A device for measuring the intensity of electromagnetic radiation. Radiometers operate across the whole spectrum, but in the visual region they are usually termed photometers. Many Earth-resources satellites carry radiometers operating in the infrared and visual parts of the spectrum to produce false-colour maps of the planet showing, for example, crops, geological forms, and weather systems. Space probes carry radiometers to survey other Solar System bodies in similar fashion. At radio wavelengths, radiometers tend to be comparison devices, repeatedly comparing the signal from the object with that from an artificial source to improve their stability. See dicke radiometer.