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M. W. Bushroe, M. G. Tomasko, L. R. Doose, E. McFarlane, G. M. Prout, M. J. Pringle, B. Rizk, C. See (Univ. of Arizona)
The DISR instrument on the Huygens Probe includes a three-frame imager, upward and downward-looking visible and near-infrared spectrometers, a solar aureole camera having two spectral channels in two orthogonal directions of linear polarization, upward and downward-looking near-ultraviolet photometers, a sun sensing system for determining of the azimuth of the camera axis relative to the direction to the sun, and a lamp for illuminating the ground at low altitudes to permit spectrally continuous measurements of the reflectivity of the surface of Titan.
In order to prepare for the reduction, display, and interpretation of the wide variety of data planned from the Titan entry, we have begun a program to collect similar data on the Earth using a prototype DISR instrument. Observations have been made in a series of helicopter flights over southern Arizona, fixed platform tests on the building rooftop, and tipping, tilting, rotating tests on the building roof top, nearby hillsides, and mountain top fire-tower. Samples of imaging data, spectra of direct and diffuse solar flux, reflection spectra of different terrains, and solar aureole measurements will be shown. In addition, examples will be presented of how the terrestrial observations are being used to practice achieving the four main science objects for Titan observations of: 1) Surface topography and composition, 2) Atmospheric composition, 3) Solar energy absorption and net thermal balance, and 4) Aerosol size(s), abundance, and optical properties.