Focused Microwave Technique for Probing the Atmosphere at 60-200 km Heights

A system for remote optical diagnostics of the atmosphere/ionosphere at heights 60-200 km is proposed. The method relies on excited-ionized N2 and N2+ molecules by electron impact during microwave pulses injected from focused ground-based transmitter. A 32 GHz gyrotron was developed at the Associate Plasma Laboratory of INPE-Brazil to this purpose. The gyrotron creates energetic electrons in the ionosphere, which excite-ionize N2 molecules to higher energy levels. These excited molecules become targets for a laser ranging system by resonantly absorbing and reradiating light at specific wavelengths. The laser return signal intensity gives information on the density of the ionospheric species under consideration, and its delay gives the height. Also, the reradiated light is detected by a ground-based photometer. A study of atmospheric species for ranging was performed, and the most suitable species were found to be N2 and N2+.