Passive Remote Sensing


The MAMAP2D-Light (M2DL) instrument was designed and built at the Institute of Environmental Physics in Bremen, Germany, to determine methane (CH4) and carbon dioxide (CO2) emissions from aircraft using solar absorption spectroscopy. M2DL captures sunlight reflected from the Earth’s surface in the spectral range from 1559 nm to 1690 nm with approximately 1 nm spectral resolution, about 120 m x 120 m spatial resolution, 3250 m ground track width (both at HALO flight altitude), and a signal-to-noise ratio of 300 – 600 depending on surface brightness and solar altitude.

The relative increase in CH4 or CO2 concentration in the atmosphere is determined from the recorded spectra using the method of absorption spectroscopy. Relative increases in CH4 or CO2 concentration in the atmosphere can be determined with a precision of about 0.2% – 0.4% of the background column. From the spatial change in concentrations, in combination with data on the meteorological conditions, information about the emissions of CH4 and CO2 sources will be determined.


The spectrometer of the Munich Aerosol Cloud Scanner (specMACS; Ewald et al, 2016) consists of two camera systems, both looking nadir, one in the visible/near-infrared (400 nm to 1000 nm), and another in the short-wave infrared (1000 nm to 2500 nm). The systems produce a spectrally resolved line image with 1312 pixels covering a 32.7º field of view in the visible/near infrared, and with 320 pixels covering a 35.5º field of view in the short-wave infrared.

In addition, specMACS features two polarization resolving 2D cameras to capture three components (I, Q, U) of the Stokes vector. Both subsystems were originally developed to retrieve cloud properties. During CoMet 2.0, their scope of application will be extended to provide spectral ground albedo and to spatially resolve point-sources of CH4.