An inexpensive net radiometer for multipoint spatial surveys

Abstract

The article describes an inexpensive net radiometer intended for multipoint spatial surveys. The radiometer employs plane polyethylene windows instead of domes. The use of plane windows eliminates the need for pressurizing and, because of the lesser air volume enclosed, reduces the potential for internal condensation. However, it also gives the radiometers an effective angle of view and a cosine response that both differ from those of domed instruments, and it may enhance effects of temperature differences between the upper and lower polyethylene shields in calm conditions. The new radiometer is easy to manufacture with uniform characteristics using readily available materials. Forty-four net radiometers were built, laboratory and field tested, and used with good success both under winter and summer conditions. Their sensitivity is 8.166 μV/W/sq m±7% in the thermal and 7.814 μV/W/sq m± 4% in the solar spectrum according to the laboratory tests, thus exhibiting a 4.5% greater sensitivity in the long than in the short wavelengths.