Geosynchronous orbit

Last updated

Animation (not to scale) showing geosynchronous satellite orbiting the Earth Geosynchronous orbit.gif
Animation (not to scale) showing geosynchronous satellite orbiting the Earth

A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object's position in the sky may remain still or trace out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity. A circular geosynchronous orbit has a constant altitude of 35,786 km (22,236 mi). [1]

Contents

A special case of geosynchronous orbit is the geostationary orbit (often abbreviated GEO), which is a circular geosynchronous orbit in Earth's equatorial plane with both inclination and eccentricity equal to 0. A satellite in a geostationary orbit remains in the same position in the sky to observers on the surface. [1]

Communications satellites are often given geostationary or close-to-geostationary orbits, so that the satellite antennas that communicate with them do not have to move but can be pointed permanently at the fixed location in the sky where the satellite appears. [1]

History

The geosynchronous orbit was popularised by the science fiction author Arthur C. Clarke, and is thus sometimes called the Clarke Orbit. Clarke sm.jpg
The geosynchronous orbit was popularised by the science fiction author Arthur C. Clarke, and is thus sometimes called the Clarke Orbit.

In 1929, Herman Potočnik described both geosynchronous orbits in general and the special case of the geostationary Earth orbit in particular as useful orbits for space stations. [2] The first appearance of a geosynchronous orbit in popular literature was in October 1942, in the first Venus Equilateral story by George O. Smith, [3] but Smith did not go into details. British science fiction author Arthur C. Clarke popularised and expanded the concept in a 1945 paper entitled Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage?, published in Wireless World magazine. Clarke acknowledged the connection in his introduction to The Complete Venus Equilateral. [4] [5] The orbit, which Clarke first described as useful for broadcast and relay communications satellites, [5] is sometimes called the Clarke Orbit. [6] Similarly, the collection of artificial satellites in this orbit is known as the Clarke Belt. [7]

Syncom 2: The first functional geosynchronous satellite Syncom 2 side.jpg
Syncom 2: The first functional geosynchronous satellite

In technical terminology, the geosynchronous orbits are often referred to as geostationary if they are roughly over the equator, but the terms are used somewhat interchangeably. [8] [9] Specifically, geosynchronous Earth orbit (GEO) may be a synonym for geosynchronous equatorial orbit , [10] or geostationary Earth orbit. [11]

The first geosynchronous satellite was designed by Harold Rosen while he was working at Hughes Aircraft in 1959. Inspired by Sputnik 1, he wanted to use a geostationary (geosynchronous equatorial) satellite to globalise communications. Telecommunications between the US and Europe was then possible between just 136 people at a time, and reliant on high frequency radios and an undersea cable. [12]

Conventional wisdom at the time was that it would require too much rocket power to place a satellite in a geosynchronous orbit and it would not survive long enough to justify the expense, [13] so early efforts were put towards constellations of satellites in low or medium Earth orbit. [14] The first of these were the passive Echo balloon satellites in 1960, followed by Telstar 1 in 1962. [15] Although these projects had difficulties with signal strength and tracking that could be solved through geosynchronous satellites, the concept was seen as impractical, so Hughes often withheld funds and support. [14] [12]

By 1961, Rosen and his team had produced a cylindrical prototype with a diameter of 76 centimetres (30 in), height of 38 centimetres (15 in), weighing 11.3 kilograms (25 lb); it was light, and small, enough to be placed into orbit by then-available rocketry, was spin stabilised and used dipole antennas producing a pancake-shaped waveform. [16] In August 1961, they were contracted to begin building the working satellite. [12] They lost Syncom 1 to electronics failure, but Syncom 2 was successfully placed into a geosynchronous orbit in 1963. Although its inclined orbit still required moving antennas, it was able to relay TV transmissions, and allowed for US President John F. Kennedy to phone Nigerian prime minister Abubakar Tafawa Balewa from a ship on August 23, 1963. [14] [17]

Today there are hundreds of geosynchronous satellites providing remote sensing, navigation and communications. [12] [1]

Although most populated land locations on the planet now have terrestrial communications facilities (microwave, fiber-optic), which often have latency and bandwidth advantages, and telephone access covering 96% of the population and internet access 90% as of 2018, [18] some rural and remote areas in developed countries are still reliant on satellite communications. [19] [20]

Types

Geostationary orbit

The geostationary satellite (green) always remains above the same marked spot on the equator (brown). Geostat.gif
The geostationary satellite (green) always remains above the same marked spot on the equator (brown).

