Measuring method of the EM27/SUN spectrometer

MEASURING PRINCIPLE OF THE EM27/SUN SPECTROMETER

The Fourier spectrometer uses solar radiation to determine the atmospheric gas concentrations averaged along the visual beam. On the outside, the device carries an arrangement of motorized mirrors to follow the sun’s course in the sky.

The process uses the characteristic wavelength-dependent attenuation of solar radiation caused by the gas molecules. At its heart is a Fourier spectrometer that determines the brightness of the radiation as a function of the wavelength without performing color decomposition of the radiation with prism or diffraction grating. All parts of the signal are simultaneously captured by the targeted superposition of the incoming radiation waves, which amplify or weaken like water waves.

The following computer-based evaluation of the measured brightness as a function of wavelength provides the sought-after greenhouse gas quantities in the atmosphere.

Our technological civilization has significantly increased the content of the long-lived greenhouse gases carbon dioxide (CO2) and methane (CH4) in the atmosphere compared to pre-industrial times – the result is already a demonstrable warming of the earth’s climate!

The Earth absorbs energy in the form of sunlight and radiates long-wave thermal infrared radiation back into space.  The atmosphere has a major influence on this energy exchange:  While the main components of the atmosphere, nitrogen and oxygen, allow the thermal radiation to pass through unimpeded, greenhouse gases make the atmosphere impervious to this radiation and thus increase the temperature of the ground.  In order to be able to make more accurate predictions of the future development of the climate, it is crucial to better understand the sources and sinks of these greenhouse gases.

The method presented here allows the robust measurement of sources and sinks of greenhouse gases by detecting the resulting small deviations of greenhouse gases in the atmosphere.

FURTHER INFORMATION ON THE EM 27/SUN FOURIER SPECTROMETERS CAN BE FOUND IN THE FOLLOWING BROCHURE: