Basic Measurements

How do sensors work?

Image of GOES satellite created by Goddard Space Center

Remote Sensing is the acquisition of data and information of an object by a sensor that is not in physical contact with it. Our eyes are sensors that are able to acquire data from the visible part of the electromagnetic (EM) spectrum,see illustration for Electromagnetic Spectrum below. However, the universe emits energy across the entire EM spectrum. Today, we are able to design sensors and place satellites inorbits that allows us aqcuire data that, until recently, was not available.

This is the premise behind all Earth Observing Satellites that are operational today. Images of the Earth are acquired by using an active energy source, (radar beam) or solar illumination from the visible and IR bands , or emission from the Earth (thermal bands). Scientists are able to study and analyze the processes on the Earth by understanding the physical properties of the surface.

There are two principle sensors which are used to study the Earth; passive or active sensors. Passive sensors are merely recording the amount of energy being emitted by the Earth and reflecting solar radiation, whereas active sensors are sending an energy source to the Earth and measure it's response time back to the sensor.


Last Modified: Sun, Aug 24, 1996