A geostationary equatorial orbit (GEO) is a circular geosynchronous orbit in the plane of the Earth's equator with a radius of approximately 42,164 km (26,199 mi) (measured from the center of the Earth). [21] :156 A satellite in such an orbit is at an altitude of approximately 35,786 km (22,236 mi) above mean sea level. It maintains the same position relative to the Earth's surface. If one could see a satellite in geostationary orbit, it would appear to hover at the same point in the sky, i.e., not exhibit diurnal motion, while the Sun, Moon, and stars would traverse the skies behind it. Such orbits are useful for telecommunications satellites. [22]

A perfectly stable geostationary orbit is an ideal that can only be approximated. In practice the satellite drifts out of this orbit because of perturbations such as the solar wind, radiation pressure, variations in the Earth's gravitational field, and the gravitational effect of the Moon and Sun, and thrusters are used to maintain the orbit in a process known as station-keeping. [21] :156

Eventually, without the use of thrusters, the orbit will become inclined, oscillating between 0° and 15° every 55 years. At the end of the satellite's lifetime, when fuel approaches depletion, satellite operators may decide to omit these expensive manoeuvres to correct inclination and only control eccentricity. This prolongs the life-time of the satellite as it consumes less fuel over time, but the satellite can then only be used by ground antennas capable of following the N-S movement. [21] :156

Geostationary satellites will also tend to drift around one of two stable longitudes of 75° and 255° without station keeping. [21] :157

Elliptical and inclined geosynchronous orbits

A quasi-zenith satellite orbit Qzss-45-0.09.jpg
A quasi-zenith satellite orbit

Many objects in geosynchronous orbits have eccentric and/or inclined orbits. Eccentricity makes the orbit elliptical and appear to oscillate E-W in the sky from the viewpoint of a ground station, while inclination tilts the orbit compared to the equator and makes it appear to oscillate N-S from a groundstation. These effects combine to form an analemma (figure-8). [21] :122

Satellites in elliptical/eccentric orbits must be tracked by steerable ground stations. [21] :122

Tundra orbit

The Tundra orbit is an eccentric geosynchronous orbit, which allows the satellite to spend most of its time dwelling over one high latitude location. It sits at an inclination of 63.4°, which is a frozen orbit, which reduces the need for stationkeeping. [23] At least two satellites are needed to provide continuous coverage over an area. [24] It was used by the Sirius XM Satellite Radio to improve signal strength in the northern US and Canada. [25]

Quasi-zenith orbit

The Quasi-Zenith Satellite System (QZSS) is a four-satellite system that operates in a geosynchronous orbit at an inclination of 42° and a 0.075 eccentricity. [26] Each satellite dwells over Japan, allowing signals to reach receivers in urban canyons then passes quickly over Australia. [27]

Launch

Animation of EchoStar XVII trajectory.gif
Animation of EchoStar XVII trajectory Equatorial view.gif
An example of a transition from Geostationary Transfer Orbit (GTO) to Geosynchronous Orbit (GSO):
   EchoStar XVII  ·   Earth .

Geosynchronous satellites are launched to the east into a prograde orbit that matches the rotation rate of the equator. The smallest inclination that a satellite can be launched into is that of the launch site's latitude, so launching the satellite from close to the equator limits the amount of inclination change needed later. [28] Additionally, launching from close to the equator allows the speed of the Earth's rotation to give the satellite a boost. A launch site should have water or deserts to the east, so any failed rockets do not fall on a populated area. [29]

Most launch vehicles place geosynchronous satellites directly into a geosynchronous transfer orbit (GTO), an elliptical orbit with an apogee at GSO height and a low perigee. On-board satellite propulsion is then used to raise the perigee, circularise and reach GSO. [28] [30]

Once in a viable geostationary orbit, spacecraft can change their longitudinal position by adjusting their semi-major axis such that the new period is shorter or longer than a sidereal day, in order to effect an apparent "drift" Eastward or Westward, respectively. Once at the desired longitude, the spacecraft's period is restored to geosynchronous. [31]

Proposed orbits

Statite proposal

A statite is a hypothetical satellite that uses radiation pressure from the Sun against a solar sail to modify its orbit. [32]

It would hold its location over the dark side of the Earth at a latitude of approximately 30 degrees. It would return to the same spot in the sky every 24 hours from an Earth-based viewer's perspective, so be functionally similar to a geosynchronous orbit. [32] [33]

Space elevator

A further form of geosynchronous orbit is the theoretical space elevator. When one end is attached to the ground, for altitudes below the geostationary belt the elevator maintains a shorter orbital period than by gravity alone. [34]

Retired satellites

A computer-generated image of space debris. Two debris fields are shown: around geosynchronous space and low Earth orbit. Debris-GEO1280.jpg
A computer-generated image of space debris. Two debris fields are shown: around geosynchronous space and low Earth orbit.

