Self-calibrating Balloon-Borne Methane Gas Sensor

The release of greenhouse gases to the atmosphere through the burning of fossil fuels and other anthropogenic sources is considered to be the major cause of global warming, with potentially damaging economic and environmental effects worldwide. The sources and sinks of these gases and the interactions between the troposphere and stratosphere are needed to understand global warming and help devise strategies to minimize its effects. In situ measurements of greenhouse gases have been restricted to airplane or large balloon-gondola platforms, due to the size, weight, and power requirements of current instrumentation. We propose to overcome this limitation with a fully self-calibrating, low mass greenhouse gas sensor suitable for more frequent, widespread measurement campaigns using smaller, inexpensive balloon sondes. A lightweight, inexpensive, stand-alone methane sensor suitable for balloon sonde measurements will be developed. This sensor uses a novel self-calibration method to achieve the high precision of the much larger and expensive instruments used on current airborne platforms, but will operate on a small meteorological balloon. The Phase II result of this program will be a sensor capable of measuring methane with high precision using small, inexpensive balloon sondes without the need for highly trained personnel. All of the research objectives for Phase I were successfully met. The most critical issues were determining the most effective laser delivery mode and to compare two detection methods for optimum precision, accuracy and ease of use in a balloon environment. Based on these key factors, a detailed preliminary design, including expected performance specifications, was developed. In Phase II a prototype sensor will be constructed, tested and flown using meteorological balloons. This instrument will operate autonomously and be self-calibrating. Analysis methods will be developed, tested, and refined. Commercial Applications and Other Benefits: In addition to research instruments for atmospheric measurements, low cost, portable gas sensors have applications in such areas as environmental monitoring, gas leak sensing of pipelines, fire detectors for commercial and military aircraft, and process control sensors for energy and chemical production industries.