O during two airborne polar stratospheric campaigns in January and March 1997. These species were detected using integration periods of 1 s with a precision of ±2%(3σ) and a calibration accuracy of ±2.8% during a total of 11 measurement flights up to a maximum altitude of 12.5 km. More recently all three channels have been operated simultaneously for CO, CH4, and N2O with comparable results.