Monday, June 24, 2019
Earth Satellite Orbits
Whenever space and satellites are discussed, many classes are also discussed such as geostationary orbit, polar orbit. What are these classes? What are they required?
When you go to a theater to watch the drama, different seating shows you different aspects of the same stages, in the same way, different orbits of the Earth give the satellite the opportunity to inspect the earth from different perspectives. Each class has its own importance due to different reasons. In some classes, the satellite appears to be hinged at one point of the Earth, in some other classes, the satellite continues to travel continuously from many places on Earth.
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| Earth Satellite Orbits |
Originally there are three orbits of satellites on earth, high Earth orbit, medium earth orbit and low Earth orbit. Most of the weather satellites and some communications satellites live in high earth orbits, i.e. more than the surface of the Earth. There are satellite navigation and spy satellites living in Middle Earth orbit that are designed to monitor a particular area. Scientific satellites are in the lower class of the Earth, in which the fleet of international space station, NASA's Earth's inspection satellites is included.
The height of any orbit or the surface of the satellite determines the speed of the satellite from the distance of the satellite. Control of the motion of the satellite orbiting the Earth primarily has the force of the Earth's gravitational force. When the satellite is close to the Earth, the gravitational force is more stretch and thereby the speed of the satellite is high. NASA's Aqua satellite is at an altitude of 705 km above the surface of the Earth, and it takes a rotation of the Earth in 99 minutes, while a seasonal satellite takes 23 hours 56 minutes and 4 seconds to revolve the Earth from a height of 36,000 km. From 384,403 km from the center of the Earth, it takes 28 days to revolve the Earth.
Changing the height of any satellite also changes its orbital speed. This also creates a strange paradox. Suppose a satellite operator has to increase the orbital speed of the satellite, by not lighting up the satellite by burning satellite propellants. If he does this then the height of the satellite will increase and it will reduce the orbital speed of the satellite. To increase the speed of the satellite, the propellant rocket of the satellite must run in the reverse direction of the motion of the satellite, we can call it a braking on the surface of the Earth. This will bring the satellite closer to Earth in its class and its speed will increase.
In addition to height, eccentricity and orbital inclination also shape the orbit of the satellite. Classroom size is determined by decentralization. A satellite with less decentness keeps the class like a circle. The satellite with more decentness revolves around the orbit in the same way as an orbit, in this class the distance of the satellite from Earth changes continuously.
Orbital inclination is the angle between the orbit of the satellite and the equator between the Earth. The orbital inclination of the satellite that runs right above the equator is zero. If a satellite moves from the Earth's geographic north pole to the orbit of the southern pole, its orbital tilt will be 90 degrees.
The height, alignment and inclination of the satellite define the path of a satellite and the visible part of the Earth.
Three classes of satellite orbit
High Earth Orbit
When the satellite reaches a height of 42,164 km (36,000 km from the surface) from the Earth's center, it is at a point in which its orbital motion and the rotation speed of the Earth are the same. Now with the speed of the satellite and the rotation speed of the Earth being equal, the satellite appears to be stationary on the same longitude at the same longitude. It is possible that there is a deviation in north-south direction in satellite status. This particular class is called geosynchronous orbit.
If the geosynchronous orbital class is above the equator, i.e. its vicinity is zero and the orbital tilt is zero, then it is called geostationary orbit because it will be constant relative to any point in the earth. He will always be on the surface of the earth, at a point.
Geostationary class is very important for weather satellites because in this class, the satellite can continually observe on one part of the Earth. Whenever you see a picture of the Earth that gives information about the weather of your city on any website that provides weather information, then that image is a picture taken by a satellite or satellite satellite. Every few minutes, the weather like Satellites of the INSAT series of India sends information like clouds, water vapor, wind direction to the Earth's Weather Center, by analyzing this information, the weather is estimated.
Geospatial satellites are always on top of one location so that they are used for communication media (phones, TVs and radios). Geostationary Operational Environmental Satellite (GOES), operated by NASA, and the National Oceanic and Atmospheric Administration (NOAA), helps in the discovery, relief and rescue of aircraft and aircraft disaster Do it.
