Techniques of ground-based remote sensing of the ozone layer by millimeter-wave heterodyne spectroscopy

MM-wave heterodyne spectroscopy is successfully used for measuring of the atmospheric ozone at altitudes from about 15 to 80 km. Remote sensing of trace gases, including ozone at MM waves has a number of obvious advantages. The required performance of a ground-based instrument for ozone observations at wavelength of 2 mm has bene determined using results of computer simulations. Main features of the Lebedev Physics Institute heterodyne radio spectrometer for 142.2 GHz ozone spectral line measurements are described, and key parts of the spectrometer receiver, such as input optics and low- noise Schottky diode mixer, are considered in greater detail. The receiver and the mixer have been tested throughout the 22- mm band at both room and liquid nitrogen temperatures and main results of the tests are presented. Blackbody cold loads have been used in the calibration/observation procedure, with special attention paid to accurately measuring their brightness temperatures. Some results of ozone observations for various atmosphere states are presented to demonstrate possibilities of ground-based MM-wave heterodyne spectroscopy.