Just heard this story on "Talk of the Nation." NASA is embarking on a new mission, the Orbiting Carbon Observatory to monitor atmospheric carbon dioxide. A new sensor will be launched in 2008 and will have a few interesting features. First, this sensor contains three separate spectrometers, each capturing a different band. Second, the sensor will detect three distinct bands in the near infrared. Two of these bands are carbon dioxide bands, which measure the wavelength ranges that are absorbed by carbon dioxide, but little else on the earth's surface. As far as I know, this may be the first sensor designed to directly detect atmospheric gases.