Development and testing of several lunar photometer prototypes and the new Triple (Sun-Lunar-Sky) CE318-T photometer

Development and testing of several lunar-photometer prototypes (i.e. modified CE318-N and CE318-U) capable of measuring aerosols and column water vapour during the night period, has been performed at IZO in collaboration with Cimel Electronique . The final version, the CE318-T, is able to perform daytime and nighttime photometric measurements using the sun and the moon as light source. This new device permits a complete cycle of diurnal aerosol and water vapour measurements valuable to enhance atmospheric monitoring.

Two new methodologies to transfer the calibration from a reference instrument using only daytime measurements (Sun Ratio and Sun-Moon gain factor techniques) have been developed and evaluated. These methods reduce the previous complexities inherent to nocturnal calibration. A quantitative estimation of CE318-T aerosol optical depth uncertainty by means of error propagation theory during daytime and night period has been assessed. A subsequent performance evaluation including CE318-T and collocated measurements from independent reference instruments has served to assess the CE318-T performance, day and night, as well as to confirm its estimated uncertainty. The CE318-T has been recently adopted by NASA AErosol RObotic NETwork (AERONET) as the new standard instrument of the network.

Figure 1.- The CE318-T photometer tracking the moon at IZO.