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A geostationary orbit is a circular orbit approximately 35,786 kilometers (22,236
miles) above Earth's equator, following the direction of Earth's rotation (see calculations
below). At this altitude, an object's orbital period matches Earth's rotational
period, causing it to remain fixed relative to a specific point on the surface.
This unique characteristic makes geostationary orbits invaluable for applications
like telecommunications, weather monitoring, and reconnaissance, as satellites in
this orbit provide continuous coverage over designated regions without requiring
tracking antennas on the ground.
The concept was first proposed by British science fiction writer and futurist
Arthur C. Clarke in a 1945 paper titled
Extra-Terrestrial Relays: Can Rocket Stations Give Worldwide Radio Coverage?,
published in Wireless World magazine. Clarke, who was then a Royal Air
Force radar specialist, mathematically demonstrated that an object placed at this
specific altitude would maintain a stationary position relative to Earth. He envisioned
a network of three such satellites spaced equally around the equator, which would
enable global communications coverage - a revolutionary idea at a time when rocketry
was still in its infancy and no human-made object had yet reached orbit.
Though it would take nearly two decades for technology to catch up to his vision,
with the launch of Syncom 3 in 1964 marking the first successful geostationary communications
satellite, Clarke's foresight earned him the title of the "father of the communications
satellite." The geostationary orbit is sometimes referred to as the "Clarke Orbit"
or "Clarke Belt" in his honor, a testament to how a single idea can shape the future
of global infrastructure.
Geosynchronous Earth Orbit Altitude Calculation
The altitude is derived by balancing the gravitational and centripetal forces
for an orbit that matches Earth's rotation. A geostationary orbit requires a period
(T) of one sidereal day, which is approximately 86,164 seconds.
The formula for the orbital radius (r) from Earth's center is:
r = 3√[(G * M * T2) / (4 * pi2)] where:
G is the gravitational constant (6.67430 x 10-11 m3 kg-1
s-2),
M is Earth's mass (5.972 x 1024 kg), and
T is
the orbital period (86164 s)
Calculating step by step:
First, compute T2 = 861642 ≈ 7.424 x 109 s2
Then, compute G * M = (6.67430 x 10-11) * (5.972 x 1024)
≈ 3.986 x 1014 m3 s-2
Multiply them: (3.986 x 1014) * (7.424 x 109) ≈ 2.958 x
1024 m3
Divide by 4 * pi2 (≈ 39.478): 2.958 x 1024 / 39.478 ≈ 7.496
x 1022 m3
Take the cube root: 3√(7.496 x 1022) ≈ 4.216 x 107
meters, or
Geosynchronous Orbit Altitude wrt Center of Earth: 4.216 x 107
meters, or 42,164 km, or 26,196 miles.
To find altitude above sea level, subtract Earth's average radius (6,378 km):
Geosynchronous Orbit Altitude wrt Mean Sea Level (MSL):
35,786 km, or 22,236 miles.
This calculation shows why all geostationary satellites must be at this specific
height above the equator, orbit in any angle relative to the equator or poles.
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