Subsynchronous orbit

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A subsynchronous orbit is an orbit of a satellite that is nearer the planet than it would be if it were in synchronous orbit, i.e. the orbital period is less than the sidereal day of the planet. [1]

Orbit gravitationally curved path of an object around a point in outer space; circular or elliptical path of one object around another object

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the central mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.

Satellite Human-made object put into an orbit around the earth or other planet

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon.

A synchronous orbit is an orbit in which an orbiting body has a period equal to the average rotational period of the body being orbited, and in the same direction of rotation as that body.


Technical considerations

An Earth satellite that is in (a prograde) subsynchronous orbit will appear to drift eastward as seen from the Earth's surface. [1]

Economic importance in commercial spaceflight

The Geosynchronous-belt subsynchronous orbital regime is regularly used in spaceflight. This orbit is typically used to house working communication satellites that have not yet been deactivated, and may be still be used again in geostationary service if the need arises. [2]

Geosynchronous orbit satellite orbit keeping the satellite at a fixed longitude above the equator

A geosynchronous orbit is an orbit around Earth of a satellite with an orbital period that matches Earth's rotation on its axis, which takes 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 traces out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity. Satellites are typically launched in an eastward direction. A geosynchronous orbit is 35,786 km (22,236 mi) above the Earth's surface. Those closer to Earth orbit faster than Earth rotates, so from Earth, they appear to move eastward while those that orbit beyond geosynchronous distances appear to move westward.

Spaceflight essentially an extreme form of ballistic flight,use of space technology to achieve the flight of spacecraft into and through outer space, used in space exploration, and also in commercial activities like space tourism and satellite telecommunications

Spaceflight is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.

Geostationary orbit circular orbit above the Earths equator and following the direction of the Earths rotation

A geostationary orbit, often referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) above Earth's equator and following the direction of Earth's rotation. An object in such an orbit appears motionless, at a fixed position in the sky, to ground observers. Communications satellites and weather satellites are often placed in geostationary orbits, so that the satellite antennae that communicate with them do not have to rotate to track them, but can be pointed permanently at the position in the sky where the satellites are located. Using this characteristic, ocean-color monitoring satellites with visible and near-infrared light sensors can also be operated in geostationary orbit in order to monitor sensitive changes of ocean environments.

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Related Research Articles

Space technology is technology developed by space science or the aerospace industry for use in spaceflight, satellites, or space exploration. Space technology includes spacecraft, satellites, space stations, and support infrastructure, equipment, and procedures. Space is such a novel environment that attempting to work in it requires new tools and techniques. Many common everyday services such as weather forecasting, remote sensing, GPS systems, satellite television, and some long distance communications systems critically rely on space infrastructure. Of the sciences, astronomy and Earth science benefit from space technology. New technologies originating with or accelerated by space-related endeavours are often subsequently exploited in other economic activities.

Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by Hughes Space and Communications. 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.

Geostationary transfer orbit Hohmann transfer orbit used to reach geosynchronous or geostationary orbit

A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a Hohmann transfer orbit—an elliptical orbit used to transfer between two circular orbits of different radii in the same plane—used to reach geosynchronous or geostationary orbit using high-thrust chemical engines.

A satellite is said to occupy an inclined orbit around Earth if the orbit exhibits an angle other than 0° to the equatorial plane. This angle is called the orbit's inclination. A planet is said to have an inclined orbit around the Sun if it has an angle other than 0° to the ecliptic plane.

A geocentric orbit or Earth orbit involves any object orbiting Planet Earth, such as the Moon or artificial satellites. In 1997 NASA estimated there were approximately 2,465 artificial satellite payloads orbiting the Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earth's atmosphere.

Sun-synchronous orbit type of geocentric orbit

A Sun-synchronous orbit is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is an orbit arranged so that it precesses through one complete revolution each year, so it always maintains the same relationship with the Sun.

PAS-22, previously known as AsiaSat 3 and then HGS-1, was a geosynchronous communications satellite, which was salvaged from an unusable geosynchronous transfer orbit by means of the Moon's gravity.

GSAT-1 was an experimental communications satellite launched aboard the maiden flight of the GSLV rocket. The spacecraft was equipped with instrumentation to test Pulse-code modulation (PCM) transmitting on S-band frequencies and transponders operating in the C-band. The spacecraft was unable to complete its mission after a launch failure left it in a lower than planned orbit and propulsion issues prevented the satellite from correcting this via its own maneuvering system.

An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.


Fēngyún, abbreviated FY, are China's weather satellites. China has launched polar orbit and geosynchronous orbit meteorological satellites since 1988. On January 11, 2007 China destroyed one of these satellites (FY-1C) in a test of an anti-satellite missile.

A supersynchronous orbit is either an orbit with a period greater than that of a synchronous orbit, or just an orbit whose apoapsis is higher than that of a synchronous orbit. A synchronous orbit has a period equal to the rotational period of the body which contains the barycenter of the orbit.

Medium Earth orbit Earth-centered orbit above low Earth orbit and below geostationary orbit

Medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), is the region of space around Earth above low Earth orbit and below geosynchronous orbit.

Geosynchronous satellite satellite in geosynchronous orbit

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.


GOES 2, known as GOES-B before becoming operational, was a geostationary weather satellite which was operated by the United States National Oceanic and Atmospheric Administration as part of the Geostationary Operational Environmental Satellite system. GOES 2 was built by Ford Aerospace, and was based on the satellite bus developed for the Synchronous Meteorological Satellite programme. At launch it had a mass of 295 kilograms (650 lb). It was positioned in geostationary orbit, from where it was used for weather forecasting in the United States. Following its retirement as a weather satellite, it was used as a communications satellite until its final decommissioning in 2001.


  1. 1 2 Maral, Gérard; Michel Bousquet; Zhili Sun (2009). Satellite communications systems : systems, techniques and technology. Wiley. OCLC   701718866.
  2. Kumar, Krishna (March 1993). "Geosynchronous satellites at sub-synchronous altitudes". Acta Astronautica. 29 (3): 149–151. Bibcode:1993AcAau..29..149K. doi:10.1016/0094-5765(93)90043-V . Retrieved 5 October 2013.