Geosynchronous satellites require some station-keeping in order to remain in position, and once they run out of thruster fuel and are no longer useful they are moved into a higher graveyard orbit. It is not feasible to deorbit geosynchronous satellites, for to do so would take far more fuel than would be used by slightly elevating the orbit; and atmospheric drag is negligible, giving GSOs lifetimes of thousands of years. [35]

The retirement process is becoming increasingly regulated and satellites must have a 90% chance of moving over 200 km above the geostationary belt at end of life. [36]

Space debris

Space debris in geosynchronous orbits typically has a lower collision speed than at LEO since most GSO satellites orbit in the same plane, altitude and speed; however, the presence of satellites in eccentric orbits allows for collisions at up to 4 km/s. Although a collision is comparatively unlikely, GSO satellites have a limited ability to avoid any debris. [37]

Debris less than 10 cm in diameter cannot be seen from the Earth, making it difficult to assess their prevalence. [38]

Despite efforts to reduce risk, spacecraft collisions have occurred. The European Space Agency telecom satellite Olympus-1 was struck by a meteoroid on August 11, 1993, and eventually moved to a graveyard orbit, [39] and in 2006 the Russian Express-AM11 communications satellite was struck by an unknown object and rendered inoperable, [40] although its engineers had enough contact time with the satellite to send it into a graveyard orbit. In 2017 both AMC-9 and Telkom-1 broke apart from an unknown cause. [41] [38] [42]

Properties

The orbit of a geosynchronous satellite at an inclination, from the perspective of an off-Earth observer (ECI) and of an observer rotating around the Earth at its spin rate (ECEF). Geosynchronous no geostationary orbit.gif
The orbit of a geosynchronous satellite at an inclination, from the perspective of an off-Earth observer (ECI) and of an observer rotating around the Earth at its spin rate (ECEF).

A geosynchronous orbit has the following properties:

Period

All geosynchronous orbits have an orbital period equal to exactly one sidereal day. [43] This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties. [44] [21] :121 This orbital period, T, is directly related to the semi-major axis of the orbit through the formula:

where:

a is the length of the orbit's semi-major axis
is the standard gravitational parameter of the central body [21] :137

Inclination

A geosynchronous orbit can have any inclination.

Satellites commonly have an inclination of zero, ensuring that the orbit remains over the equator at all times, making it stationary with respect to latitude from the point of view of a ground observer (and in the ECEF reference frame). [21] :122

Another popular inclinations is 63.4° for a Tundra orbit, which ensures that the orbit's argument of perigee does not change over time. [23]

Ground track

In the special case of a geostationary orbit, the ground track of a satellite is a single point on the equator. In the general case of a geosynchronous orbit with a non-zero inclination or eccentricity, the ground track is a more or less distorted figure-eight, returning to the same places once per sidereal day. [21] :122

See also

Related Research Articles

<span class="mw-page-title-main">Geostationary orbit</span> Circular orbit above Earths Equator and following the direction of Earths rotation

A geostationary orbit, also referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) in altitude above Earth's equator, 42,164 km (26,199 mi) in radius from Earth's center, and following the direction of Earth's rotation.

<span class="mw-page-title-main">Communications satellite</span> Artificial satellite that relays radio signals

A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently.

<span class="mw-page-title-main">Low Earth orbit</span> Orbit around Earth between 160 and 2000 km

A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi), while the farthest in LEO, before medium Earth orbit (MEO), have an altitude more than about one-third of the radius of Earth, roughly at the beginning of the inner Van Allen radiation belt.

Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by the Space and Communications division of Hughes Aircraft Company. Syncom 2, launched in 1963, was the world's first geosynchronous communications satellite. Syncom 3, launched in 1964, was the world's first geostationary satellite.

<span class="mw-page-title-main">Geostationary transfer orbit</span> Transfer orbit used to reach geosynchronous or geostationary orbit

In space mission design, a geostationary transfer orbit (GTO) or geosynchronous transfer orbit is a highly elliptical type of geocentric orbit, usually with a perigee as low as low Earth orbit (LEO) and an apogee as high as geostationary orbit (GEO). Satellites that are destined for geosynchronous orbit (GSO) or GEO are often put into a GTO as an intermediate step for reaching their final orbit. Manufacturers of launch vehicles often advertise the amount of payload the vehicle can put into GTO.

