Geosynchronous satellite

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Satellites in geostationary orbit.

A geosynchronous satellite is a

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
.

Geostationary satellites have the unique property of remaining permanently fixed in exactly the

communication network
based on communication with or through geosynchronous satellites.

Definition

The term geosynchronous refers to the satellite's orbital period which enables it to be matched, with the rotation of the Earth ("geo-"). Along with this orbital period requirement, to be

geostationary
as well, the satellite must be placed in an orbit that puts it in the vicinity over the equator. These two requirements make the satellite appear in an unchanging area of visibility when viewed from the Earth's surface, enabling continuous operation from one point on the ground. The special case of a geostationary orbit is the most common type of orbit for communications satellites.

If a geosynchronous satellite's orbit is not exactly aligned with the Earth's equator, the orbit is known as an inclined orbit. It will appear (when viewed by someone on the ground) to oscillate daily around a fixed point. As the angle between the orbit and the equator decreases, the magnitude of this oscillation becomes smaller; when the orbit lies entirely over the equator in a circular orbit, the satellite remains stationary relative to the Earth's surface – it is said to be geostationary.

Application

Further information: List of satellites in geosynchronous orbit

As of October 2018, there are approximately 446 active geosynchronous satellites, some of which are not operational.[1][2][3]

A geostationary satellite is in orbit around the Earth at an altitude where it orbits at the same rate as the Earth turns. An observer at any place where the satellite is visible will always see it in exactly the same spot in the sky, unlike stars and planets that move continuously.

Geostationary satellites appear to be fixed over one spot above the equator. Receiving and transmitting

television broadcasting and weather forecasting, and have a number of important defense and intelligence
applications.

One disadvantage of geostationary satellites is a result of their high altitude:

packets
once it is known that earlier packets have been received. Slow start is very slow over a path using a geostationary satellite. RFC 2488, written in 1999, gives several suggestions on this issue.

There are some advantages of geo-stationary satellites:

  • Get high temporal resolution data.
  • Tracking of the satellite by its earth stations is simplified.
  • Satellite always in same position.

A disadvantage of geostationary satellites is the incomplete geographical coverage, since ground stations at higher than roughly 60 degrees latitude have difficulty reliably receiving signals at low elevations. Satellite dishes at such high latitudes would need to be pointed almost directly towards the horizon. The signals would have to pass through the largest amount of atmosphere, and could even be blocked by land topography, vegetation or buildings. In the USSR, a practical solution was developed for this problem with the creation of special Molniya / Orbita inclined path satellite networks with

Sirius Radio
satellites.

History

The concept was first proposed by

Wireless World in 1945.[4]
Working prior to the advent of solid-state electronics, Clarke envisioned a trio of large, crewed space stations arranged in a triangle around the planet. Modern satellites are numerous, uncrewed, and often no larger than an automobile.

Widely known as the "father of the geosynchronous satellite",

Delta rocket B booster from Cape Canaveral
July 26, 1963.

The first

Syncom 3, launched on August 19, 1964, with a Delta D launch vehicle from Cape Canaveral. The satellite, in orbit approximately above the International Date Line, was used to telecast the 1964 Summer Olympics
in Tokyo to the United States.

Westar 1 was America's first domestic and commercially launched geostationary communications satellite, launched by Western Union and NASA on April 13, 1974.

See also

References

  1. ^ Christy, Robert. "Geosynchronous Satellites - By Location". Archived from the original on 19 October 2013. Retrieved 18 October 2013.
  2. ^ "List of satellites in geostationary orbit". www.satsig.net. Retrieved 2018-12-10.
  3. ^ "CelesTrak: Current NORAD Two-Line Element Sets". www.celestrak.com. Retrieved 2018-12-10.
  4. ^ "Extra-Terrestrial Relays — Can Rocket Stations Give Worldwide Radio Coverage?" (PDF). Arthur C. Clark. October 1945. Archived from the original (PDF) on 2009-03-18. Retrieved 2009-03-04.
  5. ^ "Geosynchronous Satellite". Massachusetts Institute of Technology. Archived from the original on 2003-04-17.

External links

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