The results of interferometry experiments utilizing a Ku band synthetic aperture (imaging) radar flying repeat-pass trajectories are described. The radar is equipped with on-board differential GPS, which permits precise control and measurement of flight paths. Additional inertial sensors allow high-bandwidth motion compensation of the SAR images. Interferometric processing of flight data permitted formation of topographic images. However, due to the shallow grazing angles (10 degrees) and propagation through 40 km of atmosphere, phase anomalies were visible which were attributed to atmospheric granularity. This paper examines the phase disturbances visible in repeat-pass interferometric experiments and quantifies the phenomenon in relation to available sources on this subject. The line-of-sight path through the lower atmosphere is significantly longer than in previous satellite interferometric experiments. Data from a series of flights spanning late 1993 and early 1994 are presented, along with topographic radar imagery processed at 4 m resolution.