Many solar cells with high earth orbit also monitor. GOES satellites have equipment for monitoring space weather, which take pictures of the sun and keep checking the magnetic field and solar wind around them.
There is some more important point beyond the higher Earth orbit, which is called the Lagrange Point. At these points the gravity of the Sun and the Earth is the same. Any object or body located on these points orbits the Sun with the Earth, because it is tied equally by both the Earth and the Sun.
There are a total of five Lagrangs points, out of which two L4 and L5 points are either balanced or fixed. At the other three points, the satellite is like a ball on top of a mountain, with light irritation on these points, the satellite goes away from its place like a rolling ball from the hill. On these three points, the satellite has to be constantly adjusted to be stable, balanced. The satellites located on the last two points are like a ball in a bowl, for some reason, if they are removed from these points, they also come back to their actual position.
The first Lagrang's point is in between the Earth and the Sun, from which the Sun can be constantly monitored from this point. The NASA and Solar and Heliospheric Observatory (SOHO) of the European Space Institute (ESA) are located at this point 1.5 million kilometers away from the Earth.
The second Lagrange point is at such distance from the Earth but behind the Earth, the Earth is always between the Sun and the Second Lagrange point. In this situation, the Earth, the Sun and the satellite are in the same line, so that at this point the heat shield is required to keep the satellites at that point in order to avoid the sun and the heat of the Earth. This space is the best place for telescopes, in the future, the James Webb telescope and the current Wilkinson Microwave Anisotropy Probe-WMAP, which is being used to study the microwave radiation to understand the nature of the universe.
The third legront point is the opposite of the Earth on the other side of the sun in such a way that the Sun is always between this point and the Earth. In this situation, the satellite can never contact the Earth. The highly stable Lagrange point is L4 and L5, which is in the orbit of the Earth's Sun in the orbit around 60 Degrees in front and rear. On these points, the twin solar terrestrial relations Observatory (STEREO) is circling and making three-dimensional images of the sun.
Medium earth orbit
The satellite moves fast in the middle Earth orbit around the Earth. Two of these classes are distinctive, semi-synchronous and Molniya.
Semi-synchronous orbit is approximately circular or less decentralized and is 25560 km (20,200 km above surface) from Earth center. In this situation the satellite takes 12 hours to circumambulate the Earth. As the satellite moves, Earth also rotates down. In 24 hours, the satellite passes twice from one place. This class is consistent and stable, so it is suitable for satellite navigation satellites, the satellite of the Global Positioning System.
The second important orbit of middle earth orbit is the Molniya orbit. This class was searched by Russian scientists. This class is used for high latitudes. Satellites of the geocentric class get a steady perspective of the Earth but these satellites are on the equator, and in this situation, they are unsuitable for inspection of the North Pole or the nearby pole, because they are on the boundaries of these satellites. is. Molniya orbit is a good option in this situation.
Molniya orbit is highly decentralized. The satellite speeds up in a highly obsolete orbit where in one part the earth is closer. The satellite's speed is the highest in the nearest earth, because the gravity of the Earth gives it speed. As soon as he moves away from the Earth, his speed decreases and he spends most of the time in the classroom away from the Earth. The satellite completes the orbital phase in 12 hours, but at two-thirds of its time, it remains only on one hemisphere. Like semi-classical class, it also reaches twice in one place in 24 hours. This class is suitable for communication on nearby or near the North Pole.
Low Earth Orbit
Most scientific satellites and seasonal satellites are in circular low Earth orbit. The inclination of the satellite depends on its use. The Tropical Rainfall Measuring Mission (TRMM) satellite is for measuring rainfall in the tropical Pacific region. Therefore, this satellite has a lower tilt than 35 degrees so that it is mostly located above the tropatinic state.
Most of NASA and ISRO are in satellite polar orbit. In this highly inclined orbit, the poles move from the satellite pole and take 99 minutes to complete a revolution. In a parikrama, the satellite is in half-day-day part and half-time in the night part. The satellite does on the day-to-day part of the entrance to the pole.
When the satellite moves in its orbit, the earth rotates down. As soon as the satellite arrives again in the day part, it passes through the opposite place from the previous class. In 24 hours, the polar satellite passes through every place again, once in day time, for the second time at night time.
