A Satellite can be defined as an object orbiting around a larger object in space. A satellite is a moon, planet or machine that orbits a planet or star in outer space. For instance, the moon goes around the Earth, so we can say that it is a satellite of the Earth. We also know that space agencies like ESA, JAXA or NASA have launched many objects in the sky that orbit around the Earth or any other colossal body present in outer space. In addition, our ISRO (Indian Space Research Organisation) has launched many satellites to revolve around Earth or the moon like Chandrayaan-1, Chandrayaan-2, GSAT-1 or 2, etc. 

We can also say that Earth is a satellite of the Sun, but there are separate names for the objects those revolve around the Sun or any other star. We call them planets. One can learn more about satellites with the help of this article.

What is a Satellite?

A satellite is an object (ex: moon, Chandrayaan-1) that orbits another larger (as compared to itself) object (ex: Earth, Sun) in space. For example, the moon orbits the earth; hence, the moon is a satellite, and so was Aryabhatta (The first-ever artificial satellite launched by India). “Man-made satellites” are types of equipment designed to revolve around the earth or any other colossal body in our solar system when it is launched into space.

The moon is an example of a natural satellite. In addition, thousands of artificial or man-made satellites orbit the earth. The function of artificial satellites are:

a. To collect data around the planet that would help predict weather conditions and paths of cyclones or hurricanes to prepare and combat against adverse environmental conditions. Studying the pictures taken by the satellites of other planets, the Sun, black holes, dark matter, or faraway galaxies has helped scientists learn a lot more about our solar system.
b. Transporting the television and communication signals around the globe. The development of GPS, i.e. Global positioning system, has helped trace the exact position of people with GPS receivers like phones, tabs etc., at all times, thus, making the world a safer place.

A group of more than \(20\) satellites make up the Global Positioning System. Galileo published the earliest discovery of a moon of another planet other than the earth. Moon is the only natural satellite of the earth with a nearly circular orbit and a period of approximately \(27.3\) days, roughly equal to the rotational period of the moon about its axis. Mars has two moons, Phobos and Deimos, while Venus and Mercury have no moons.

Types of Satellites

Satellites can be of two types:
1. Natural satellites
2. Artificial satellites

Natural Satellites:

A natural satellite is any celestial body in space that orbits around a bigger body. Moons orbit planets, so they are called natural satellites. In a generalised sense, the term “moon” can be used to describe non-artificial satellites of planets, dwarf planets, or minor planets. Within the solar system, there are around (240) known moons which include (163) of those which are orbiting certain planets, four orbiting dwarf planets, and dozens more orbiting small solar system bodies.

Most of these natural satellites were formed from the discs of gas and dust circulating planets in the early solar system. However, some are believed to be objects formed elsewhere that fell into orbit around larger worlds.
So far, no natural satellites or sub-moons have been discovered that orbit the already existing natural satellite or a moon, i.e. there are No Moons to the Moons. Their stability is highly uncertain, and so their presence is highly unlikely.
The largest natural satellites in the solar system (those bigger than about (3,000) kilometres across) are earth’s moon, Jupiter’s Galilean moons (Io, Europa, Ganymede, and Callisto), Saturn’s moon Titan, and Neptune’s captured moon Triton.

Artificial Satellites:

An artificial satellite is a machine that people built and launched into orbit using rockets. Over a thousand active satellites are currently orbiting the earth. The design, size, and altitude of a satellite depend on its purpose. Satellites are launched into different orbits depending on their mission.

An artificial satellite has four parts. The first one is the power system with a solar or nuclear core that powers the satellite, a component that controls its orbiting path. Then, an antenna sends and receives information and a payload that collects information like a camera or a particle detector. The pieces of equipment used to build a satellite are hardened to withstand the presence of radiation and the vacuum of space.
Despite the earth’s gravitational pull, satellites don’t immediately fall back on earth as their angular velocity from launch is sufficient. The gravitational pull serves more as a string that keeps the body from being ejected out of orbit. Over time, however, many satellites lose their velocity and face degradation of their orbit, eventually burning up in the atmosphere.
Artificial satellites can have various missions, including scientific research, weather observation, military support, navigation, Earth imaging, and communications. Some satellites fulfil a single purpose, while others are designed to perform several functions simultaneously.

