Difference between active and passive sensors

What is an active sensor?
Active sensors create their own electromagnetic energy that is transmitted from the towards the terrain, interacts with the terrain producing a backscatter pf energy and is recorded the remote sensor's receiver.

What is a passive sensor?

The passive sensor detects the naturally emitted microwave energy within its field of view.

The main key difference between active and passive sensors are given below.

Active sensor : 
  • An active sensor is transducer generates electric current or voltage directly in response to environmental stimulation.
  • Active sensor both transmit and measure electromagnetic energy.
  • Active sensor self destructs during hijack attempts.
  • Active sensor actively transmits measurement to ground stations whether the personnel on duty want the data or not.
  • The active sensor emits their own EM energy which is transmitted towards the earth and receives energy reflected from the earth. The received EM(electromagnetic) energy is used for measurement purpose.
  • It provides their own energy source for illumination.
  • Active sensors are able to obtain measurement anytime.
  • Example of active sensor like communication satellite, earth observation satellite, LISS -1, etc.
Passive sensor :
  • The passive sensor is transducer produces a change in some passive electrical quantity such as capacitance, resistance or inductance as a result of the stimulation. These usually require additional electrical energy for excitation.
  • The passive sensor only measures electromagnetic energy.
  • The passive sensor has no defence against enemy attack.
  • Passive sensors wait patiently until data are requested.
  • The passive sensor receives naturally emitted EM energy within its field of view and performs measurement using it.
  • Passive sensors can only be used to detect energy when naturally when the naturally occurring energy is available.
  • Passive sensors can obtain measurement only in the day time.
  • Example of passive sensor like remote sensing satellite, SPOT-1, LANDSAT-1, etc.

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