Canadian Geographic
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Two basic types of sensor are used in Earth-observation satellites: active and passive.


Observing the earth from hundreds of kilometres above its surface provides a unique perspective. We can watch huge weather systems move from province to province; and we can use our home computers to zoom in on freely available satellite photos of just about any point on the globe. In fact, there are more than 100 satellites currently in orbit whose primary purpose is to observe the Earth and its atmosphere, not including military surveillance satellites. These satellites use a variety of tools – cameras, radars, infrared sensors – to obtain information about what is happening on land, in the oceans, and in the atmosphere.

Canada’s vast territory and the remoteness of its northern lands make satellites a particularly valuable tool. As polar ice continues to melt, Canadian satellites like RADARSAT-1 and RADARSAT-2 are playing a crucial role in monitoring changes to the environment, as well as ensuring the safety of ships travelling through northern waters. Elsewhere, satellites are used in tasks that range from detecting oil spills to mapping different kinds of land use, tracking the erosion of coastlines, and coordinating rescue operations.

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Quiz :

Who is the biggest user of RADARSAT images in Canada?

Canadian Ice Service
Canadian Avalanche Centre
Weather Office