 26, 1963, which became the first spacecraft to achieve and operate in such an orbit, enabling real-time communication tests including a transatlantic phone call by President Kennedy.^[14] This paved the way for commercial applications, exemplified by Intelsat I (Early Bird), launched on April 6, 1965, as the first commercial geosynchronous communications satellite, providing transatlantic television broadcasts and telephone services.^[66] The Intelsat series represents a cornerstone of modern geosynchronous fleets, with operations beginning in 1965; following acquisition by SES in July 2025, the combined fleet exceeds 120 satellites as of November 2025, delivering global broadband, television, and maritime communications from equatorial geostationary positions.^[48]^[67] Similarly, Brazil's Star One C2, launched on April 18, 2008, exemplifies regional geostationary capabilities, operating from 65° W to provide C-band and Ku-band services for telecommunications, internet, and digital TV across South America, Mexico, and parts of the United States.^[68] Beyond Earth, synchronous orbit concepts have been adapted for other celestial bodies. NASA's 2001 Mars Odyssey orbiter, launched on April 7, 2001, supports long-duration mapping and relay functions from its low polar orbit.^[69] The Lunar Reconnaissance Orbiter (LRO), launched on June 18, 2009, employs a polar mapping orbit to aid detailed lunar surface characterization.^[70] Recent advancements include Viasat-3 satellites, with the first (ViaSat-3 F1) launched on May 30, 2023, to geostationary orbit at 115° W, delivering over 1 Tbps of high-throughput Ka-band capacity for global broadband, aviation Wi-Fi, and mobility services; the second (ViaSat-3 F2) was launched on November 13, 2025, targeting Europe, the Middle East, and Africa from 69° E.^[71]^[72] China's Queqiao-2 relay satellite, launched on March 20, 2024, operates in a synchronous-like halo orbit around the Earth-Moon L2 Lagrange point, enabling continuous communication with the lunar far side for missions like Chang'e-6 sample return.^[73] Decommissioned satellites often transition to graveyard orbits to mitigate collision risks. For instance, AT&T's Telstar 301, launched in 1983 and retired in 1993 after a decade of Ku-band service over the Americas, was maneuvered to a super-synchronous disposal orbit above the geostationary belt, where it remains inactive.

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May 2, 2024 · Kepler's Third Law: The orbital period of a planet, squared, is directly proportional to the semi-major axes of its orbit, cubed. This is ...Orbits And Kepler's Laws · Kepler And The Mars Problem · Here Are Kepler's Three Laws
[39]
Kepler's Third Law - Physics
Kepler's Third Law relates the period of an orbit to the radius of an orbit, if the orbit is circular, and to the semimajor axis if the orbit is elliptical.
[40]
Kepler's 3rd Law--Lesson Plan #31 - PWG Home - NASA
Oct 23, 2004 · A simple formula for the orbital period in a circular Earth orbit of given radius. Terms: Orbital velocity, escape velocity, synchronous orbit.
[41]
Mathematics of Satellite Motion - The Physics Classroom
As seen in the equation v = SQRT(G * Mcentral / R), the mass of the central body (earth) and the radius of the orbit affect orbital speed. The orbital radius is ...Orbital Speed Equation · Orbital Period Equation · Example Problems
[42]
The 1945 Proposal by Arthur C. Clarke for Geostationary Satellite ...
Clarke's most famous prediction on the future is his proposal of geostationary satellite communications published in the Wireless World magazine in 1945.
[43]
Geosynchronous Orbit
To find out, equate the force of gravity at a certain earth-satellite distance to the centripetal force needed to keep it in orbit with a 24-hour period.
[44]
[PDF] Earth Coverage by Satellites in Circular Orbit - Faculty
If GPS satellites were synchronous (24 hour orbit), r would be. 42,164 km ... A satellite's inclination (I) is the angle between Earth's equatorial plane and the ...
[45]
[PDF] Evolvable Mars Campaign Development
May 24, 2016 · Areosynchronous radius = 20428 km. Deimos semimajor axis = 23463 km ... 1 Sol x 250 km Orbit. Spacecraft Remains in. Elliptical Orbit.
[46]
3.5 Orbital Mechanics – A Guide to CubeSat Mission and Bus Design
Determine the following characteristics of the orbit: inclination (i), period (P), semi-major axis (a), altitude (z), satellite's orbital speed ( v_c ) ...Missing: properties | Show results with:properties
[47]
[PDF] Basics of satellite communications - ITSO
advantages: ✓ One satellite can cover almost 1/3 of Earth's surface, offering a reach far more extensive than what any terrestrial network can achieve.
[48]
Intelsat History
Early Bird (Intelsat I) is launched into synchronous orbit. This is the world's first commercial communications satellite and “live via satellite” is born.
[49]
SES | Satellite Communication Service Provider
SES helps deliver broadband connectivity and end-to-end video services to rural and remote areas that are often difficult to reach.About Us · Our Offices · SES & Intelsat: Better for the... · Our Coverage
[50]
Satellite Basics | Intelsat
Only one GEO satellite is needed to provide connection to a fixed spot on the earth, and only 3 are needed at equal distances to provide coverage to the whole ...Parts Of A Satellite And... · Understanding Orbits · Frequencies
[51]
GEO Satellite Orbit: Advantages and Disadvantages
Minimal Doppler Shift: Reduces complexity in receiver design for satellite communication, as there is almost no doppler shift. Disadvantages of GEO ...
