What is a Satellite?
A satellite is a body that passes around some other body in a mathematically foreseeable path which is often called an Orbit. A communication satellite is nothing but a microwave repeater station in space that plays a significant role in telecommunications, radio, and television along with internet applications.
Here's some satellite history for you: the Soviet Union was the first country to launch an artificial satellite into space. The satellite was named Sputnik and launched on 4th October 1957. Sergei Korolev was its chief designer.
The satellite is structured such that it can power itself. The solar panels on the satellite generate solar power to run the satellite. The power is supplied to the propulsion system which has rockets to propel the satellite forward.
What is Satellite Communication?
Satellite communication is the technique of conveying data from one place to another using a communication satellite in the earth’s orbit. Watching your favorite movies or TV shows would have been impossible without this. A communication satellite is a mock or artificial satellite that is responsible for transmitting a signal using a transponder by creating a channel between the transmitter and the receiver which are located in two entirely different locations on earth.
Now, let us have a look at the advantages, disadvantages, and applications of satellite communications.
Satellite Communication – Advantages
There are numerous Advantages of satellite correspondences, for example, −
Flexibility
Ease in putting in new circuits
Distances are effortlessly taken care of and expense doesn't make a difference
Broadcasting conceivable outcomes
Each and every side of the earth is secured
Users can control the system
Energy is conserved since satellites use solar power
Satellite Communication − Disadvantages
Satellite correspondence has the accompanying disadvantages –
The introductory costs, for example, the segment and installation costs are excessively high.
Congestion of frequencies. This can cause a disruption of the communication services
Interference and proliferation
Satellite Communication − Applications
Satellite correspondence discovers its applications in the accompanying zones –
In Radio telecom.
In TV broadcasting, for example, DTH.
In Internet applications, for example, giving Internet connection for transferring data, GPS applications, Internet surfing, and so on.
For voice correspondences.
For innovative work, in numerous regions.
In military applications and routes.
The direction of the satellite in its orbit relies on the three laws called Kepler's laws.
Kepler’s Laws
Johannes Kepler (1571-1630) the galactic researcher, gave 3 progressive laws, in regards to the movement of satellites. The way pursued by a satellite around its essential (the earth) is an elliptical path. An eclipse has two foci - F1 and F2, the earth being one of them.
Kepler's First Law
Kepler's first law expresses that, "each planet rotates around the sun in a circular circle, with the sun as one of its foci." As such, a satellite moves in a curved path with the earth as one of its foci.
The semi-major axis of the ellipse is meant as 'a' and a semi-minor axis is indicated as b.
Eccentricity (e) − It is the parameter that characterizes the distinction of looking like an ellipse as opposed to that of a circle.
Semi-Significant Pivot (a) − It is the longest distance across drawn joining the two foci along the middle, which contacts both the apogees (farthest purposes of an oval from the inside).
Semi-Minor Axis (b) − It is the most limited distance drawn through the middle which contacts both the perigees (briefest purposes of an oval from the inside).
These are very much portrayed in the accompanying figure.
(Image to be added soon)
Kepler's Second Law
Kepler's second law expresses that, "For equivalent periods, the area covered by the satellite is equivalent to the focal point of the earth." It very well may be comprehended by investigating the accompanying figure.
(Image to be added soon)
Assume that the satellite covers p1 and p2 separations, in a similar time stretch, at that point the regions B1 and B2 shrouded in the two examples respectively, are equivalent.
Kepler's Third Law
Kepler's third law expresses that, "The square of the intermittent time of the orbit is corresponding to the cube of the mean separation between the two bodies." The orbital working of satellites is determined with the assistance of Kepler's laws.
Alongside these, there is something essential that must be noted. A satellite, when it rotates around the earth, experiences a pulling force from the earth which is the gravitational force. Likewise, it encounters some pulling force from the sun and the moon. Subsequently, there are two forces following up on it. They are −
Centripetal Power − The power that will in general draw an item moving directly towards itself is called centripetal power.
Centrifugal Power − The power that will in general push an item moving directly away from its position is called radiating power.
In this way, a satellite needs to adjust these two powers to keep itself in its circle.
Types of Satellites and Applications
Communications Satellite.
Remote Sensing Satellite.
Navigation Satellite.
Geocentric Orbit type satellites - LEO, MEO, HEO.
Global Positioning System (GPS)
Geostationary Satellites (GEOs)
Drone Satellite.
Ground Satellite.
FAQs on Satellite Communication
1. What is meant by satellite communication?
Satellite communication is a method of transmitting information from one point on Earth to another using an artificial satellite orbiting the planet. An Earth-based station sends a signal up to the satellite (the uplink), which then receives, amplifies, and retransmits the signal back to a receiving station on Earth (the downlink). This process effectively uses the satellite as a powerful microwave repeater in space.
2. How does satellite communication work in simple steps?
The process of satellite communication follows a clear path:
- Uplink: A ground station, or transmitter, sends a highly focused signal in the form of electromagnetic waves to a specific satellite in orbit.
