Phaethon: A System for the Validation of Satellite Derived Atmospheric Columns of Trace Gases
Phaethon is a system for the retrieval of column densities of various atmospheric gases from the ground by applying the technique of Differential Optical Absorption Spectroscopy on direct sun and sky radiance spectral measurements. The system comprises a spectrograph with a CCD detector operating in the wavelength range 300–650 nm, the entrance optics with a field of view of 1°, equipped with a filter wheel, a temperature stabilization unit, and a solar tracker. The Phaethon system was validated against a MAX-DOAS system during a campaign at the High Altitude Research Station Jungfraujoch. The comparison of differential slant column densities derived from off-axis measurements showed an average agreement of 5–10% (±5%) depending on the viewing angle for NO2, and 15–25% for O4 (±2% for viewing angles <8°). Following the validation of Phaethon, direct solar irradiance and sky radiance spectral measurements are regularly performed at Thessaloniki, Greece, to derive atmospheric columns of various trace gases. The retrieved atmospheric columns of total and tropospheric NO2 were compared to GOME-2 products revealing large discrepancies which are attributed to the large spatial variability of NO2 due to the localized air pollution sources over the area.
KeywordsAerosol Optical Depth Total Ozone Solar Zenith Angle Atmospheric Column Differential Optical Absorption Spectroscopy
This project was funded under the Greek Industry Incentive Scheme (ESA-Greek Task Force), ESA Contract No. 22286/09/NL/CBI. The authors would like to thank M. van Roozendael, C. Fayt, G. Pinardi, for their substantial contribution in the validation of Phaethon and for providing the QDOAS algorithm. Also authors would like to thank D. Loyola for providing the GOME-2 data.
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