Ionospheric RF lidar

A new diagnostic consisting of a high-power RF or microwave transmitter and a ground-based lidar system is proposed for probing the ionosphere at heights of 80-200 km. The high-power transmitter creates energetic electrons in the ionosphere, which excite molecules to higher energy levels. These excited molecules become targets for a laser ranging system by resonantly absorbing and reradiating light at specific wavelengths. A laser pulse tuned to a specific transition wavelength is fired from a ground-based laser, and the reradiated light is detected by a ground-based light collector. A study of atmospheric species for ranging was performed, and the most suitable species were found to be N2 and N2(+). A laser whose output is matched exactly to the vibrational-rotational spectrum of ionospheric N2 is proposed as the lidar master oscillator instead of a tunable due laser. 13 refs