Natural Resources Canada > Earth Sciences Sector > Priorities > Canada Centre for Remote Sensing
Active and Passive Imaging Systems
5.2 Active and Passive Imaging Systems
Active and Passive Radar Imaging Systems |
Active and Passive Radar Imaging Systems |
Active and Passive Radar Imaging Systems |
Imaging radar systems can be active or passive. Active radar systems transmit short bursts or 'pulses' of
electromagnetic energy in the direction of interest and record the origin and strength of the backscatter received from objects within the system's field of view. Passive radar systems sense low level microwave radiation given off by all objects in the natural environment.
RADARSAT-1 |
Radar imaging systems such as ERS (European Remote Sensing Satellite), JERS (Japan Earth Resources Satellite),
and RADARSAT-1 are active systems. They both transmit and receive energy. Microwave scanning radiometers only receive microwave energy. The Japanese MOS (Marine Observation Satellite)  and JERS satellite systems employ microwave scanning units. Since the source is a very low level of electromagnetic energy, this type of data is prone to noise.
One advantage of active radar sensing systems is that, since they provide their own source of energy, they can collect data at any time of the day or night. Passive sensors - optical, thermal, and microwave - rely on receiving the naturally emitted or the sun's reflected energy from the Earth's surface.
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