Experimental underground facility to evaluate remote sensing instruments

摘要

To carry out metrological tests on the automatic devices used in air quality monitoring networks, INERIS follows a standard text. In order to apply it, the instruments have been fed with reference mixtures of gases in several reproducible concentrations. Compliance with this requirement is quite easy to obtain, in the case of conventional techniques, but the problems remain with optical remote sensing instruments. The difficulties can be solved by using the Beer-Lambert law indicating that the product of the concentration by the distance is a constant value. To implement this optical law, INERIS uses a system with a two meters glass cell with quartz windows inserted in the instrument beam and fed dynamically with known concentrations of reference mixtures of gases. The test-bench facility is set up in a tunnel 90 meters long in INERIS. Tests on SO$-2$/, NO$-2$/ and O$-3$/ were carried out in 1997 on two types of DOAS systems set up in parallel: an OPSIS system and an Environment SA SANOA system. The following features were tested: the detection limit, the linearity and the drift. The tests results on the response of the two types of instruments are in agreement with the results obtained by the ERLAP at the Joint Research Center in Ispra.