Spectral and cross‐spectral signatures of lower mesospheric radar returns are investigated and modeled. Aspect sensitivity of radar echoes and the horizontal, vertical, and random components of atmospheric fluid velocity are estimated. Estimated random velocity magnitudes of ∼0.2 m/s during a specific lower mesospheric scattering event are smaller than corresponding Doppler spectral widths of ∼1 m/s. During the same event, aspect sensitivity variations as large as ∼10 dB/deg were observed. Higher mesospheric returns generally indicate stronger random velocity amplitudes and weaker aspect sensitivity variations. The extreme conditions encountered in the lower mesosphere can introduce systematic errors in wind and turbulence studies, but simple interferometric methods are suggested to cope with such problems. Data analysis in this paper includes first examples of the implementation of the recently introduced poststatistics steering (PSS) technique. A cross‐spectral model developed in the appendix should be suitable for the analysis of most middle atmospheric radar interferometer data. Copyright 1990 by the American Geophysical Union.