What is a Satellite?
A satellite is something that orbits or goes around the planet or a star, and there are varieties of satellites existing in the sky. A natural thing present in the sky is the Moon.
There are many satellites, which are man-made and are launched into space for accomplishing a purpose like ISRO’s Mangalyaan satellite was launched into space for accomplishing the Mars Orbiter Mission, ICESat satellite was designed by NASA for getting an answer to questions related to earth’s climate system, global climate change and variations in sea levels, etc.
In this article, we are going to learn about earth’s satellites and the types of satellites.
Types of Satellite
The types of satellites are as follows:
Natural satellites
Artificial or man-made satellites
Let’s discuss these one-by-one:
Natural Satellite
A satellite that is existing naturally in the sky and orbits around the celestial body is called the natural satellite.
A natural satellite is an object that revolves around a body bigger than its size and humans have no role in their development or launching. These objects are often referred to as moons.
Moon is an astronomical body also called the natural satellite because it revolves around the earth.
The Fun Fact
There are 240 recognized moons within the solar system, involving 163 revolving around the planet, four orbiting around dwarf planets, and dozens of others revolving around the tiny solar bodies.
Artificial or Man-Made Satellite
Artificial is something related to the role of humans, and when satellite word gets added to it, it becomes a man-made satellite. One of the most widely known examples is the earth’s satellite.
They are around 1,100 artificial satellites orbiting the earth. An artificial satellite is a sort of spaceship that revolves around the earth. It is made of a computer, along with two solar panels to obtain power from the Sun.
They do have cameras or other scientific tools to help scientists gather information.
History of a Man-Made Satellite
If we look back to the time in 1687, a great Physicist and Mathematician, Sir Isaac Newton was the first person to suggest the idea of an artificial satellite in his book named Philosophiae Naturalis Principia Mathematica.
Nearly three years after Newton discovered his theory on artificial satellites, the Soviet Union launched its first-ever Earth’s satellite named Sputnik 1 on October 4, 1957.
Sputnik 1 was about the size of a beach ball and it was able to circle the earth every 96 minutes and its radio signals were heard by scientists & radio operators worldwide.
Following the Soviet Union, three months later, on January 31, 1958, the US launched its first satellite named Explorer 1. This satellite was smaller than Sputnik 1.
This satellite was designed to detect radiation and it helped discover the core of the two Van Allen Radiation Belts.
Van Allen Radiation belts are a zone of the electrically charged particles that borders the Earth.
From these two examples, we understood what satellites are used for.
What are Satellites Used for?
One of the unimaginable things is, there are around 2000 satellites revolving around the earth simultaneously, all these satellites do a unique job.
For example, by gathering data or pictures of the earth’s surface, the scientists can learn about the temperature of the oceans, and observe what's happening in the earth’s glaciers and discover the different types of ice in the universe.
Satellites help meteorologists study the weather and also about big storms like hurricanes, cyclones, etc.
So, not only scientists use satellites, we as a person, with the help of our cell phones, also use the satellite for detecting our location’s week-wise weather and Maps for tracking the location.
The Fun Fact
The biggest planet rotating around the earth is NASA's International Space Station, it is as huge as a soccer/football field.
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Usually, six astronauts reside in this station for about six months to perform cool science experiments, which isn’t possible on the earth.
The interesting thing is, you can view this satellite in the dark nights as a point of light continuously (with no blinking) moving steadily as a straight line all around the sky.
Projectile Nature of a Satellite
The projectile nature of a satellite is because of the force of gravity. It’s because when a satellite is launched in space, the only governing force for the satellite’s motion is the force of gravity.
To keep the satellite in space, it is required to maintain a balance between gravity and velocity because the earth’s gravitation is pulling it down and at the same time it is speeding forward just like a cannonball firing.
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To keep this satellite at the desired altitude, we must learn about the orbital velocity. So, when the satellite is close to the earth, it must travel faster to escape the earth, otherwise, it will fall into the earth (when the launching speed = 8000 m/s).