- Processing: The satellite's onboard equipment, primarily the transponder, receives this signal. It amplifies the weak incoming signal and changes its frequency to avoid interference with the uplink signal.
- Downlink: The satellite then transmits the processed signal back towards Earth, where it is captured by one or more ground-based receiving dishes.
3. What is the basic structure of a communication satellite?
A typical communication satellite is composed of several key subsystems working together:
- Communication Payload: This includes the antennas to receive and transmit signals and the transponders that process them.
- Power Subsystem: This consists of solar panels to generate electricity from sunlight and rechargeable batteries to provide power when the satellite is in Earth's shadow.
- Propulsion System: Small rocket engines or thrusters are used to make precise adjustments to the satellite's orbit and orientation, a process known as station-keeping.
- Command and Control Subsystem: This is the satellite's 'brain', which communicates with ground control stations to monitor its health and execute commands.
4. What are the key applications of satellite communication in our daily lives?
Satellite communication is integral to many modern technologies. Key examples include:
- Television Broadcasting: Direct-to-Home (DTH) services that beam TV channels directly to our homes.
- Internet Services: Providing broadband internet access, especially in remote or rural areas where laying fibre optic cables is not feasible.
- GPS Navigation: The Global Positioning System (GPS) in our phones and vehicles relies on signals from a constellation of satellites to determine precise location.
- Weather Forecasting: Weather satellites constantly monitor atmospheric conditions, helping to predict weather patterns and track storms.
- Long-Distance Communication: Facilitating international phone calls and providing communication links for ships, aircraft, and remote operations.
5. What is the difference between a geostationary and a polar satellite?
The primary difference lies in their orbits and applications. A geostationary satellite orbits the Earth above the equator at an altitude of approximately 35,786 km. Its orbital period is exactly 24 hours, matching Earth's rotation, so it appears stationary from the ground. This is ideal for broadcasting and communication. In contrast, a polar satellite flies in a low-altitude orbit that passes over or near the Earth's poles. This allows it to scan the entire surface of the planet over successive orbits, making it perfect for applications like mapping, surveillance, and weather monitoring.
6. How do Kepler's laws of planetary motion apply to artificial satellites?
Kepler's laws, originally described for planets, are fundamental to understanding the motion of artificial satellites orbiting Earth:
- Kepler's First Law (Law of Orbits): A satellite's path around Earth is an ellipse, with the Earth at one of the two foci. A circular orbit is just a special case of an ellipse.
- Kepler's Second Law (Law of Areas): The line joining the satellite and the Earth sweeps out equal areas in equal intervals of time. This means the satellite moves fastest when it is closest to Earth (perigee) and slowest when it is farthest away (apogee).
- Kepler's Third Law (Law of Periods): The square of the satellite's orbital period is directly proportional to the cube of the semi-major axis of its orbit. This law helps calculate the exact altitude required for a specific orbital period, like the 24-hour period of a geostationary satellite.
7. Why is there a noticeable signal delay in satellite communication?
The signal delay, or latency, in satellite communication is due to the immense distance the signal must travel. For a call routed through a geostationary satellite, the signal must travel from Earth to the satellite (~36,000 km) and back to Earth (~36,000 km). Even traveling at the speed of light, this round trip causes a delay of approximately 250 milliseconds or more. This propagation delay is often perceptible in real-time applications like live interviews or international voice calls.
8. What are the major advantages and disadvantages of using satellite communication?
Satellite communication offers unique benefits but also has specific drawbacks.
Advantages include:
- Wide Coverage: A single satellite can cover a vast geographical area, connecting distant locations.
- Accessibility: It can provide connectivity to remote and inaccessible regions like mountains, deserts, and islands.
- Flexibility: New communication circuits can be established quickly without the need for extensive ground infrastructure.
- High Initial Cost: Designing, building, and launching a satellite involves significant expense.
- Signal Latency: The propagation delay can be a problem for real-time, interactive applications.
- Atmospheric Interference: Signals can be weakened by atmospheric conditions, a phenomenon known as 'rain fade'.
9. What is a transponder and what is its role in a satellite?
A transponder is a crucial electronic device within a satellite's communication payload that acts as a sophisticated repeater. Its primary role is to receive the weak incoming uplink signal from a ground station, amplify it to a higher power level, and then re-transmit it back to Earth on a different, lower frequency (the downlink). By changing the frequency, the transponder ensures that the powerful transmitted signal does not interfere with the faint incoming signal.
10. Why is satellite communication so crucial for a vast country like India?
For India, with its diverse and challenging geography, satellite communication is essential for several reasons. It helps in:
- Connecting Remote Areas: Providing telephone and internet services to geographically isolated regions like the Himalayan states, northeastern regions, and island territories like Andaman & Nicobar.
- Disaster Management: Establishing reliable communication links for rescue and relief operations when terrestrial networks are damaged during natural calamities.
- Education and Telemedicine: Supporting distance learning programs (like EDUSAT) and providing remote medical consultations to rural areas.
- National Security: Ensuring secure and dependable communication for military and defence applications across the country.