A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere. map

<span class="mw-page-title-main">Molniya (satellite)</span> Soviet military surveillance and communications satellites

The Molniya series satellites were military and communications satellites launched by the Soviet Union from 1965 to 1991, and by the Russian Federation from 1991 to 2004. These satellites used highly eccentric elliptical orbits known as Molniya orbits, which have a long dwell time over high latitudes. They are suited for communications purposes in polar regions, in the same way that geostationary satellites are used for equatorial regions.

<span class="mw-page-title-main">Molniya orbit</span> Type of high-latitude satellite orbit

A Molniya orbit is a type of satellite orbit designed to provide communications and remote sensing coverage over high latitudes. It is a highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of 270 degrees, and an orbital period of approximately half a sidereal day. The name comes from the Molniya satellites, a series of Soviet/Russian civilian and military communications satellites which have used this type of orbit since the mid-1960s. A variation on the Molniya orbit is the so-called Three Apogee (TAP) orbit, whose period is a third of a sidereal day.

In astrodynamics, orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft or celestial body. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its target. For many low Earth orbit satellites, the effects of non-Keplerian forces, i.e. the deviations of the gravitational force of the Earth from that of a homogeneous sphere, gravitational forces from Sun/Moon, solar radiation pressure and air drag, must be counteracted.

<span class="mw-page-title-main">Tundra orbit</span> Highly elliptical and highly inclined synchronous orbit

A Tundra orbit is a highly elliptical geosynchronous orbit with a high inclination, an orbital period of one sidereal day, and a typical eccentricity between 0.2 and 0.3. A satellite placed in this orbit spends most of its time over a chosen area of the Earth, a phenomenon known as apogee dwell, which makes them particularly well suited for communications satellites serving high-latitude regions. The ground track of a satellite in a Tundra orbit is a closed figure 8 with a smaller loop over either the northern or southern hemisphere. This differentiates them from Molniya orbits designed to service high-latitude regions, which have the same inclination but half the period and do not loiter over a single region.

<span class="mw-page-title-main">Medium Earth orbit</span> Earth-centered orbit above low Earth orbit and below geostationary orbit

A medium Earth orbit (MEO) is an Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between 2,000 and 35,786 km above sea level.

A near-equatorial orbit is an orbit that lies close to the equatorial plane of the object orbited. Such an orbit has an inclination near 0°. On Earth, such orbits lie on the celestial equator, the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. A geostationary orbit is a particular type of equatorial orbit, one which is geosynchronous. A satellite in a geostationary orbit appears stationary, always at the same point in the sky, to observers on the surface of the Earth.

<span class="mw-page-title-main">Ground track</span> Path on the surface of the Earth or another body directly below an aircraft or satellite

A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track or subsatellite track, and is the vertical projection of the satellite's orbit onto the surface of the Earth.

<span class="mw-page-title-main">Geosynchronous satellite</span> Satellite with an orbital period equal to Earths rotation period

A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of analemma. A special case of geosynchronous satellite is the geostationary satellite, which has a geostationary orbit – a circular geosynchronous orbit directly above the Earth's equator. Another type of geosynchronous orbit used by satellites is the Tundra elliptical orbit.

Spacecraft collision avoidance is the implementation and study of processes minimizing the chance of orbiting spacecraft inadvertently colliding with other orbiting objects. The most common subject of spacecraft collision avoidance research and development is for human-made satellites in geocentric orbits. The subject includes procedures designed to prevent the accumulation of space debris in orbit, analytical methods for predicting likely collisions, and avoidance procedures to maneuver offending spacecraft away from danger.

Orion 3 was an American spacecraft which was intended for use by Orion Network Systems, as a geostationary communications satellite. It was to have been positioned in geostationary orbit at a longitude of 139° East, from where it was to have provided communications services to Asia and Oceania. Due to a malfunction during launch, it was instead delivered to a useless low Earth orbit.

<span class="mw-page-title-main">Telstar</span> Name of various communications satellites

Telstar is the name of various communications satellites. The first two Telstar satellites were experimental and nearly identical. Telstar 1 launched on top of a Thor-Delta rocket on July 10, 1962. It successfully relayed through space the first television pictures, telephone calls, and telegraph images, and provided the first live transatlantic television feed. Telstar 2 was launched May 7, 1963. Telstar 1 and 2—though no longer functional—still orbit the Earth.

