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Regional and Mesoscale Meteorology Branch

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Satellites

First things first: do you know what is a satellite? Lots of people think about sci-fi movies or NASA as soon as they hear the world satellite. By definition, satellites are much simpler to understand: any object with some mass orbiting – that is, within the orbit of – another object with mass is a satellite. That’s why we say the Moon is a satellite of the Earth. Now answer this: is Earth a satellite? The answer is yes! Because our blue planet orbits the Sun, it is also a satellite of the sun – just like all the other planets in our solar system have their own satellites, or moons, and are also satellites of the Sun.

SatellitesThe many different artificial satellites in Earth’s orbit and our main natural satellite – the Moon. Credit: NASA

Now that we know what satellites are, let’s talk about the two different categories of satellites: natural and artificial. Our moon is a natural satellite of Earth – that is, nobody purposely put the Moon where it is; it happened naturally, throughout a long period of time. You probably guessed the second category: artificial satellites, those who involve a lot of work by scientists and engineers, who after a lot of testing and calculations launched a man-made object into space, and that object are up there in Earth’s orbit. That object is what you probably think of when picturing a satellite: some metal shape at the center of a few shiny solar panels. However, even the International Space Station (ISS) is an important artificial satellite that also performs principal research about space.

ISS

The impressive International Space Station, a VERY large artificial satellite on Earth’s orbit. Credit: NASA

Artificial satellites are very important for us to forecast the weather or try to understand why, for example, hurricanes move the way they move. Satellites sense things like light to give us important information about our atmosphere – all the gaseous space surrounding Earth, where the weather “happens.” That information can be temperature, clouds’ height, wind direction, and even the composition of the air we breathe in every day. Do you want to how do satellites capture all that? Then keep reading the next article, “How they ‘see’”.

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Think about your five senses: sight, hearing, smell, taste, and touch. Those five are extremely important for you to understand the world around you. For example, if you grab a bowl of soup and you sense a lot of warmth coming from it, you most likely will try to blow on it a little before putting it in your mouth, right? You just used information given by your sense of touch to prevent a bad burn. Perhaps you even saw a bit of vapor coming out of that soup and that’s what told you the liquid was still too hot to be eaten. That’s your sight helping you to prevent that burn! Your body has billions of sensors to give you important information about your surroundings at all times – just like satellites from far away will use artificial sensors to capture atmospheric information and provide us with tons of really useful information.

There are currently 2,666 artificial satellites orbiting Earth – that’s right, we have thousands of objects up there in Earth’s orbit transmitting information 24/7 to governments and organizations all around the globe. Throughout history, more than 9,000 satellites were launched! Those satellites carry all sorts of sensors – it would take us a very long time to talk about them all, and by the time we finished, we probably would have new satellites to talk about; just last year, 95 new satellites were launched from Earth.

So how about we learn a little more about the satellites we use here at CIRA? The information we receive from space comes from two types of satellites: polar and geostationary satellites. The names may help you to guess their major difference; polar satellites move “from pole to pole,” in the directions we understand as south and north, and they give us images from the entire globe, sensing each point of the planet twice a day. Geostationary satellites, on the other hand, are important because they are designed to follow the Earth’s rotation; this means they sense the information of the spot they are meant to observe at all times. Here at CIRA, we watch very closely the information captured by the Geostationary Operational Environmental Satellites (GOES), a series of satellites created to watch over the western hemisphere of our globe and give us important information about winds and clouds that help us to prepare for hurricanes and wildfires – amongst many other functions!

 

At CIRA, we process information from two types of satellites: polar and stationary. The most important difference between those types is their planned orbit. As you may know, when a satellite is launched, very important calculations are made by scientists and engineer to ensure the object remains rotating at an exact, planned speed, path and distance from Earth. And those three characteristics give us very different data to study. Below you can find more about each type; check the comparison table below for a summary of the differences between polar and geostationary satellites.

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Polar:

Polar satellites are given this name because they are designed to move “from pole to pole,” in the directions we understand as south and north, and they give us images from the entire globe, sensing each point of the planet at least twice a day – one at daytime, one at nighttime, sometimes more depending on how geographically close to the pole a location is. It takes the polar satellites we use 12 hours for a full rotation around the planet, and they are positioned in Earth’s polar axis at a distance much closer to our surface compared to geostationary satellites – about 530 miles or 850 kilometers away. To give you an idea, that’s about the equivalent of a roundtrip from New York City to Washington D.C. or a roundtrip from the north frontier to the south frontier of Colorado! [ADD POLAR SATELLITE ANIMATION]

The orbit and distance of a polar satellite to Earth makes them very good to capture information on global climate patterns and cycles, once the information is of the entire globe and fairly frequent. For example, a scientist researching a slow-evolving event – such as melting of the polar ice caps – can create a model that will put together those images generated twice a day and create a very good model to foresee how much of the fresh water in the poles are being melted into the ocean over the years.

Geostationary:

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The 1950s

You may have heard about the Cold War, an important historic moment when the United States and the extinct Soviet Union (URSS) battled against each other not using tanks and guns, but propaganda and threats – hence, they are “cold.” A big part of that was the Space Race – when both countries heavily invested in technology to “conquer” space first. While the soviets managed to put the first satellite into Earth’s orbit in 1950, the US solidified its presence in the late 1950s with a series of successful satellites launched – the beginning of our history of using remote sensing to help us understand better the planet we live in.

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