SurVenTIS - Studying the surface composition on a regional scale with high spatial resolution

Kurzfassung

The M channel of VIRTIS will allow the first systematic mapping of the surface and of the near-surface atmosphere of Venus in the near infrared wavelengths range. This will be done using the atmospheric windows located at 1.10, 1.18 µm and if possible additionally using the window at 1.02 µm (Wattson and Rothman 1986, Kamp et al. 1988, Moroz 2002). The latter is unfortunately right at the low end of the wavelength range of the IR channel and at the upper end of the VIS channel. Therefore, the usability of this window is unclear until first data from Venus are obtained. The atmospheric windows will allow measuring the thermal emission of the surface as was demonstrated by Galileo/NIMS (Carlson et al. 1991) and Cassini/VIMS (Baines et al. 2000). Based on these data three main science tasks for the surface analysis will be pursued: Classification of the surface composition, study the interaction between low atmosphere and surface, and detect active volcanic structures on the surface. Based on the thermal emission measured in the atmospheric windows and the estimate for the surface temperature the emissivity of the surface can be derived for each of the wavelengths. While these windows have a relatively high transmittance of 40-95%, the observations are still complicated by the cloud deck. Multiple reflections between the surface and the clouds tend to wash out essentially the contrast between high albedo and low albedo parts of the spectrum. Furthermore the scattering in the clouds decrease the achievable resolution. Based on modeling by Hashimoto et al. (2003) and Moroz (2002) we can expected to have a FWHM of 50-100km from orbit. If we place a thermal imager on a decent probe we can dramatically increase the spatial resolution and the achievable signal. We will briefly discuss the idea of SurVenTIS (Surface of Venus Thermal Imaging System) an imager with 6 geological filters. SurVenTIS would allow studying the surface composition at a regional scale in great details. Depending on the mission profile a surveyor of geological interesting regions is possible.