Why do we need Earth Observation Satellites?

Earth Observation Satellites use a variety of imaging payloads to track changes on the surface of the Earth. These satellites provide global data on environmental changes, natural disasters and human activities. Without satellites, tracking climate change, deforestation and urban growth would have to rely on slow and incomplete ground-based methods. The timely, wide-area information allows scientists, businesses and governments to make timely, informed decisions. The satellites can detect diseases in crops, floods in realtime, push out alerts when forest fires break out, and monitor pollution levels. 

Earth observation satellites use a variety of sensors, each with unique capabilities. Optical sensors are in demand for realtime satellite views of targets of interest. Resolution and timely coverage are the requirement from such satellites. Hyperspectral sensors record colours in additional wavelengths than the three or four used in conventional cameras, allowing for identification of minerals or materials based on their characteristic wavelengths. Thermal sensors that are not widely used, can reveal heat variations in urban areas and industrial sites even in the night, and can even be used for archaeology. 

Synthetic Aperture Radar (SAR) uses microwave signals to create images. Unlike optical methods, SAR works through clouds, in day or night, providing reliable data even in adverse weather conditions. SAR compliments optical imagery by filling in the gaps. These technologies have a wide range of applications including environmental monitoring, urban planning, assessing landslide risks, tracking of emissions, monitoring of heat islands, and detection of oil spills. These satellites allow governments to keep a watch on troop and equipment movements along international boundaries, and are essential for national security.