9419235 Tape This project is an experimental and theoretical study of ice crystals in the antarctic atmosphere and the halos that they produce. For reasons that are not currently known, the antarctic interior experiences more frequent and better developed halos than any other location on Earth. The objectives of the project are to observe natural halos at South Pole Station and to sample ice crystals in order to validate computer models of light refraction and reflection in ice crystals. Such models have the potential for the remote sensing of atmospheric conditions. Controlled experiments, such as seeding the atmosphere with dry ice, will produce artificially generated, but simple and well-formed single- species crystals. The project provides a unique mechanism for examining the crystal growth and evolution process in the natural atmosphere; the observation of halos through polarizing filters will also allow an examination of the atmospheric ice crystal orientation, shape, and size. It will advance our understanding of the reasons for the growth of well-formed ice crystals, which is a characteristic of the antarctic atmosphere, but is not generally observed elsewhere. ***