Types of Artificial Satellites

Two commonly used artificial satellites are:
1. Geostationary Satellites: Satellites in a circular orbit around the earth in the equatorial plane with a period of revolution of \(24\) hours are called Geostationary Satellites. The height of a geostationary satellite is \(h = 35800\,\rm{km}\), and its orbital velocity \(v = 3.1\,\rm{km/s}.\)
Since the earth rotates in the same period, the satellite would appear fixed from any point on earth. The higher frequencies correspond to the waves used in a television broadcast or other forms of communication, and thus it makes it quite hard to receive them beyond the line of sight. A Geostationary satellite stays largely fixed above the broadcasting station, and hence these signals can be received by it and can be broadcasted back to a much wider area on earth. The group of satellites launched by our country called INSAT are one such group of Geostationary satellites used for telecommunications in India.

2. Polar Satellites: These are low altitude (\(500\) to \(800\)) satellites, but they go around the earth’s poles in a north-south direction, whereas the earth rotates around its axis in an east-west direction.

A polar satellite crosses any altitude several times throughout the day, and its period of revolution is around \(100\) minutes. Its height above the earth is only about \(500 – 800\,\rm{km}\). Thus, only small strips of the earth can be seen by a camera installed on it in one orbit. The whole earth can be seen strip by strip as this satellite goes around the earth several times a day. Their proximity to the earth’s surface allows these satellites to view polar and equatorial regions at close distances with good resolution. The data collected from such satellites is extremely useful for remote sensing, meteorology, and environmental studies.

Some Other Types of Satellites

1. Weather satellites: As the name suggests, these satellites help meteorologists study the weather conditions across the landscape. A good example of such a satellite is the “Geostationary Operational Environmental Satellite (GOES)”.
2. Communications satellites: A communication satellite contains hundreds or thousands of transponders typically These satellites allow the audio and signal data exchange across the earth. Examples of such satellites include Telstar and Intelsat. Such Communications satellites are generally geosynchronous.
3. Broadcast satellites: These satellites broadcast television signals from one point to another (similar to communications satellites).
4. Scientific satellites: Various scientific missions are undertaken by such satellites. Currently, such satellites track almost everything from the motion of the rays to the Sun to the gamma spots.
5. Navigational satellites: These help ships, and planes navigate. The most famous is the GPS NAVSTAR satellites.
6. Rescue satellites: These satellites respond to radio distress signals.
7. Earth observation satellites: These satellites check the planet for changes in everything from temperature to forestation to ice-sheet coverage. The most famous are the Landsat series.
8. Military satellites: These satellites send highly sensitive and classified data containing information obtained by observing enemy movements, nuclear tests and provide warnings regarding missile launches, radar imaging, and photography.

Fun Facts About Satellites

1. Satellites can be in many shapes and sizes. Most satellites have at least two parts in common – a power source and an antenna. The antenna sends and receives information, often to and from the earth. Solar panels or batteries are used as the power source. Solar panels generate power by turning sunlight into electricity.
2. Satellites need rockets to launch them into space. A satellite orbits earth when the pull of the earth’s gravity balances its speed. The satellite would go straight line off into space or fall back to earth if there were no gravity. Satellites orbit earth at different heights, at different rates, and along different paths. The two common types of orbits are “geostationary” and “polar.”
3. It is rarely heard that there have been collisions between satellites. Satellites are placed into orbit after careful study to avoid other satellites. The orbits can change over time, which increases the chances of a crash as more and more satellites are launched into space. For example, in February 2009, two communications satellites – one American and one Russian – collided in space. This, however, is believed to be the first time two manufactured satellites have collided accidentally.
4. The satellites see the earth with bird-like eyes, allowing them to see large areas of the earth at one time. This gives an advantage to the satellites to collect more data quicker than instruments on the ground.
5. Satellites see into space with greater clarity than telescopes at the earth’s surface. That’s because satellites revolve on orbits above the clouds and dust in the atmosphere that may block the view from ground level.
6. Before satellites, TV signals couldn’t travel from one point on Earth to another because TV signals only travel in straight lines. So, they would quickly trail off into space instead of following the earth’s curve. Sometimes mountains or tall buildings would block them. Phone calls to faraway places were also a problem. Setting up telephone wires over long distances or underwater is difficult and is an expensive setup. After the satellites are placed, phone calls and TV signals are sent upward to a satellite. Then, almost instantly, the satellite sends them back down to different locations on earth.

