Laser remote sensing of hydrazine, MMH, and UDMH using a differential-absorption CO2 lidar.

A dual mini-TEA CO(2) laser differential-absorption lidar system has been used to test the remote sensing of hydrazine, unsymmetrical dimethylhydrazine (UDMH), and monomethylhydrazine (MMH) in atmospheric conditions. Average concentrations of these compounds were measured using backscattered laser radiation from a target located at a range of 2.7 km. The experimental results indicate that average atmospheric concentration levels of the hydrazine compounds of the order of 40-100 ppb can be detected over ranges between 0.5 and 5 km. The level of concentration sensitivity over this interval was found to be limited primarily by atmospheric fluctuations. An investigation of the effect of these fluctuations on measurement uncertainties indicated that the fluctuations reduce the benefits of signal averaging over N pulses significantly below the expected square root of N improvement. It is also shown that uncertainties due to long-term atmospheric drifts can be effectively reduced through use of dual-laser lidar return ratios.