Solar Limb Shape, Radius, and Oscillation Studies Using SoHO/MDI Jeffrey R. Kuhn University of Hawaii Above our atmosphere the solar limb is a sharp spatial fiducial for detecting the effects of solar oscillations, the gravitational quadrupole (and higher spatial moments), and solar radius changes. We recently showed that the photometric and astrometric accuracy that is possible from MDI image data is qualitatively superior to ground-based measurements -- solar limb shape changes on timescales of minutes to months and at spatial scales of microarcseconds to milliarcseconds were detected. This proposal describes a program to expand and explore the astrometric capabilities of the SoHO/MDI experiemnt. We expect to achieve very sensitive limits or detections of g-modes and possible solar radius changes, and to derive new insight into the deep solar interior changes that occur during the course of the solar cycle.