A 280m open-path DOAS instrument was constructed. A folded-path configuration employing retroreflectors was chosen for advantages in sensitivity and convenience in instrument alignment and housing. An annular illumination single-telescope transceiver was used to reduce cost and system complexity. Data gathering was performed during March, April, and May of 2004. Calibration gases were unavailable, thus the instrument was calibrated with the OPSIS system (a commercial DOAS instrument located near the experiment). Results showed good agreement between the two instruments. The detection limit of the prototype instrument was estimated to be 1.4, 10, and 9 ppb for SO2, NO2, and O3 respectively.
[Presented at the Samahang Pisika ng Pilipinas (SPP) Congress, 2004.]