A major result of the IRAS mission was that the infrared spectral energy distributions (SEDs) of many young stars can be explained by protoplanetary disks. Recent images from the repaired Hubble Space Telescope have now directly verified the presence of disks in a few cases. One of the most important of these is the nearby object HH 30, where an optically thick circumstellar absorption disk, 450 AU in diameter, is seen nearly edge-on. HH 30 is now the best-resolved (7 AU per pixel) astrophysical accretion disk system of any type, and the first where the disk's vertical structure is clearly visible. Model fitting of the HST images constrains the disk density and temperature distributions to a family of solutions corresponding to a wide range of possible infrared spectral energy distributions. Obtaining new SED measurements is therefore critically important to a full understanding of the disk's internal structure, for determining the source luminosity, and for placing HH 30 in proper context with other objects already studied by ISO and IRAS. We propose ISOCAM and ISOPHOT observations to measure the spectral energy distribution of HH 30 between 5-90 microns. These data will be combined with the unique geometrical information available to firmly establish the relationship between temperature and vertical thickness for a young stellar object disk. The results should provide unique insights into protoplanetary environments, and a strong test of accretion disk theories which are widely applied in astrophysics.