A Study of Mesospheric Radar Scattering In this one year program of research, an explanation will be sought for the disagreement between motions inferred from the analysis of incoherent scatter and partial reflection radar data as measured during the Arecibo Initiative on the Dynamics of the Atmosphere, March through May, 1989 (AIDA '89). The principal data sources to be utilized come from the Arecibo observatory UHF incoherent scatter radar (ISR) observations, from the Utah State University imaging doppler interferometry (IDI) MF radar and from the Geospace Research meteor wind radar (MWR). The investigation will concentrate on the scattering mechanisms involved, which, at least in the case of the IDI, are as yet not fully understood. The IDI scattering points may originate from turbulent eddies in the mean flow, or they may be specular reflection from individual gravity wave fronts. To address this problem the investigators will rely heavily on the considerable body of knowledge available on the propagation of waves in turbulent media, and on an existing archive of "snapshots" of small scale motions at mesospheric - lower thermospheric altitudes as revealed by high resolution photography of rocket released chemical trails.