- Geostationary orbit The vehicle will be able to launch satellites of up to 750 kg into geostationary orbit.
- The geostationary orbit is a circular orbit directly above the Earth’s equator. How high above the Earth’s surface must the geostationary satellite be placed into orbit?
The geostationary orbit is a unique resource used by many satellites: its parameters must satisfy very precise conditions (circular orbit in the equatorial plane and at an altitude of 35,786 km) to have a fixed position in relation to the Earth. On the other hand, more and more operators want to place satellites on this orbit mainly for.
The geostationary orbit is a special case of the geosynchronous orbit, which is any orbit with a period equal to Earth’s rotation period. The concept for such an orbit was proposed in 1945 by British author and scientist Arthur C. Clarke in an article entitled “Extra-Terrestrial Relays” for Wireless World. A geosynchronous orbit is a high Earth orbit that allows satellites to match Earth's rotation. Located at 22,236 miles (35,786 kilometers) above Earth's equator, this position is a valuable spot.
Geostationary/geosynchronous csatellites have revolutionized global communications (phone, internet) and TV broadcasting.
A geostationary satellite is an earth-orbiting satellite, placed at an altitude of approximately 35,800 kilometers (22,300 miles) directly over the equator, that revolves in the same direction the earth rotates (west to east). At this altitude, one orbit takes 24 hours, the same length of time as the earth requires to rotate once on its axis. The term geostationary comes from the fact that such a satellite appears nearly stationary in the sky as seen by a ground-based observer.
Other Iridium Phones:
A single geostationary satellite is on a line of sight with about 40 percent of the earth's surface. Three such satellites, each separated by 120 degrees of longitude, can provide coverage of the entire planet, with the exception of small circular regions centered at the north and south geographic poles. A geostationary satellite can be accessed using a directional antenna, usually a small dish, aimed at the spot in the sky where the satellite appears to hover. The principal advantage of this type of satellite is the fact that an earthbound directional antenna can be aimed and then left in position without further adjustment. Another advantage is the fact that because highly directional antennas can be used, interference from surface-based sources, and from other satellites, is minimized.
Derivation of geostationary altitude
In any circular orbit, the centripetal acceleration required to maintain the orbit is provided by the gravitational force on the satellite. To calculate the geostationary orbit altitude, one begins with this equivalence, and uses the fact that the orbital period is one sidereal day.
By Newton's second law of motion, we can replace the forces F with the mass m of the object multiplied by the acceleration felt by the object due to that force:
We note that the mass of the satellite m appears on both sides — geostationary orbit is independent of the mass of the satellite. So calculating the altitude simplifies into calculating the point where the magnitudes of the centripetal acceleration required for orbital motion and the gravitational acceleration provided by Earth's gravity are equal.
The centripetal acceleration's magnitude is:
where ? is the angular speed, and r is the orbital radius as measured from the Earth's center of mass.
The magnitude of the gravitational acceleration is:
where M is the mass of Earth, 5.9736 × 1024 kg, and G is the gravitational constant, 6.67428 ± 0.00067 × 10-11 m3 kg-1 s-2.
Equating the two accelerations gives:
The product GM is known with much greater accuracy than either factor; it is known as the geocentric gravitational constant µ = 398,600.4418 ± 0.0008 km3 s-2:
The angular speed ? is found by dividing the angle travelled in one revolution (360° = 2p rad) by the orbital period (the time it takes to make one full revolution: one sidereal day, or 86,164.09054 seconds).[3] This gives:
The resulting orbital radius is 42,164 kilometres (26,199 mi). Subtracting the Earth's equatorial radius, 6,378 kilometres (3,963 mi), gives the altitude of 35,786 kilometres (22,236 mi). Orbital speed (how fast the satellite is moving through space) is calculated by multiplying the angular speed by the orbital radius:
Orbite alocation
Satellites in geostationary orbit must all occupy a single ring above the equator. The requirement to space these satellites apart means that there are a limited number of orbital 'slots' available, thus only a limited number of satellites can be placed in geostationary orbit. This has led to conflict between different countries wishing access to the same orbital slots (countries at the same longitude but differing latitudes). These disputes are addressed through the International Telecommunication Union's allocation mechanism.[5] Countries located at the Earth's equator have also asserted their legal claim to control the use of space above their territory.[6] Since the Clarke Orbit is about 265,000 km (165,000 mi) long, countries and territories in less-populated parts of the world have been allocated slots already, even though they aren't used, yet. The problem presently lies over densely-populated areas such as the Americas and Europe/Africa, and above the middles of the three equatorial oceans.
