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Microwave Remote Sensing


The GBMS (Ground-Based Millimeter-wave Spectroscopy) is a remote sensing technique to estimate the middle atmospheric vertical distribution of several chemical species (as for example O3, N2O and CO) by measuring their rotational emission lines. The measurement technique employs a superconducting mixer (SIS) cooled to 4 K that downconverts the atmospheric signal observed at 200-300 GHz to a signal that can be easily amplified at the intermediate frequency of 1.4 GHz. In our case, the GBMS measures emission spectra with a 600 MHz window tunable between 230 and 280 GHz, and with a 65 kHz resolution. The shape of each spectral line depends strongly on the chemical species concentration as a function of altitude. Vertical profiles of species concentration can therefore be determined by “inverting” the measured line employing physical models that describe the physical status of the middle atmosphere. In particular, assuming an average pressure line broadening of about 3 MHz/mbar, the GBMS can obtain vertical profiles of the observed compounds between 17 and 75 km altitude.

Thule High Arctic Atmospheric Observatory (THAAO)


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