SOLAR-SYSTEM OBSERVATIONS BY THE WISCONSIN ULTRAVIOLET PHOTOPOLARIMETER EXPERIMENT .1. THE FIRST ULTRAVIOLET LINEAR SPECTROPOLARIMETRY OF MARS

The first ultraviolet (UV) linear spectropolarimetry of Mars using the Wisconsin Ultraviolet PhotoPolarimeter Experiment (WUPPE) was obtaine d on 1995 March 12 at a phase angle of 21.7 degrees. A ground-based su pport observation was taken within 5 h, providing a total spectral cov erage of 2100-10 200 Angstrom. The plane of polarization changes by 90 degrees at 4600 Angstrom. The UV polarization increases with decreasi ng wavelength, due to atmospheric scattering. A plane parallel, optica lly thin; atmosphere is used to model the polarization data, from whic h the optical depth of the atmosphere is derived. Assuming a pure CO2 atmosphere a total pressure of 6 mbar is obtained. The Lambert albedo of the surface is obtained in the wavelength range of 2100-3100 Angstr om. (C) 1997 American Astronomical Society.