Dr. Gwinn will continue studies of interstellar scattering with very long baseline interferometry (VLBI). These studies probe the density fluctuations responsible for interstellar scattering, particularly their spatial spectrum, and the structures of the scattered sources. He will: (i) Further study scattering of Hydroxyl masers in the source W49N; (ii) Study scattering of the Vela pulsar; (iii) Attempt to resolve the emission region of the Vela pulsar at nanoarcsecond scales, using the scattering disk as a lens; (iv) Observe scattering from pulsars showing strong low frequency variability; and (v) Assess the effects of scattering on astrometric observations of the millisecond pulsar 1937-214. Observations of pulsars will make use of VLBI in the snapshot, or speckle, regime of scattering.
