Development of a 22 GHz ground-based spectrometer for middle atmospheric water vapour monitoring

The water Vapour Emission SPectrometer for Antarctica at 22 GHz (VESPA-22) has been designed for long-term middle atmospheric climate change monitoring and satellite data validation. It observes the water vapour spectral line at 22.235 GHz using the balanced beam-switching technique. The receiver antenna has been characterized, showing an HPBW of 3.5° and a sidelobe level 40 dB below the main lobe. The receiver front-end has a total gain of 105 dB and a LNA noise temperature of 125 K. A FFT spectrometer (bandwidth 1 GHz, resolution 63 kHz) will be used as back-end, allowing the retrieval of H2O concentration profiles in the 20 to 80 km altitude range. The control I/O interface is based on reconfigurable hardware (USB-CPLD).