What are Satellites

The following guest article is brought to you by The Physics Society, in promotion of World Space Week 2020: Satellites Improve Life. Find out more at @thephysicsociety!

What is a satellite?

An astronaut is shown working outside of the International Space Station.
NASA astronaut Scott Kelly is working outside of the International Space Station during a spacewalk.
Photo by NASA on Unsplash

A satellite is anything that orbits a planet or star. It can be a man-made machine, or a natural satellite, like a moon or a star. Man-made satellites which orbit the Earth help us in our daily lives — taking data of our planet (which helps forecasting weather or crop yields), and the deep space beyond us, providing further insight into our universe.

Satellites carry cameras and scientific sensors, which gather crucial information about land, air, and water (when pointing towards Earth), and help collect fascinating data about our universe (when pointing towards outer space).

How does a satellite work?

Satellites come in many shapes and sizes, with two main core components: an antenna and a power source.  The antenna sends and receives information to and from Earth, and the power source keeps the satellite operational. Satellites are fitted with solar panels, allowing them to convert solar energy to electrical energy. 

A satellite will orbit the earth when its speed is balanced by the pull of Earth’s gravity (gravity keeps it in circular motion), without which it would accelerate in a straight line into space or fall back to Earth. Scientists have to take all these factors into account before releasing a satellite into orbit. Satellites can orbit Earth in geostationary orbit (west to east, in the same direction and rate as Earth’s spin to give it the appearance of being “stationary”) or polar orbit (north-south direction from pole-to-pole).

Satellites send and receive signals via radio waves, a type of electromagnetic radiation part of the electromagnetic spectrum. Since such rays don’t need a medium of particles to travel in, they can travel from the earth’s atmosphere into space where they are received by the satellite’s antenna. Nowadays, data (picked up by satellites) that may be relevant to us has been built into engines, such as Google and Bing.

What are the applications of satellites?

Photo by Ben Wicks on Unsplash

Satellites are used to relay information from one place to another. It can pick up on everything including phone calls and television broadcasts. They can also communicate to and from remote areas where ordinary telephones don’t work (e.g. mountains, dense rainforests, etc.)

On the other hand, satellites that take photographs of the Earth are often used to get a lay of the land, to make weather forecasts and to help scientists predict if a tsunami or earthquake may occur in the future, so it’s impact can be reduced.

Navigation satellites are the GPS that we use on a daily basis. They are used most often to determine the exact position, speed and direction of an object or a place almost anywhere in the world.

Satellites looking toward Earth provide information about our natural world: clouds, oceans, land, gases in the atmosphere (ozone, CO2), wildfires, smoke emitted by volcanoes, and countless other data points. This information helps scientists predict weather and climate, public health officials to track disease and famine. On the ground, it helps farmers know which crops to plant and when, and helps emergency workers respond to natural disasters.

Space-facing satellites have a variety of jobs. Some watch for dangerous rays coming from the sun. Others explore asteroids and comets, the history of stars, and the origin of planets. Some satellites fly near to or orbit other planets, with functions such as looking for evidence of water on Mars, or taking close-up pictures of Saturn’s rings.

This is a guest post written by The Physics Society. Find out more about the exciting lineup at World Space Week 2020!

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