Automatic recording transmissometer for atmospheric attenuation measurements at 0.9 μm wavelength

The design and performance of a double-ended transmissometer that accurately records the frequency and magnitude of atmospheric attenuation due to mists and fogs is described. Transmission data, covering a 50 dB dynamic range, is recorded automatically at five minute intervals on magnetic tape. The system is battery operated and capable of unattended operation for a period of one month. Results obtained, following the use of the equipment at an outdoor site for a year, are also presented.