A novel method for remote optical diagnostics of the atmosphere at heights 30--60 km is proposed. The method relies on exciting atoms and molecules of minority species by electron impact during and following an ionizing microwave pulse injected from a focused ground-based transmitter. Free electrons produced in the breakdown region are the exciting agents for the atmospheric target molecules. The mixing ratio of the minority species can then be measured by either detecting the direct emission from allowed transitions or by utilizing lidar techniques to measure the excitation level of metastable states. Computer simulations of the intensity of the expected emission, based on kinetic theory of air breakdown, are presented. It is shown that mixing ratios below particle per trillion can be detected using microwave heaters with state of the art effective radiation power and modern detection technology. ¿ American Geophysical Union 1994