The development of the SYMOCS instruments and the spectral analysis.

Since 1995, Norwegian Institute for Air Research (NILU) has measured the stratospheric compounds O3, NO2, BrO and OClO with a ground-based spectrometer that measures the scattered light from the zenith sky. The instrument system called SYMOCS (SYstem for MOnitoring Compounds in the Stratosphere), was developed at NILU. During 1998 a similar spectrometer system was developed in order to optimise the measurements of the four compounds. The two instrument systems are called SYMOCS-VIS (O3 and NO2) and SYMOCS-UV (BrO and OClO). This report describes the development and characterisation of the two instruments as well as the spectral analysis and retrieval of the compounds.