Pyrgeometer MS-202 is designed to measure long-wave radiations beyond 3µm. A specially coated silicon dome transmits incident radiation which have a wavelength above 3µm by cutting off the shorter wavelengths of the sun spectrum. A radiative compensation circuit with a thermistor is integrated in the MS-202. This circuit is used for the sensor body temperature measurement or to measure Long wave downward radiation in the active mode. The analog output voltage of the detector is linear to the net radiation emitted by the atmosphere and ground. A thermistor dome temperature sensor is available as an option. Pt-100 temperature sensor for both the sensor body temperature and the dome temperature is also available as an option.