Passive Remote Sensing

During the last years, researchers at the Institute of Environmental Physics, University of Bremen, Germany, demonstrated that emissions of strong and localized emitters of CH₄ and CO₂ can be quantified independently using passive remote sensing of the atmospheric distributions of CH₄ and CO₂.

The current system – Methane Airborne Mapper (MAMAP) – is a 1-d (one measurement across track, continuous measurements along track, see figure) performing precise along track “mapping” of atmospheric CO₂ and CH₄ distributions around a strong emitting point source. With MAMAP (1-d) it has been demonstrated that emissions from strong and localized point sources like power plants (CO₂), coal mines (CH₄) and landfills (CH₄) can be determined quantitatively. Important error sources are related to the knowledge of changes in meteorological conditions (wind direction, wind speed, etc.) during the measurement duration of typically several hours. These error sources can be minimized with a 2-dimensional imaging spectrometer with similar single-pixel performance as MAMAP just by reducing the measurement time (1-d vs. 2-d). This allows reducing the detection limit and sensitivity to smaller point source emitters by approximately an order of magnitude compared to MAMAP.

The goal within AIRSPACE is therefore to build, test, and apply an airborne 2-d imaging greenhouse spectrometer (MAMAP2D) with a strong MAMAP heritage to demonstrate the advantage of 2-d GHG imaging for independent quantification of CO₂ and CH₄ point source emissions, and to develop the respective retrieving algorithms.

Not directly part of AIRSPACE, but closely related is the deployment of MAMAP (see right figure) during the CoMet campaign onboard the Cessna 207 operated by FU Berlin. This aircraft will perform coordinated flights with both other aircraft. The individual data sets from each instrument will be quality assured and merged for synergetic use.

The validation of current and upcoming greenhouse gas satellite missions will predominantly be guaranteed by means of the international TCCON network (Total Carbon Column Observing Network). In addition to the stationary TCCON spectrometers, mobile devices have been developed over the last few years. Those have the advantage of achieving both the required accuracies as well as mobility enabling their deployment in the field during dedicated campaigns. Within AIRSPACE, one of these mobile spectrometers (Bruker EM27/SUN, see figure above) will be operated at the campaign location in order to validate and reference the CO₂ und CH₄ columnar concentrations measured from the overpassing aircraft and satellites. The figure shows such a device during a recent deployment in the Upper Silesian Coal Basin (USCB).