[52]
Geostationary satellite latency and time delay ms - SatSig.net
O3b claim a round trip latency of better then 150mS. 150 mS round trip refers to a double hop distance of 11250 + 11250 + 11250 + 11250 km. Proposed OneWeb ...
[53]
Geosynchronous inclined orbits for high-latitude communications
We present a detailed analysis of a group of geosynchronous, highly inclined orbits for telecommunication satellites. The analysis includes the orbital ...Geosynchronous Inclined... · Introduction · Station KeepingMissing: oscillation | Show results with:oscillation
[54]
Communications Satellite, Syncom A
In a historic first, Syncom 3 transmitted television signals of the 1964 Olympic games in Tokyo to the United States. Geostationary satellites still provide the ...
[55]
Regulation of satellite systems - ITU
ITU regulates satellite systems by overseeing frequency allocation, managing registration, and ensuring no harmful interference, through international ...
[56]
Geostationary Satellites | NESDIS - NOAA
The GOES-R Series provides advanced imagery and atmospheric measurements, real-time mapping of lightning activity, and monitoring of space weather.Noaa's Goes-R Series · Monitoring Weather On Earth... · Other Resources
[57]
GOES Satellite Network - NASA Science
GOES satellites orbit 22,236 miles above Earth's equator, at speeds equal to the Earth's rotation. This allows them to maintain their positions over specific ...
[58]
Satellite Navigation - WAAS - How It Works
The WAAS provides navigation services across all of the National Airspace System (NAS). The WAAS provides augmentation information to GPS/WAAS receivers.
[59]
WAAS Space Segment - Navipedia - GSSC
The Wide Area Augmentation System (WAAS) is the United States Satellite Based Augmentation System. The programme, started in 1992, is being carried out by ...<|separator|>
[60]
Space Based Infrared System > United States Space Force > Fact ...
SBIRS is a follow-on to DSP, using space-based satellites and ground systems for missile early warning, defense, and intelligence, with enhanced infrared ...
[61]
SBIRS: Early Missile Warning System - Lockheed Martin
The system includes a combination of satellites and hosted payloads in Geosynchronous Earth Orbit (GEO) and Highly Elliptical Orbit (HEO) and ground hardware ...
[62]
Relay communications strategies for Mars exploration through 2020
Aug 6, 2025 · Relay telecommunication via Mars-orbiting spacecraft offers significant advantages in meeting these challenges, relative to conventional direct- ...
[63]
[PDF] Deep Space Gateway Concept Science Workshop
Mar 1, 2018 · Rapetti D. The Gateway to Cosmic Dawn: A Low Frequency Radio Telescope for the Deep. Space Gateway [#3096]. We suggest that, with a suitable ...
[64]
Quantum-limited measurements of optical signals from a ...
This work presents and discusses quantum-limited measurements on optical signals sent from a geostationary satellite. We report on the first bound of the ...
[65]
Thales Alenia Space and Hispasat start the development of the ...
Jan 21, 2025 · The QKD-GEO project comprises the development of the various components for a future quantum key distribution system from geostationary orbit.Missing: experiments | Show results with:experiments
[66]
Satellite-based quantum information networks: use cases ... - Nature
Jan 16, 2023 · In the present paper, we focus on such a satellite-based QIN, arguably the most ambitious goal of quantum communications, while remaining close ...
[67]
Meet Intelsat 1
Intelsat 1, also known as Early Bird, was the first commercial communications satellite to launch in geosynchronous orbit.
[68]
Star One C1, C2 - Gunter's Space Page
Jun 2, 2025 · Star One C1 replaces the Brasilsat B2 satellite in the C band and provides South America with high speed Internet and multimedia capacity. In ...Missing: 2002 | Show results with:2002
[69]
Mars Odyssey - NASA Science
Oct 24, 2001 · NASA's 2001 Mars Odyssey mission created the first global map of chemical elements and minerals that make up the Martian surface.Instruments · Highlights · Overview · News & Features
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Lunar Reconnaissance Orbiter - NASA Science
Jun 18, 2009 · The orbiter has mapped the Moon's surface and measured its temperature, composition, and radiation environment in unprecedented detail. Data ...About LRO Mission · LRO Science · Data Products · LRO StoriesMissing: synchronous | Show results with:synchronous
[71]
ViaSat-3: Ultra-high-capacity satellites
The 44-minute launch window opens at 10:04 p.m. EST. Once in service, VS-3 F2 is expected to more than double the bandwidth capacity of Viasat's entire existing ...
[72]
China launches new relay satellite for Earth-Moon communications
Mar 20, 2024 · China launched a new relay satellite on Wednesday to provide Earth-Moon communications services, a key step for its future lunar exploration missions.Missing: synchronous | Show results with:synchronous
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Telstar 301 - Wikipedia
The satellite was retired in 1993 and replaced by Telstar 401. As of June 2009, Telstar 301 (along with Telstar 302 and Telstar 303) was still in orbit.Missing: 1990s | Show results with:1990s