New! Sign up for our free email newsletter.
Reference Terms
from Wikipedia, the free encyclopedia

Geosynchronous orbit

A geosynchronous orbit is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. It has a semi-major axis of 42,164 km (26,200 miles). In the special case of the geostationary orbit, an observer on the ground would not perceive the satellite as moving and would see it as a fixed point in the sky. Such orbits are useful for telecommunications relays. In the more general case, when the orbit has some inclination and/or eccentricity, the satellite would appear to describe a more or less distorted figure-eight in the sky, and would rest above the same spots of the Earth's surface once per sidereal day.

Synchronous orbits exist around all moons, planets, stars and black holes —unless they rotate so slowly that the orbit would be outside their Hill sphere. Most inner moons of planets have synchronous rotation, so their synchronous orbits are, in practice, limited to their leading and trailing Lagrange points. Objects with chaotic rotations (such as Hyperion) are also problematic, as their synchronous orbits keep changing unpredictably. If a geosynchronous orbit is circular and equatorial then it is also a geostationary orbit, and will maintain 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 one would see the Sun, Moon, and stars traverse the heavens behind it.

Related Stories
 


Space & Time News

August 1, 2025

Engineers at the University of Wisconsin-Madison uncovered a critical flaw in how lunar and Martian rovers are tested on Earth. Simulations revealed that test results have been misleading for decades because researchers only adjusted rover weight to ...
UF engineers, backed by DARPA and NASA, are perfecting laser-forming techniques that let metal sheets fold themselves into giant solar arrays, antennas, and even space-station parts right in ...
The LSST camera at the Vera C. Rubin Observatory has released its jaw-dropping first images, each capturing 45 times the area of the full moon in one shot. Over the next ten years, this cosmic giant will scan the southern sky in ultra-HD, helping ...
Imagine printing your Martian home from dust, sunlight, and a bit of biology. A new synthetic lichen system uses fungi and bacteria to grow building materials directly from Martian soil, completely autonomously and without human ...
Lichen from the Mojave Desert has stunned scientists by surviving months of lethal UVC radiation, suggesting life could exist on distant planets orbiting volatile stars. The secret? A microscopic “sunscreen” layer that protects their vital ...
AI has helped astronomers crack open some of the universe s best-kept secrets by analyzing massive datasets about black holes. Using over 12 million simulations powered by high-throughput computing, scientists discovered that the Milky Way's central ...
By using a clever quantum approach that involves two "hands" on a clock one moving quickly and invisibly in the quantum world, the other more traditionally scientists have found a way to boost timekeeping precision dramatically. Even better, this ...
Supermassive black holes might naturally replicate the colossal energies of man-made particle colliders possibly even revealing dark matter offering a cosmic shortcut to discoveries that would ...
Astronomers have revealed new research showing that millions of new solar system objects are likely to be detected by a brand-new facility, which is expected to come online later this ...
Scientists have identified a new source of energetic particles near the Sun. These definitive observations were made by instruments aboard NASA's Parker Solar Probe, which detected the powerful phenomena as the spacecraft dipped in and out of the ...
WASP-121b may have been born in a frozen zone and later migrated into its current inferno-like orbit. A surprise discovery of methane in the wrong place suggests intense vertical winds are reshaping how we understand planetary ...
Researchers have engineered a laser device smaller than a penny that they say could power everything from the LiDAR systems used in self-driving vehicles to gravitational wave detection, one of the most delicate experiments in existence to observe ...

Latest Headlines

updated 12:56 pm ET