Measurements of ozone in the MOZAIC program are taken every four seconds from take-off to landing. Based on the dual-beam UV absorption principle (Model 49-103, Thermo Environment Instruments, USA), the measurement accuracy is estimated at ±[2 ppbv + 2%] (Marenco et al., 1998 ; Thouret et al., 1998). From the beginning of the program in 1994, the measurement quality control procedures have remained unchanged to ensure that long-term series are free of instrumental artifacts. Instruments are calibrated in the laboratory before and after the flight periods, whose duration is generally 12 months. The laboratory calibration is performed with a reference analyser which is periodically cross-checked with a primary standard at the National Institute of Standards and Technology in France. Additionally, each intrument’s zero and calibration factor are regularly checked in-flight, using a built-in ozone generator.

References:

Marenco, A., V. Thouret, P. Nédélec, H. Smit, M. Helten, D. Kley, F. Karcher, P. Simon, K. Law, J. Pyle, G. Poschmann, R. Von Wrede, C. Hume and T. Cook, Measurement of ozone and water vapour by Airbus in-service aircraft: the MOZAIC airborne program, An overview, J. Geophys. Res., 103, 25631-25642, 1998. 

Thouret, V., A. Marenco, J. A. Logan, P. Nédélec, and C. Grouhel, Comparisons of ozone measurements from the MOZAIC airborne program and the ozone sounding network at eight locations, J. Geophys. Res., 103, 25,695-25,720, 1998.