<span class="mw-page-title-main">Inmarsat-4A F4</span> Geostationary communications satellite

Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 satellite operated by United Kingdom-based Inmarsat in partnership with the European Space Agency. Launched in 2013, it is used to provide mobile communications to Africa and parts of Europe and Asia.

References

  1. 1 2 3 4 Howell, Elizabeth. "What Is a Geosynchronous Orbit?". Space.com. Retrieved July 15, 2022.
  2. Noordung, Hermann (1929). Das Problem der Befahrung des Weltraums: Der Raketen-Motor (PDF). Berlin: Richard Carl Schmidt & Co. pp. 98–100.
  3. "(Korvus's message is sent) to a small, squat building at the outskirts of Northern Landing. It was hurled at the sky. ... It ... arrived at the relay station tired and worn, ... when it reached a space station only five hundred miles above the city of North Landing." Smith, George O. (1976). The Complete Venus Equilateral. New York: Ballantine Books. pp. 3–4. ISBN   978-0-345-28953-7.
  4. "It is therefore quite possible that these stories influenced me subconsciously when ... I worked out the principles of synchronous communications satellites ...", McAleer, Neil (1992). Arthur C. Clarke. Contemporary Books. p. 54. ISBN   978-0-809-24324-2.
  5. 1 2 Clarke, Arthur C. (October 1945). "Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage?" (PDF). Wireless World . pp. 305–308. Archived from the original (PDF) on March 18, 2009. Retrieved March 4, 2009.
  6. Phillips Davis (ed.). "Basics of Space Flight Section 1 Part 5, Geostationary Orbits". NASA . Retrieved August 25, 2019.
  7. Mills, Mike (August 3, 1997). "Orbit Wars: Arthur C. Clarke and the Global Communications Satellite". The Washington Post Magazine. pp. 12–13. Retrieved August 25, 2019.
  8. Kidder, S.Q. (2015). "Satellites and satellite remote senssing:[ vague ] --> Orbits". In North, Gerald; Pyla, John; Zhang, Fuqing (eds.). Encyclopedia of Atmospheric Sciences (2 ed.). Elsiver. pp. 95–106. doi:10.1016/B978-0-12-382225-3.00362-5. ISBN   978-0-12-382225-3.
  9. Brown, C.D. (1998). Spacecraft Mission Design (2nd ed.). AIAA Education Series. p. 81. ISBN   978-1-60086-115-4.
  10. "Ariane 5 User's Manual Issue 5 Revision 1" (PDF). Ariane Space. July 2011. Archived from the original (PDF) on October 4, 2013. Retrieved July 28, 2013.
  11. "What is orbit?". NASA. October 25, 2001. Archived from the original on April 6, 2013. Retrieved March 10, 2013. Satellites that seem to be attached to some location on Earth are in Geosynchronous Earth Orbit (GEO)...Satellites headed for GEO first go to an elliptical orbit with an apogee about 23,000 miles. Firing the rocket engines at apogee then makes the orbit round. Geosynchronous orbits are also called geostationary.
  12. 1 2 3 4 McClintock, Jack (November 9, 2003). "Communications: Harold Rosen – The Seer of Geostationary Satellites". Discover Magazine. Retrieved August 25, 2019.
  13. Perkins, Robert (January 31, 2017). Harold Rosen, 1926–2017. Caltech. Retrieved August 25, 2019.
  14. 1 2 3 Vartabedian, Ralph (July 26, 2013). "How a satellite called Syncom changed the world". Los Angeles Times . Retrieved August 25, 2019.
  15. Glover, Daniel R. (1997). "Chapter 6: NASA Experimental Communications Satellites, 1958-1995". In Andrew J Butrica (ed.). Beyond The Ionosphere: Fifty Years of Satellite Communication. NASA. Bibcode:1997bify.book.....B.
  16. David R. Williams (ed.). "Syncom 2". NASA. Retrieved September 29, 2019.
  17. "World's First Geosynchronous Satellite Launched". History Channel. Foxtel. June 19, 2016. Archived from the original on December 7, 2019. Retrieved August 25, 2019.
  18. "ITU releases 2018 global and regional ICT estimates". International Telecommunication Union. December 7, 2018. Retrieved August 25, 2019.
  19. Thompson, Geoff (April 24, 2019). "Australia was promised superfast broadband with the NBN. This is what we got". ABC . Retrieved August 25, 2019.
