Calibrated remote measurement of NO2 using the differential-absorption backscatter technique

A tunable dye laser, operating between 4400 and 4500 Å, was used to monitor NO2 concentrations in a sample chamber 365 m away. The atmosphere in front of and behind the chamber acted as a distributed reflector to send laser light back through the chamber to a receiver near the laser. The laser measurements agreed well with in situ measurements. A single pair of laser pulses allowed the determination of NO2 concentrations with an uncertainty equivalent to 0.05 km ppm.