A satellite high above the Earth can cover so much of Earth that the ESA says it only takes 3 equally-spaced satellites to cover the planet.Īnother advantage of a geosynchronous orbit is that aerials on Earth don't have to redirect or reposition to stay in touch with geosynchronous satellites that maintain the same position over Earth. The fact that geosynchronous allow satellites to maintain a set position over the globe makes them particularly useful for weather monitoring, allowing scientists to continuously observe a specific area to see how weather trends emerge and develop.Īn example of weather satellites around Earth in geosynchronous orbits are the National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite (GOES) system satellites GOES East (GOES-16) and GOES West (GOES-17).Īnother common use for geosynchronous orbits is communications. Geosynchronous orbits and geostationary orbits are prograde, which refers to a spacecraft moving in the same direction as the planet's motion as opposed to retrograde when a spacecraft moves opposite to the rotation What objects are in geosynchronous orbits In fact, NASA says that geostationary orbits are achieved by selecting a geosynchronous orbit that is perfectly circular described as having an eccentricity of 0 and an inclination of 0 right on the equator, or low enough that it can use propulsion to maintain its position over Earth. The key difference between a geostationary orbit and a geosynchronous orbit is while the latter can have any inclination, the former orbit sees satellites permanently 'parked' over the plane of Earth's equator. (Image credit: NASA/Robert Lea (created with Canva))Ī geostationary orbit is actually a type of geosynchronous orbit. Geosynchronous orbits vs geostationary orbitsĪ geostationary orbit is a type of geosynchronous orbit. In a geosynchronous orbit, to stay in sync with sidereal day and to avoid the downward pull of gravity the European Space Agency (ESA) says that satellites have to maintain a speed of around 7,000 miles per hour (11,300 kilometers per hour). This is because gravity follows an "inverse square law" and thus Earth's gravity is much weaker at high orbits. Lower orbits require greater speed to maintain their altitude. A satellite has to travel faster enough to "defeat" the downward pull of gravity. Like all satellites, those in geosynchronous orbits remain there because by performing a balancing act between Earth's gravitational influence and their velocity. At first engineers and scientists utilized low-Earth orbits believing it would take too much energy to get a satellite to a high-Earth geosynchronous orbit. ![]() There are three main types of orbit around Earth, low Earth orbits, medium-Earth orbits, and high-Earth orbits. This attitude is also much higher than other orbits meaning satellites in geosynchronous orbits are much further from Earth than those in other types of orbits making them the most distant satellites. This attitude has to be constant for a satellite to remain in sync with the Earth's sidereal day. Satellites are in geosynchronous orbits when they are located around 22,236 miles (35,786 kilometers), according to the European Space Agency (ESA). (Image credit: NOAA)Ī satellite in a geosynchronous orbit holds the same position over Earth by matching the duration of its orbit to what is called Earth's sidereal day, the time required for the Earth to rotate once relative to its background stars, which is 23 hours 56 minutes 4 seconds. This image of lightning over the Midwestern United States was captured on May 9, 2018, by the Geostationary Lightning Mapper instrument aboard the National Oceanic and Atmospheric Administration's GOES-17 satellite. Geosynchronous orbits are important for Earth-monitoring satellites.
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