When a satellite is launched at a speed equal to 8000 m/s, it orbits the earth in a circular path.
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Further, increasing the speed, the satellite makes an elliptical path around the earth.
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FAQs on Earths Satellites
1. What is a satellite, and what is Earth's primary natural satellite?
A satellite is any object that orbits a larger celestial body under the influence of gravity. Earth has one natural satellite, which is the Moon. In addition, there are thousands of artificial satellites, which are human-made objects launched into space for various purposes.
2. What is the fundamental difference between a natural and an artificial satellite?
The main difference lies in their origin. A natural satellite is a celestial body that was formed naturally and is gravitationally bound to a planet, like the Moon orbiting Earth. An artificial satellite is a machine constructed and launched by humans into a specific orbit to perform tasks such as communication, navigation, or scientific research.
3. How do artificial satellites stay in orbit without falling back to Earth?
A satellite stays in orbit due to a precise balance between its forward motion (tangential velocity) and the Earth's gravitational pull. Gravity continuously pulls the satellite towards the Earth, but its high speed causes it to constantly 'miss' the planet, resulting in a stable, curved path called an orbit. It is essentially in a state of continuous free-fall around the Earth.
4. What are the main types of satellite orbits around Earth?
Satellite orbits are primarily classified by their altitude and orientation. The main types include:
- Low Earth Orbit (LEO): At an altitude of 160 to 2,000 km. Satellites in LEO travel at very high speeds and are ideal for imaging and scientific observation, like the International Space Station (ISS).
- Medium Earth Orbit (MEO): Located between LEO and GEO, typically around 20,000 km. This orbit is mainly used by navigation satellites, such as those for the Global Positioning System (GPS).
- Geostationary Orbit (GEO): At an altitude of 35,786 km above the Equator. Satellites here have an orbital period of 24 hours, matching Earth's rotation. They appear stationary from the ground, making them perfect for communication and weather broadcasting.
5. What is the difference between a geostationary satellite and a polar satellite?
The key difference is their orbital path and purpose. A geostationary satellite orbits above the Equator at a very high altitude, remaining fixed over one spot on Earth, which is ideal for broadcasting signals to a specific region. In contrast, a polar satellite flies in a north-south path over the poles at a much lower altitude, allowing it to scan and map the entire surface of the Earth over several orbits. This makes it suitable for remote sensing and environmental monitoring.
6. How does a satellite's required orbital speed change with its altitude?
A satellite's required orbital speed is inversely related to its altitude. The closer a satellite is to Earth, the stronger the gravitational pull it experiences, so it must travel at a higher velocity to maintain its orbit. Conversely, a satellite at a higher altitude experiences weaker gravity and can maintain a stable orbit with a lower velocity. For instance, satellites in LEO travel much faster than those in GEO.
7. What are the most important applications of artificial satellites in modern life?
Artificial satellites are crucial for many technologies we use daily. Key applications include:
- Communication: Relaying telephone calls, television broadcasts, and internet data across the globe.
- Navigation: Providing precise location and timing information through systems like GPS.
- Weather Forecasting: Monitoring cloud patterns, storms, and atmospheric conditions to predict weather.
- Earth Observation: Tracking changes in climate, deforestation, and polar ice caps, as well as being used for mapping and resource management.
- Scientific Research: Studying Earth, our solar system, and distant galaxies with instruments like the Hubble Space Telescope.
8. Why is it necessary to launch a satellite with a horizontal velocity to achieve orbit, instead of just launching it straight up?
An orbit is a path of continuous falling around a planet, which requires a significant horizontal or tangential velocity. If a satellite were launched straight up, it would either fall back to Earth once its initial thrust is exhausted or, if it reached escape velocity, it would fly away into space. To achieve an orbit, the satellite must be given enough forward speed parallel to the Earth's surface so that as gravity pulls it down, its path curves to match the curvature of the Earth.