The way the Earth can be monitored by staying on top of the equator, the polar satellites can be monitored at constant time in one place. This class is called sun-synchronous, it means that whenever the satellite crosses the equator, the spatial time of that place on Earth will always be the same. For example, terra satellite when crossing the equator at 10:30 a.m. on Brazil, 99 minutes later, in its next revolution, when it crosses the equator from Ecuador or Colombia, then in Ecuador or Colombia Local time is 10:30 in the morning.
Sun synchronous classes are important in science, because in these classes, an attempt is made to keep the angle of the sun rays always on the surface of the earth (although the angle of the Sun's rays keeps changing according to the weather on the surface of the earth). That scientists can compare the photos taken in different years of the same weather without worrying about the sun's angles, light and shadows. Such comparison would be painless without the Sun synchronous orbit. The study of seasonal changes or climate change will be impossible without such comparison.
In the Sun synchronous orbit, the path of satellites is quite narrow. If the height of the satellite is 100 km then its orbital tilt of the Sun should remain in the synchronous orbit. It should be 96 degrees. Any change in both of these will make that satellite out of the sun synchronous orbit. Stretch caused by friction by the atmosphere and gravity of the Sun, Moon, make changes in the orbit of these satellites, so that these satellites have to keep continuously adjusting to remain in the solar system.
Getting and staying in orbit with satellite
Launch
The energy launch space used to launch a satellite depends on the height and orbital inclination of the orbit. Satellites need the most energy when they reach high earth orbit. The excessive orbital tilt like energy for polar orbit is more than the satellites moving on low axial tilting satellites such as the equator. A low-axial inclined satellite can reach its orbit using the Earth's rotation. The International Space Station is in the inclined orbit of 51.6397 Degree, so it is easy to reach NASA's space shuttle and Russian Soyuz. Wherever the satellite orbiting the pole does not get any help from the momentum of the earth, more energy is needed to reach the same height.
Stay in the classroom
Once the satellite has reached its class, it still has to do some work to remain in its class. The Earth is not a complete goal, its gravity is more than some other place. This irregularity in gravity and changes in the orbital inclination of the satellite, coupled with the pull of the gravitational pull of Sun, Moon, Jupiter. In its lifetime, the GOES satellites have to make changes three to four times to remain in their class. NASA's low Earth orbital satellites make changes in their orbital tilt once or twice a year once they remain in the solar system.
Satellites of low Earth orbit have been removed from their orbits by the pull of friction caused by the friction of Earth's atmosphere. These satellites pass under the thin surface of the Earth's atmosphere, but the resistance of air to that height is so much that it pulls the satellites to the Earth. Now the gravitation of the Earth gives them more speed than they are at higher altitudes. More speed more friction By increasing the satellite speed over time and decreasing the height, it can penetrate the spiral path in the Earth's atmosphere.
This stretch of the atmosphere is much stronger in solar activation because the atmosphere gives rise to the energy of the sun by giving extra energy to the atmosphere, like the atmosphere of some balloon. The outer thin layer of the atmosphere rises above it and takes its place from the bottom to a dense layer. Now the satellite is passing through a dense layer in the atmosphere while it was passing a relatively thin layer when the sun was not active. At the peak of the solar activities, the satellite has to face more resistance than passing through a denser layer. In the inactive period of the Sun, the satellites of low earth orbit have to change their class four times a year. But at the peak of solar activities, the satellite has to make changes in its class every two weeks.
The third reason for the change in the orbit of the satellite is space junk which can happen in the path of the satellite. On February 11, 2009, a communications satellite of the American satellite company Iridium collided with a passive satellite of Russia. The two satellites were broken and the two together made a space debris of 2,500 pieces. These 2,500 pieces were added to the database of 18,000 man-made objects moving in the orbit of the Earth, which the U.S. Space Surveillance Network.
The NASA Satellite Campaign Operator keeps an eye on every item coming in the path to its satellite. Every year at least four to five times the path of satellites has to be changed in order to avoid colliding with these debris coming in the way.
The Satellite Operations Team monitors these debris and other satellites of space, and accordingly they plan to change the path, elevation in the orbit of these satellites.
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