Airborne Spectroscopic Static Temperature Sensor

We will develop a high speed, high accuracy method to measure the static air temperature outside an airplane using open path, infrared spectroscopy. We will project a laser beam outside the aircraft and reflect it back to its source obtaining the infrared spectrum outside the aircraft. The laser will primarily probe undisturbed air which has not yet been affected by the aircraft. Static air temperature will be extracted from the spectrum from the relative intensity of two spectral lines with dramatically different temperature dependence. This provides a static temperature measurement which is dramatically better than existing methods. Phase I results show that we will improve measurement precision by a factor of 100 (to 5 mK) and time resolution by a factor of 100 (to 10 ms). We are hopeful that accuracy can also be improved by a factor of 5 (to 0.1 K). Temperature data are critical to improved weather and radiative forcing prediction. Of particular interest are Ice Super Saturated Regions (ISSRs) that occur in the upper troposphere. ISSRs are regions where contrails form when aircraft fly though them. Contrails are a key environmental impact of commercial aviation, representing roughly 2/3 of the radiative impact of the commercial fleet. Better temperature data can address these concerns. Current temperature measurements are not sufficiently accurate. During Phase II we will execute a detailed design for a prototype instrument. The instrument will consist of two sub-units: 1) a small chassis containing the electronic control and data acquisition systems and 2) a compact optical system containing the laser and the infrared detector ready to be mounted in an aircraft pylon. The prototype instrument will be constructed and tested extensively at Aerodyne. We will also pursue opportunities to flight test the prototype during Phase II. Our first market will be the aviation research community. There may also be a larger market in commercial aviation.