  20. Tibken, Shara (October 22, 2018). "In farm country, forget broadband. You might not have internet at all. 5G is around the corner, yet pockets of America still can't get basic internet access". CNET . Retrieved August 25, 2019.
  21. 1 2 3 4 5 6 7 8 9 10 11 Wertz, James Richard; Larson, Wiley J. (1999). Larson, Wiley J.; Wertz, James R. (eds.). Space Mission Analysis and Design. Microcosm Press and Kluwer Academic Publishers. Bibcode:1999smad.book.....W. ISBN   978-1-881883-10-4.
  22. "Orbits". ESA. October 4, 2018. Retrieved October 1, 2019.
  23. 1 2 Maral, Gerard; Bousquet, Michel (August 24, 2011). "2.2.1.2 Tundra Orbits". Satellite Communications Systems: Systems, Techniques and Technology. John Wiley & Sons. ISBN   978-1-119-96509-1.
  24. Jenkin, A.B.; McVey, J.P.; Wilson, J.R.; Sorge, M.E. (2017). Tundra Disposal Orbit Study. 7th European Conference on Space Debris. ESA Space Debris Office. Archived from the original on October 2, 2017. Retrieved October 2, 2017.
  25. "Sirius Rising: Proton-M Ready to Launch Digital Radio Satellite Into Orbit". AmericaSpace. October 18, 2013. Archived from the original on June 28, 2017. Retrieved July 8, 2017.
  26. Japan Aerospace Exploration Agency (July 14, 2016), Interface Specifications for QZSS, version 1.7, pp. 7–8, archived from the original on April 6, 2013
  27. "Quasi-Zenith Satellite Orbit (QZO)". Archived from the original on March 9, 2018. Retrieved March 10, 2018.
  28. 1 2 Farber, Nicholas; Aresini, Andrea; Wauthier, Pascal; Francken, Philippe (September 2007). A general approach to the geostationary transfer orbit mission recovery. 20th International Symposium on Space Flight Dynamics. p. 2.
  29. "Launching Satellites". EUMETSAT . Archived from the original on December 21, 2019. Retrieved January 26, 2020.
  30. Davis, Jason (January 17, 2014). "How to get a satellite to geostationary orbit". The Planetary Society. Retrieved October 2, 2019.
  31. "Repositioning geostationary satellites". Satellite Signals. February 22, 2022. Archived from the original on November 27, 2022. Retrieved May 23, 2023.
  32. 1 2 USpatent 5183225,Forward, Robert,"Statite: Spacecraft That Utilizes Sight Pressure and Method of Use",published February 2, 1993
  33. "Science: Polar 'satellite' could revolutionise communications". New Scientist. No. 1759. March 9, 1991. Retrieved October 2, 2019.
  34. Edwards, Bradley C. (March 1, 2003). "The Space Elevator NIAC Phase II Final Report" (PDF). NASA Institute for Advanced Concepts. p. 26. Archived (PDF) from the original on October 9, 2022.
  35. "Frequently Asked Questions: Orbital Debris". NASA. September 2, 2011. Archived from the original on March 23, 2020. Retrieved February 9, 2020.
  36. EUMETSAT (April 3, 2017). "Where old satellites go to die". phys.org.
  37. Stephens, Marric (December 12, 2017). "Space debris threat to geosynchronous satellites has been drastically underestimated". Physics World.
  38. 1 2 Henry, Caleb (August 30, 2017). "ExoAnalytic video shows Telkom-1 satellite erupting debris". SpaceNews.com.
  39. "N° 40–1993: OLYMPUS: End of mission" (Press release). ESA. August 26, 1993. 40–1993. Archived from the original on October 31, 2022. Retrieved May 23, 2023.
  40. "Notification for Express-AM11 satellite users in connection with the spacecraft failure". Russian Satellite Communications Company. April 19, 2006 via Spaceref.[ permanent dead link ]
  41. Dunstan, James E. (January 30, 2018). "Do we care about orbital debris at all?". SpaceNews.com.
  42. "AMC 9 Satellite Anomaly associated with Energetic Event & sudden Orbit Change – Spaceflight101". spaceflight101.com. June 20, 2017. Archived from the original on December 26, 2019. Retrieved January 27, 2020.
  43. Chobotov, Vladimir, ed. (1996). Orbital Mechanics (2nd ed.). Washington, DC: AIAA Education Series. p. 304. ISBN   9781563471797. OCLC   807084516.
  44. Vallado, David A. (2007). Fundamentals of Astrodynamics and Applications. Hawthorne, CA: Microcosm Press. p. 31. OCLC   263448232.