Geosynchronous
orbit.
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Geosynchronous and Geostationary
Orbit
A geosynchronous orbit may be defined as one with an orbital
period (the time needed to orbit once around the Earth) that matches
the rotation rate of the Earth. This is a sidereal day, which
is 23 hours 56 minutes and 4 seconds in length, and represents the
time taken for the Earth to rotate once about its polar axis relative
to a distant fixed point. This is about four minutes shorter than
the common day length of 24 hours, which is relative to the sun.
A geostationary orbit is a special case of a geosynchronous
orbit. A satellite is in a geostationary orbit when it appears stationary
from the point of view of an observer on the Earth's surface. This
can only occur when:
Thus, a geosynchronous satellite will be geostationary only with
the additional restrictions of it being in a circular orbit situated
over the equator.
The following parameters are always true for any geostationary
satellite:
Parameter
|
Value
|
Height above equator
|
35,785 km (22,236 miles)
|
Orbit radius
|
42,155 km (26,194 miles)
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Orbit circumference
|
264,869 km (164,582 miles)
|
Arc length per degree
|
736 km (457 miles)
|
Orbital velocity
|
11,066 km/hr= 3.07 km/sec (6,876 miles/hr)
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Source: Eumetstat |