講演者  : Nils Mueller
    Institute of Planetary Research, German Aerospace Center (DLR)
タイトル: Retrieval of Venus surface properties from Near-Infrared 
          spectrometrie with VIRTIS on Venus Express
日時    : 2007 年 6 月 28 日 (木)  16:00 - 17:00
場所    : 自然科学研究科３号館 6階セミナー室 (609)








  Venus is shrouded in an optically thick atmosphere that prevents direct
remote sensing of the surface short of millimeter wavelengths. Through
narrow spectral regions at 1.02, 1.10 and 1.18 micrometer, thermal emission
from the surface of Venus escapes into space, carrying with it information
about its source.



  Since orbit insertion in April 2006 VIRTIS on Venus Express is mapping this
radiation using nightside observations of Venus. While the atmospheric
windows show little absorption, the radiance from the surface is still
affected by scattering in the clouds. This modulates the surface signal due
to the variable optical thickness of the clouds.



  To retrieve information on the surface, the different contributions from
surface and atmosphere have to be separated. To achieve this the data is
inverted with a basic model of radiative transfer in the venusian
atmosphere.



  This approach allows to compare the spatial variation of the surface
brightness temperature with the surface temperature calculated from
altimetry data from the Magellan Radar Orbiter. This comparison allows an
estimate of the variability of surface composition.
The data gathered since begin of the mission suggests, that there is some
compositional variability that is correlated with distinct geological
features seen in the Magellan Synthetic Aperture Radar images.