satellite

Learning objectives

By the end of this lesson, you should be able to;

• Define satellite.
• Describe the classification of satellites.
• Define and describe orbit.
• Describe major parts of a satellite.
• Describe how satellites orbit the earth.
• Describe the applications of satellites.

The term satellite broadly refers to planet, moon or machine that orbits a star or planet. For example, earth is considered a satellite because it orbits around the sun. Likewise, the moon is also considered a satellite because it orbits around the earth.

There are two different types of satellites– natural and man-made. The moon and the earth are examples of natural satellites. Thousands of man-made or artificial satellites orbit the earth today. Some of these satellites are for taking pictures of the planet to help meteorologists to predict weather as well as track hurricanes. Some satellites take pictures of the sun, dark matter, black holes, planets, and far-away galaxies to help scientists to understand the solar system and the universe.

Other satellites are mainly used for communication; in the beaming of telephone calls and TV signals around the world. Note that, the global positioning system is made up of more than 20 satellites. This helps everyone with a global positioning system receiver to figure out their location.

Classification of satellites

• Astronomical satellites. These satellites are applied to observe distant galaxies, planets, and other outer-space objects.
• Biosatellites. These are satellites applied to carry living organisms, mainly for purposes of scientific experimentation.
• Communication satellites. These are satellites positioned strategically in space for purposes of telecommunications.
• Earth observation satellites. These satellites are applied for uses like map making, meteorology, and environmental monitoring.
• Navigation satellites. They use radio time signals to transmit and enable receivers on the ground to establish a location.
• Crewed space craft or spaceships. These are big satellites that can carry humans to and beyond the orbit of the earth.
• Miniaturized satellites. These are of unusually small sizes and low masses. These satellites can be classified further into: Mini satellite (500 to 1000 Kilograms), microsatellite (below 100 Kilograms), and Nano satellites (below 10 Kilograms).
• Reconnaissance satellites. They are communications or earth observation satellites deployed for intelligence or military operations.
• Recovery satellites. These satellites provide a recovery of biological, reconnaissance satellites, and other loads from the earth’s orbit.
• Weather satellites. They are used for weather monitoring purposes.
• Space stations. These are artificial structures found at the orbit of the earth designed to host human beings in outer space.

Orbits

The first satellite to reach the orbit of the earth was the Sputnik 1, and was put in an orbit called the geocentric orbit.  It is the most common orbit, and has about 3,000 artificial satellites that orbit the earth and are active. Geocentric orbits can be classified further on basis of their inclination, altitude, and eccentricity.

The most commonly used types of geocentric orbit are: low earth orbit, medium earth orbit and high earth orbit. Low earth orbit is made up of orbits below 2,000 kilometers. Medium earth orbit contains orbits between 2,000 and 35,786 kilometers. High earth orbit is made up of orbits higher than 35,786 kilometers.

Parts of a satellite

Satellites come in many sizes and shapes. However, most satellites have two parts in common; the antenna and a power source. The work of the antenna is to send and receive information. This is mainly to and from earth. The power source may be a battery or a solar panel. Many satellites also have scientific sensors and cameras. Satellites may point toward earth to collect information about its water, air and land, or they may point toward space to gather information from the solar system and universe.

How do satellites orbit the earth?

Rockets are used to launch most satellites into space. A satellite is able to orbit the earth if there is a balance between its speed and the earth’s pull of gravity. A satellite would not be able to fly without this balance. Satellites orbit the earth at different heights and speed, and along different paths.

A geostationary satellite flies from west to east direction of the equator. It moves in a similar direction to earth, and at the same spinning rate as the earth. Therefore, from the earth this satellite looks stationary as it is found above in the same location.

Polar orbiting satellites fly from pole to pole in a north-south direction. As the earth’s spins below them, these satellites can scan the whole globe.

First satellite in space

Sputnik 1 was launched by the Soviet Union in the year 1957.

End of life of satellites

When satellites complete their mission, usually 3 to 4 years after launch, the satellite can be de-orbited or left in the same orbit but moved to a graveyard orbit. Satellites that were created in the early days were not designed to de-orbit due to high cost of developing such technologies.

Applications of satellites

• Weather. A weather satellite is mainly used to monitor weather and climate of the earth. Meteorological satellites also monitor sand storms, ice mapping, snow cover, energy flows, ocean currents, and effects of pollution.
• Environmental monitoring. Satellites can monitor the environment of the earth by checking; earth’s vegetation, ocean color, sea state, atmospheric trace gas content, and ice fields.
• Mapping. The terrain of the earth can be easily mapped with the help of satellites from space.

Summary

We've learned that;

• The term satellite broadly refers to planet, moon or machine that orbits a star or planet.
• The moon and the earth are examples of natural satellites.
• Thousands of man-made or artificial satellites orbit the earth today.
• Satellites come in many sizes and shapes.
• Some of the main applications of satellites include in the fields of; weather, environmental monitoring, and mapping.