Earth orbits the Sun; the moon orbits the earth. Like this, an artificial satellite orbits the earth. In other words, a satellite is a machine that contains solar panels, batteries, transmitters and receivers, control motors, scanners, cameras, etc. according to the purpose of the satellite. Satellite also called space machine. In this article, we will discuss about satellite and satellite communication in detail.
All man-made satellite orbits the earth for different purposes such as communication, weather forecast, taking photos, TV signals, phone calls and internet signals, GPS, etc. The speed of satellite may vary according to the purpose of satellite.
We imagine an imaginary line 100KM above the surface of the earth which is called the Karman Line. From the above of this Karman line, the satellite area starts. According to the height, satellites are divided into three parts: low earth orbit satellites, medium earth orbit satellites, and high earth orbit satellites.
Normally, the speed of a Satellites which are made for taking photos and scanning is faster than others. These satellites orbit the earth from a lower height. These satellites normally orbit the earth from 160 KM to 2000 KM height. Normally these satellites complete a single orbit within 90 minutes.
The satellites which are used for navigation and GPS (Global Positioning System) are little-it faster. They will take 10-12 hours to complete their single orbit. These satellites normally orbit the earth from 2000 KM to 35,700 KM height.
Other satellites which are used for communication purposes are also called high-earth-orbit satellites. These are 36000km far from the earth. These satellites move at the speed of the earth. It means these satellites complete an orbit within 24 hours.
These satellites always will be at the same point above the earth because of the same speed of satellite and earth. These need to be at the same point because, if these move to another location then the communication system will not work because of the far distance.
For example: If Nepal has a communication satellite for the Internet or phone calls. It must be in Nepalese Sky or Space (Space just above the map of Nepal). Its speed is same as the earth speed because it must move with the earth and always will be in the Nepalese Sky to work properly in Nepal. So, communication satellites will be at the same point of space always from earth because these move with the earth.
How do Satellites Actually work?
Till 2022, more than 8000 satellites in space. All these satellites helping us directly and indirectly. All these man-made satellites are orbiting earth regularly without any external energy because of gravitational force and centrifugal force.
We all have a question how do satellites stay in space? Why satellites don’t fall back to the earth? Satellites do not have any fans like Aeroplane and Helicopters or they do not have any external energy to stay in space.
Most of people think that there is no gravitational force in space. So, satellites stay in space. But it is a misunderstanding of people. Because the gravitational force of earth will decrease with the height but there is also gravitational force in space.
When a rocket deployed a satellite in space at a specific speed then there is no atmosphere in space. The sufficient speed of the satellite balances gravitational force and centrifugal force. So, the speed of a satellite will not be decreased because there is no atmosphere and it will be orbiting the earth continuously.
The country that launched the satellite in space will decide the speed of the satellite according to its purpose. There are earth stations to monitor the satellites’ speed, health, distance, location, orbit, etc. with the help of tracking system. So, it will complete an orbit of earth within a specific time such as 3 hours, 12 hours, 24 hours, etc.
Why do Satellites need Solar Energy?
We know that satellites will not use any external energy for orbiting the earth. We can see all satellites have solar panels and batteries in photos and videos why? This solar energy is used to control the satellites from the earth.
If any satellites lose their orbit, then there is a chance to crash, collide with other satellites and fall back to the earth, etc. So, with the help of control motors, we can control the satellite from the earth and put it back into the original orbit.
This energy is also used for Sens the orbit, to operate cameras and for other internal functions. The position and thruster are monitored by earth station. Earth stations also monitor on health and speed of satellites with the help of a tracking and telemetry control system.
The full form of GPS is Global Positioning System. It is a satellite-based radio navigation system. In the first time, the US government launched the GPS satellite for military purposes. The first satellite was launched in 1978AD for the Global positioning system. At this time the GPS system is only available for the US government or US military. In 2000AD GPS system fully opened for civilians.
The GPS satellites complete their Orbit within approximately 12 hours(11 hours and 58 minutes). The phones which have location feature available on the device, these all devices have a GPS unit. In this GPS unit, there is a GPS receiver that can receive the signals of GPS satellites. GPS system needs at least 24 satellites to cover up earth.
To know the position of anyone, GPS systems use trilateration mathematical technology. We can understand the trilateration mathematical system with the help of an example. Suppose you are going to point ‘B’ by bus, from point ‘A’. After starting your journey you know that you are far from 100KM from point ‘A’. Then, in this case, we know that we are 100KM far from point ‘A’ but at which point of the earth. It means you may be in the east, west, north, and south. So, we need three satellites to know the exact position.
Now you have a question, we should need 4 satellites to find out East, West, North, and South but why do we need only three satellites to know the exact location? Our phone needs to receive signals from 3 satellite to know the exact location. But, if there is access of 4 satellites then there is a high chance to be an accurate result. We need only three satellites to know 4 directions because we assume earth as a fourth satellite.
So, with the help of other three satellites, we can find longitude and latitude. The point where three satellites’ area (circle) intersects with each other, is our exact location. It means we know, we are something degree and something minute East, something degree and something minute in West, something degree and something minute in north and South with intersecting point or coordinate point. There is also Automic clock which helps to know the exact time.
Does GPS need internet or not?
We think the internet is compulsory to operate GPS system on our devices. This is a misconception because GPS system does not need any internet for navigation. A-GPS does not work without data service but GPS radio can still get fix directly form the satellites if it needs to.
You can use your google map in offline mode also. If you have downloaded a map, you can use navigation in offline mode also. In this case, we need the internet to download Google Maps, not for navigation. If you have already downloaded a map then you can use in offline mode also.
Advantages of satellite communication
- The most significant advantage of satellites is they can cover a large area for communication. A single satellite can cover 1/3 area of earth.
- The oceans, hills, forests, mountains, and rivers cannot affect satellite communication.
- Satellite communication is easy to maintain than ground fiber cable. The maintenance cost of satellites is less than fiber cable.
- It is best for remote area communication.
- Satellites are made with high-quality components. So, it is more reliable than others.
- High capacity in comparison to terrestrial networks.
- Quick setup time with bandwidth in demand.
- In satellite communications, fairness in service. It means all users can get the same internet speed.
Disadvantages of satellite communication
- Satellites are highly expensive. So, satellite communication or the satellite internet is more expensive than fiber communication.
- Due to low gain antennas, there is a crowded bandwidth most of the time.
- After launching a satellite, it is difficult to change anything. In other words, satellites are non-repairable.
- Communication satellites are 36000km far from the earth. So, there is a 0.25-second delay between transmission and reception of signal. This time delay reduces the efficiency of satellites in data transmission.
- Designing and lunching cost of satellites are expensive.
- In case of bad weather conditions, there is a low chance of getting better response or speed of internet