As radio waves travel through our Galaxy they are distorted by the inhomogeneous plasma in interstellar space. This creates a "seeing" problem for radio astronomers, comparable to atmospheric seeing for optical astronomers. The source is blurred, pulses are broadened, and constant sources appear to fluctuate (scintillate). The scintillations have to be recognized and separated from fluctuations which are intrinsic to the astronomical source. At the same time the scintillations provide a unique probe of the turbulence in the ionized interstellar medium. Drs. Barney Rickett and William Coles, at the University of California at San Diego, have considerable experience in the theory and observation of such phenomena. With this award they will refine the current understanding of the spatial and spectral distribution of the interstellar plasma, and they will apply the results to the study of the ionized interstellar medium and to extremely compact extragalactic radio sources, including the afterglows from Gamma-Ray Burst sources. This award is funded through the Galactic Astronomy Program. ***
