Mobile Instruments Measure Atmospheric Pollutants
- Sunday, 01 November 2009
Originating Technology/NASA Contribution
As a part of NASA’s active research of the Earth’s atmosphere, which has included missions such as the Atmospheric Laboratory of Applications and Science (ATLAS, launched in 1992) and the Total Ozone Mapping Spectrometer (TOMS, launched on the Earth Probe satellite in 1996), the Agency also performs ground-based air pollution research. The ability to measure trace amounts of airborne pollutants precisely and quickly is important for determining natural patterns and human effects on global warming and air pollution, but until recent advances in field-grade spectroscopic instrumentation, this rapid, accurate data collection was limited and extremely difficult.
In order to understand causes of climate change and airborne pollution, NASA has supported the development of compact, low power, rapid response instruments operating in the mid-infrared “molecular fingerprint” portion of the electromagnetic spectrum. These instruments, which measure atmospheric trace gasses and airborne particles, can be deployed in mobile laboratories—customized ground vehicles, typically—to map distributions of pollutants in real time. The instruments must be rugged enough to operate rapidly and accurately, despite frequent jostling that can misalign, damage, or disconnect sensitive components. By measuring quickly while moving through an environment, a mobile laboratory can correlate data and geographic points, revealing patterns in the environment’s pollutants. Rapid pollutant measurements also enable direct determination of pollutant sources and sinks (mechanisms that remove greenhouse gasses and pollutants), providing information critical to understanding and managing atmospheric greenhouse gas and air pollutant concentrations.
With a Small Business Innovation Research (SBIR) contract from Ames Research Center in 1985, Aerodyne Research Inc. (ARI), based in Billerica, Massachusetts, began developing its Tunable Infrared Laser Differential Absorption Spectrometer (TILDAS) instruments for measuring stratospheric ozone depletion and greenhouse gasses. Additional SBIR contracts followed from both Ames and Glenn Research Center to develop TILDAS for measuring ambient pollutant concentrations and pollutant source fluxes.
ARI has also collaborated with the Agency’s Office of Earth Sciences, now part of the Science Mission Directorate, to develop innovative mobile laboratory capabilities to characterize and analyze urban air pollution. TILDAS instruments have been used in ARI’s mobile laboratories to map urban greenhouse gas and air pollutant distributions, starting with Agency-sponsored field measurements in Boston and Cambridge, Massachusetts, and in Manchester, New Hampshire in the 1990s. Later, field studies (sponsored in part by Glenn and Langley Research Center) included mobile studies of exhaust emissions from city buses in New York, traffic in Mexico City, and commercial aircraft during taxi, take-off, and landing operations at airports in Oakland, California, and Atlanta. According to ARI’s president, Charles Kolb, these projects enabled ARI to improve the company’s advanced instrumentation for mobile laboratories while providing valuable data for air quality managers working to improve urban air pollution.
In 2002, ARI introduced a line of thermoelectrically cooled quantum cascade (QC) TILDAS instruments, which are much smaller, more highly automated, and more robust than earlier lead-salt diode laser systems. ARI developed QC-TILDAS to detect a range of more than 15 of the most important greenhouse gasses and air pollutants—including carbon dioxide, nitrogen dioxide, and methane—at sub-parts-per-billion concentrations. Depending on laser selection and tuning range, each laser can quantify one to three trace gasses. The system consists of the tunable laser, infrared detectors, power electronics, a microcomputer with integrated control and data analysis software, and an astigmatic multiple pass absorption cell.