This work demonstrates the indoor SI-traceable calibration of a transmissometer with a 75-m baseline for the measurement of visibility in MOR (Meteorological Optical Range). The calibration is performed using a set of neutral density (ND) filters (OD 0.1-2.5) and a set of high-transmission quartz glass plates (a bare quartz glass plate and antireflective-coated quartz glass plates), the collection consisting of 20 artifacts in total. The luminous transmittance values of the reference artifacts had been calibrated traceable to the KRISS spectral transmittance scale, which ranges from 0.2 % to 99.5 %. The transmissometer to be calibrated typically consists of a loosely collimated light source based on a white LED (CCT ~5000 K) and a luminous intensity detector with a CIE 1924 V(λ ) spectral response. As a result of calibration, we obtained the MOR error and its uncertainty for the transmissometer in 20 m -40 km of MOR. Based on the results, we investigated the applicability of the calibration method and the conformity of the transmissometer to the ICAO's (International Civil Aviation Organization) accuracy requirement for meteorological visibility measurement. We expect that this work will establish the standard procedure for the SI-traceable calibration of a transmissometer.

To improve LII as a quantitative tool for extraction of soot properties, the models describing the heat and mass transfer between the particles and the surrounding gas must be tested against well-characterized experiments. In this work we have made a detailed investigation in which experimental results have been compared with simulated ones in two different configurations; backward-LII and 90º-LII. Although the results show a qualitatively good agreement, it is realized that an improved physical description is needed for the LII signal behavior.