Summary

A satellite is a heavenly object that orbits another larger (as compared to itself) heavenly object (ex: Earth, Sun). For example, the moon is a satellite because it orbits the earth, and so was Aryabhatta. The moon is an example of a natural satellite. In addition, thousands of artificial or man-made satellites orbit the earth. Galileo published the earliest discovery of a moon other than the earth. Sputnik 1, the world’s first artificial satellite, was launched into space by the Soviet Union on 4 October 1957, and since then, there has been no looking back.

Satellites can be of two types:
1. Natural Satellites: A natural satellite is any celestial body in space that orbits around a bigger body. Moons orbit planets, hence, they are called natural satellites.
2. Artificial Satellites: An artificial satellite is a machine that people built and launched into orbit using rockets. Over a thousand active satellites are currently orbiting the earth. The design, size, and altitude of a satellite depend on its purpose.

Types of artificial satellites:
(i) Geosynchronous Satellites: These are Launched straight into the geosynchronous orbit with an orbital period matching the earth’s rotation period. The geosynchronous satellites take 24 hours to complete one rotation around the earth.
(ii) Polar Satellites: These are low altitude (\(500\) to \(800\,\rm{km}\)) satellites, but they go around the earth’s poles in a north-south direction, whereas the earth rotates around its axis in an east-west direction.

Other types of artificial satellites:
A. Weather satellites: As the name suggests, these satellites help meteorologists study the weather conditions across the landscape. A good example of such a satellite is the “Geostationary Operational Environmental Satellite (GOES)”.
B. Communications satellites: A communication satellite contains hundreds or thousands of transponders typically These satellites allow the audio and signal data exchange across the earth. Examples of such satellites include Telstar and Intelsat. Such Communications satellites are generally geosynchronous.
C. Broadcast satellites: These satellites broadcast television signals from one point to another (similar to communications satellites).
D. Scientific satellites: Various scientific missions are undertaken by such satellites. Currently, such satellites track almost everything from the motion of the rays to the Sun to the gamma spots.

Uses of Artificial Satellites:
These artificial satellites perform several tasks like collecting data from around the planet that would help predict weather conditions and paths of cyclones or hurricanes to prepare and combat the adverse environmental conditions. Studying the pictures taken by the satellites of other planets, the Sun, black holes, dark matter, or faraway galaxies has helped scientists learn a lot more about our solar system.

Related Topics to Study

1. Earth 2. Solar System 3. Gravitational Force

FAQs

Q.1. What are satellites used for?
Ans: The satellites are launched with a specific objective in mind involving uses in the communication industry, research in scientific areas, forecasting the weather, and intelligence.

Q.2. What are some types of satellites?
Ans: Based on their use, we have the following types of satellites:
Communications Satellite.
Remote Sensing Satellite.
Navigation Satellite.
Global Positioning System (GPS)
Geostationary Satellites (GEOs)
Drone Satellite.

Q.3. Can I see my house in real-time?
Ans: Yes, the satellites placed in lower orbit around the earth have enabled us to watch our houses in real-time, and the same satellites have made GPS navigation a reality.

Q.4. What is a satellite for kids?
Ans:  A satellite is a body that is revolving continuously in orbit around a comparatively much larger body. Satellites are of two types natural and artificial. Natural satellites like the moon revolve around our earth, and artificial satellites like INSAT or GSAT have been launched by us to orbit around the earth for various scientific purposes.

Q.5. How can you identify a satellite?
Ans: Watch the sky closely in the dawn or dusk hours, and you’ll likely see a moving “star” or two sliding by through the sky. These are satellites, or “artificial moons” placed in low Earth orbit. These shine via reflected sunlight as they pass hundreds of kilometres overhead.

We hope you find this article on Satellite helpful. In case of any queries, you can reach back to us in the comments section, and we will try to solve them.