A new microwave spectrometer for ground-based observations of water vapour

摘要: Abstract. We have developed a new, high time-resolution, microwave heterodyne spectrometer for observations of water vapour in the middle atmosphere. It measures rotational transition at 22.235 GHz vertical and horizontal polarisation. The two polarisations are averaged order to optimise signal-to-noise ratio. different separate, but identical, signal chains consisting 22 cooled HEMT amplifier, second, warm, booster an IF stage Chirp Transform Spectrometer (CTS) backend. Continuous calibration with internal loads kept temperatures close observed atmosphere, wobbling optical table reduce standing waves path low receiver temperature ensures time resolution magnitude better than what has been achieved by earlier instruments. error sources retrieved spectrum discussed data is compared validated against EOS-MLS on NASA Aura satellite. profiles found be good agreement each other.