Scanning filter photometer for the measurement of atmospheric NO2 and O3

The optical theory and instrumental requirements of a scanning filter photometer are described. Stratospheric trace gases and how they affect the ozone content of the atmosphere by introduction of antropogenically originated species NOx, ClOx, are outlined. It is shown that these species exist at stratospheric heights and their vertical distribution is chemically active. Measurement of causative changes by measuring the meridional distribution of two of the key trace species in the atmosphere, NO2 and O3 was undertaken. It is found that spectroscopic techniques are practical for NO2. A scanning filter photometer was developed in which the bandpasses of interference filters are varied by varying the effective angle of incidence of the solar beam. Such a technique overcomes the disadvantages of working at fixed frequencies.