DEFINITION:

The single location where we can learn the most about our planet is found nowhere on Earth but high up above it. Today, images of our planet from orbiting satellites are acquired continuously; they have become powerful scientific tools to enable better understanding and improved management of the Earth and its environment.

Earth observation provides objective coverage across both space and time. In the long term, this monitoring of the Earth’s environment will enable a reliable assessment of the global impact of human activity and the likely future extent of climate change.

One major class of Earth observation instruments are termed optical because they obtain data by recording the Earth reflected energy across various wavelengths, including visible light and invisible infrared bands.

Other sensors known as radar instruments actively shine microwaves pulses down to Earth in order to record how these pulses get reflected back up to space. These instruments measure surface roughness instead of light or heat energy, and have the advantage of being able to see through cloud and darkness. A different type of instrument named a altimeter records very precisely the time it takes for a microwave or laser pulse to be bounced back to the satellite, measuring both land and sea height to an accuracy of a few centimetres.

The make-up of the Earth’s atmosphere is also the subject of Earth Observation monitoring. Atmospheric instruments work by detecting how the envelope of air surrounding our planet affects light, heat or radio energy passing through it. Certain ‘signature’ spectral wavelengths either absorbed or emitted by the atmosphere indicate the presence of associated chemicals and gases.

Earth observation techniques are also applied by satellites orbiting another objects in the universe to study them and their environments.

(Source: PAE own elaboration from ESA’s web page: http://www.esa.int/Our_Activities/Observing_the_Earth/View_from_above )