Orbit Inclination
If a geosynchronous satellite's orbit is not exactly aligned with the equator, the orbit is known as an inclined orbit. It will appear (when viewed by someone on the ground) to oscillate daily around a fixed point in the sky. As the angle between the orbit and the equator decreases, the magnitude of this oscillation becomes smaller; when the orbit lies entirely over the equator, the satellite remains stationary relative to the Earth's surface – it is said to be geostationary.
Impact on signals
Satellites in geostationary orbits are far enough away from Earth that communication latency becomes very high — about a quarter of a second for a one-way trip from a ground based transmitter to a geostationary satellite and back, and close to half a second for round-trip end-to-end communication.
For example, for ground stations at latitudes of f=±45° on the same meridian as the satellite, the one-way delay can be computed by using the cosine rule, given the above derived geostationary orbital radius r, the Earth's radius R and the speed of light c, as
This presents problems for latency-sensitive applications such as voice communication or online gaming.
Application
There are approximately 300 operational geosynchronous satellites. Geostationary satellites appear to be fixed over one spot above the equator. Receiving and transmitting antennas on the earth do not need to track such a satellite. These antennas can be fixed in place and are much less expensive than tracking antennas. These satellites have revolutionized global communications, television broadcasting and weather forecasting, and have a number of important defense and intelligence applications.
One disadvantage of geostationary satellites is a result of their high altitude: radio signals take approximately 0.25 of a second to reach and return from the satellite, resulting in a small but significant signal delay. This delay increases the difficulty of telephone conversation and reduces the performance of common network protocols such as TCP/IP, but does not present a problem with non-interactive systems such as television broadcasts. There are a number of proprietary satellite data protocols that are designed to proxy TCP/IP connections over long-delay satellite links -- these are marketed as being a partial solution to the poor performance of native TCP over satellite links. TCP presumes that all loss is due to congestion, not errors, and probes link capacity with its 'slow-start' algorithm, which only sends packets once it is known that earlier packets have been received. Slow start is very slow over a path using a geostationary satellite.
Another disadvantage of geostationary satellites is the incomplete geographical coverage, since ground stations at higher than roughly 60 degrees latitude have difficulty reliably receiving signals at low elevations. Satellite dishes in the Northern Hemisphere would need to be pointed almost directly towards the horizon. The signals would have to pass through the largest amount of atmosphere, and could even be blocked by land topography, vegetation or buildings. In the USSR, a practical solution was developed for this problem with the creation of special Molniya / Orbita inclined path satellite networks with elliptical orbits. Similar elliptical orbits are used for the Sirius Radio satellites.
Geostationary satellites have two major limitations. First, because the orbital zone is an extremely narrow ring in the plane of the equator, the number of satellites that can be maintained in geostationary orbits without mutual conflict (or even collision) is limited. Second, the distance that an electromagnetic (EM) signal must travel to and from a geostationary satellite is a minimum of 71,600 kilometers or 44,600 miles. Thus, a latency of at least 240 milliseconds is introduced when an EM signal, traveling at 300,000 kilometers per second (186,000 miles per second), makes a round trip from the surface to the satellite and back.
