EM27/SUN 太阳辐射吸收光谱仪

SOLAR ABSORPTION SPECTROMETER

Measure the Greenhouse Gas Concentration throughout the Entire Atmosphere

The EM 27/SUN series spectrometers represent FT-IR remote sensing analyzers dedicated to atmospheric measurements. For these spectrometers, the sun serves as the light source, followed by a camera-based solar tracker. They quantify gases such as carbon dioxide and methane in the atmosphere by analyzing the absorption spectra of sunlight.

The EM 27/SUN provides a very compact and robust design, relatively low weight, and an intuitive user interface. They are highly portable and hence ideally suited for measurement campaigns in remote areas with little infrastructure. Combined with our high-resolution FT-IR spectrometer IFS 125HR and high-precision laser-based gas analyzer MGA series, we provide customers with a diverse range of complementary solutions for greenhouse gas (GHG) analysis and atmospheric research.

User Network

The EM 27/SUN is the standard instrument in the global network COCCON (COllaborative Carbon Column Observing Network). City-level and national-level networks consisting of several EM 27/SUN units are built to monitor changes in GHG concentrations across a given area.

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Camera-based Solar Tracker

Schematic drawing shows the solar tracker of the EM 27/SUN, which follows the movement of the sun.

When using the sun as a light source for atmospheric absorption spectroscopy, accurately tracking the sun is an important factor in minimizing errors in the retrieval of gas concentrations in the atmosphere.
The EM 27/SUN uses an innovative camera based feedback system to track the movement of the sun and couple the solar beam into the spectrometer. The CamTracker software evaluates the solar image on the detector in real-time to actively control the rotation of the tracking mirror and stage, ensuring the tracker follows the sun.

An important feature of this solar tracker is its ability to accurately track the sun even if there is a thin cloud layer or mist covering it.

Determine the GHG Emission Rate from a City

Multiple EM 27/SUN units can be positioned around a regional GHG source, such as a city, to deduce its GHG emission rate. This rate is determined by measuring the concentration difference of GHG between two EM 27/SUN units at different locations, combined with meteorological information such as the wind speed and a transport model.

Schematic drawing of the measurement setup with multiple EM 27/SUN to determine the GHG emission rate from a city. X_GHG: measured concentration of GHG, ΔX_GHG: difference between the X_GHG measured at the upper and down wind locations.

Such measurement campaigns have been carried out in several cities around the world. As an example, the Tokyo Campaign is shown in the video below.

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Examples of measurement campaigns of deploying multiple EM 27/SUN units around a city

St. Petersburg and Yekaterinburg (2019-2020)
Munich (2018)
Indianapolis (2016)
Tokyo (2016)
Paris (2015)
Berlin (2014)

Validation of Satellite Measurements

EM 27/SUN is very suitable for validating the measurement results of GHG monitoring satellites because both systems share a similar measurement geometry (i.e., measuring through the entire atmosphere).
Thanks to EM 27/SUN's high portability, its measurement campaigns for satellite validation can even be conducted in remote locations.

Locations (and the satellites to be validated) of some examples of such measurement campaigns are shown in the list below and on the map here. A series of campaigns for the validation of CH₄and CO products from the Sentinel-5 Precursor (S5P) mission can be found on this website.