Geostationary orbit
A geostationary orbit is a specific type of circular orbit around Earth, positioned approximately 35,786 kilometers (22,236 miles) above the equator. In this orbit, a satellite travels at the same rotational speed as the Earth, allowing it to appear stationary from the perspective of an observer on the ground. This synchronized motion is essential for various applications, particularly in communication technology, where satellites relay television, radio broadcasts, and data across the globe.
The concept of geostationary orbit emerged in the early 20th century, with theorists like Konstantin Tsiolkovsky and Arthur C. Clarke laying the groundwork for artificial satellites. Clarke’s innovative ideas in 1945 highlighted the feasibility of using multiple satellites positioned to cover the Earth, which ultimately led to the successful launches of geostationary satellites by NASA in the 1960s. Achieving this orbit requires meticulous calculations and precision in launching, as satellites must maintain their position over the equator and make adjustments, known as station keeping, to stay on course.
Today, geostationary satellites play a crucial role in global communications, enabling fast data transfer and connectivity, significantly impacting how people interact and share information worldwide.
Geostationary orbit
Geostationary orbit is an astronomical term relating to a special kind of orbit, or circular path, around a planet or other large body in space. An object in geostationary orbit, such as a satellite, travels at the exact speed at which the planet is rotating. The perfectly coordinated speeds make the orbiting object appear, from the perspective of an observer on the planet's surface, to be stationary in the sky.
Scientists and writers conceived the idea of a geostationary orbit in the early 1900s and developed the concept in the coming decades. By the 1960s, the National Aeronautics and Space Administration (NASA) began attempting to place artificial satellites in orbit. Since that time, many satellites have entered geostationary orbit above Earth. Today, these geostationary satellites are a crucial part of communication technology, relaying data such as television and radio broadcasts around the world.
Early Conceptualizations
For hundreds of years, scientists have studied orbits by watching the paths of natural satellites, such as the moons that circle some planets. Tracing these orbits led scientists to great discoveries about celestial mechanics, the ways in which bodies in space move around one another. By the early 1900s, these studies began to inspire science writers to theorize about artificial satellites that could travel around Earth. Scientists Konstantin Tsiolkovsky, Herman Potočnik , and Hermann Oberth wrote about the possibilities of placing human-made spacecraft into Earth's orbit. These writers even theorized about the exact altitude necessary for making the satellite objects travel in a geostationary manner.
In the early 1900s, people were just mastering the science of airplanes, and space travel would not become a possibility for several generations. Therefore, the early writers' theories were left in the realm of science fiction. However, the possibility of creating an artificial satellite reemerged in 1945, thanks to the writings of science author and theorist Arthur C. Clarke. By that year, rocket technology—largely based on the breakthroughs of German military scientists during World War II—had made travel to extremely high altitudes a distinct possibility.
Clarke's detailed plan, published in October 1945, set out the proposal that humans could use rocketry to launch several communication satellites into space. By bringing the satellites to a specific altitude, their orbit around Earth would perfectly match the pace at which Earth revolved, thus making the satellites geostationary. Clarke believed that launching three such satellites into orbit at equal intervals, as to form a triangle around the planet, would allow people to send radio broadcasts across the world. Radio stations could beam broadcasts to the nearest satellite, which could then transmit the signal to the other satellites and then back to any radio receiver on the planet, all within seconds. Clarke supported his revolutionary theory with exact calculations of distances, power requirements and sources, and radio frequencies. His contributions to satellite technology have led many scientists to refer to geostationary orbits as Clarke orbits.
Satellites in Geostationary Orbit
The theories of Clarke, like those of his predecessors, were still hampered by insufficient technology. Only by the 1960s did scientific advances make space travel and satellite communication feasible. In 1963, NASA undertook a project based on plans very similar to those set out by Clarke. This project, the Synchronous Communications Satellite program, or Syncom, began attempting to launch satellites into geostationary orbit.
The first Syncom satellite, launched in 1963, successfully reached Earth's orbit and began circling the planet. However, its path was geosynchronous, not geostationary—meaning the orbit was not perfectly matched with Earth's rotation. Later that year, NASA launched a second satellite into a similarly geosynchronous orbit, but the main goal of reaching a geostationary orbit still eluded the scientists. It was not until 1964 that a Syncom satellite reached the necessary altitude and made the needed directional adjustments to enter into a truly geostationary orbit. That launch marked the beginning of the age of geostationary satellites.
Scientists discovered that launching satellites required enormous precision. Rocket launches had to be performed with painstaking accuracy and carefully calculated speeds. Too much speed would hurl the satellite into outer space to be lost forever; not enough speed would fail to take the satellite into orbit, and it would crash back to the ground. Finding the perfect altitude for the satellite (ultimately determined to be about 22,237 miles above Earth) was one crucial key. Another key was making fine adjustments to the satellite's position to keep it from sliding into other orbits and losing its geostationary path. Satellites would have to travel precisely over the equator to maintain this special orbit. To accomplish this, scientists created small propulsion sources on satellites so they could correct and fine-tune their paths while traveling around Earth. The activity of path adjustment in orbit is called station keeping.
In the coming years, scientists perfected the system of launching satellites into geostationary orbits. Today, many such satellites have followed Earth's rotation. Much as Clarke theorized, these satellites have proven to be extremely effective in transferring information, bouncing radio and television broadcasts and other forms of data between users on the ground as well as cooperating satellites. This extensive network of satellites allows people to send information from one point on Earth to an almost unlimited range of other points in mere seconds. In modern times, much of the world's long-distance communication relies on satellite technology and the concept of the geostationary orbit.
Bibliography
"Basics of Space Flight: Planetary Orbits." NASA Jet Propulsion Laboratory. NASA. Web. 10 Dec. 2014. http://www2.jpl.nasa.gov/basics/bsf5-1.php
"Geostationary Orbit." The Planetary Society. The Planetary Society. Web. 10 Dec. 2014. http://www.planetary.org/multimedia/space-images/charts/geostationary-orbit.html
"How Do Satellites Work?: Geostationary Orbit." Federal Communications Commission (FCC) Satellite Learning Center. Federal Communications Commission. Web. 10 Dec. 2014. http://transition.fcc.gov/cgb/kidszone/satellite/kidz/geo.html
Kelso, T.S. "Basics of the Geostationary Orbit." CelesTrak/Satellite Times. CelesTrak. Web. 10 Dec. 2014. http://celestrak.com/columns/v04n07/