There are two other, less serious, problems with geostationary satellites. First, the exact position of a geostationary satellite, relative to the surface, varies slightly over the course of each 24-hour period because of gravitational interaction among the satellite, the earth, the sun, the moon, and the non-terrestrial planets. As observed from the surface, the satellite wanders within a rectangular region in the sky called the box. The box is small, but it limits the sharpness of the directional pattern, and therefore the power gain, that earth-based antennas can be designed to have. Second, there is a dramatic increase in background EM noise when the satellite comes near the sun as observed from a receiving station on the surface, because the sun is a powerful source of EM energy. This effect, known as solar fade, is a problem only within a few days of the equinoxes in late March and late September. Even then, episodes last for only a few minutes and take place only once a day.
To celebrate Earth Day, we are sharing stunning views of our beautiful planet, captured by NOAA satellites.
Since 1970, NOAA satellites have been monitoring Earth’s weather, environment, oceans, and climate. They provide critical information that feeds forecasts and warns us of severe weather and environmental hazards. NOAA operates two primary types of satellites: geostationary and polar-orbiting.
Geostationary satellites orbit 22,236 miles above the equator at speeds equal to Earth’s rotation. This means they continuously view the same area. Because they stay above a fixed spot on the surface, they provide constant vigil to identify and track severe weather conditions and environmental hazards. Information from geostationary satellites is used for short-term (1-2 day) forecasts and also for tracking storm systems in real-time.
The Geostationary Operational Environmental Satellites – R Series (GOES-R) is NOAA’s newest generation of geostationary satellites. GOES-16, in operations as GOES East, keeps watch over most of North America, including the contiguous United States and Mexico, as well as Central and South America, the Caribbean, and the Atlantic Ocean to the west coast of Africa. GOES-17, which serves as GOES-West, watches over the western continental United States, Alaska, Hawaii, and the Pacific Ocean to New Zealand.
GOES-16 and GOES-17 each carry an imager and a lightning mapper that provide critical data about Earth’s weather and environment.
Polar-orbiting satellites circle the globe from the North Pole to the South Pole 14 times a day. They image the entire Earth at least twice daily, from 512 miles above its surface. Earth rotates counterclockwise underneath the path of the satellites, resulting in a different view with each orbit.
Global data from polar-orbiting satellites, including atmospheric temperature and moisture profiles, are used in numerical weather models to generate weather forecasts up to seven days out. Polar-orbiting satellites observe the whole world in higher resolution than GOES satellites, allowing for a broader and more detailed view of weather patterns and environmental conditions.
NOAA’s polar-orbiting satellites, the Joint Polar Satellite System’s (JPSS) NOAA-20 and NOAA/NASA Suomi-NPP, carry instruments not available on GOES, including a microwave sounding instrument, which allows scientists to see through clouds to what lies beneath. The polar satellites also carry the Day-Night Band, which enables scientists and forecasters to see cloud patterns at night, thanks to reflected moonlight.
Each of the geostationary and polar-orbiting satellites carries an advanced imager for providing detailed images of Earth. The imagers have many “channels,” each designed to detect specific features, such as cloud type, atmospheric water vapor, ozone, carbon dioxide, or areas of ice or snow. Combining data from multiple channels provides even more information for forecasters.
NOAA also operates additional satellites in low-Earth orbit and a deep space satellite at Lagrange point 1, approximately one million miles away from Earth. On board NOAA’s DSCOVR satellite is NASA’s Earth Polychromatic Imaging Camera (EPIC) instrument that watches Earth.
Different vantage points, geographic coverage, instrumentation, and imaging frequency from NOAA satellites offer unique information about our home planet. Together, they provide complementary measurements for a complete picture of what’s happening on Earth.
Geostationary Orbit Ksp
NOAA satellites see it all—hurricanes, severe thunderstorms, lightning, fires, dust storms, air quality, fog, volcanic eruptions, vegetation, snow and ice cover, flooding, sea and land surface temperature, ocean health and more. They can even track ship traffic and power outages. Every day, NOAA satellites provide critical information to keep us informed and help us stay safe. At NOAA, each day is Earth Day.