Spectroscopic detection of aircraft wake gases

Using the technique of limiting information-metric scales, the potential of laser IR absorption spectroscopy for detecting small gas components of aircraft wake was quantitatively analyzed. Formulas for minimum distinguishable and minimum detectable gas concentrations were derived. Calculation was carried out for SO₂, NO, and NO₂ under typical conditions near the Boeing 707 aircraft engine nozzle at altitude H = 12.2 km. Alternative IR laser spectroscopy methods for detecting various gas components in the near wake were considered. Two possibilities to improve the concentration measurement sensitivity were analyzed: (i) a decrease in the background absorption of CO₂ and H₂O and (ii) an increase in the absorption cross section of detected gas.