An architecture program for the robotic exploration of Venus
To date, most space exploration has focused on the solar system beyond Earth's orbit while the inner solar system between Earth and the Sun has received only limited attention. In this region, Venus, with a similar size and mass to Earth but with a very different environment, is probably the most interesting body. The most notable feature of Venus is the extreme runaway greenhouse effect. This phenomenon is considered a potential fate for the Earth in the future. Exploring Venus could help mitigate this threat. However, the environment of Venus is sufficiently challenging as to preclude the possibility of physical human presence for the foreseeable future. Consequently, robot-mediated exploration is required
The VEVA Mission; exploration of Venus volcanoes and atmosphere
Greeley, E. R. Stofan, M. H. Acuna, A. Chutjian, D. Crisp, J. Cutts, B. Fegley, J. Guest, J. W. Head, K. Klaasen, J. P. Mustard, D. Senske, Center for Earth and Planetary Studies, Smithsonian Institution, Washington, DC 20560, campbell@ceps.nasm.edu, Arizona State University, Tempe, AZ 85287, University College London, London NW8 9RE, UK, Goddard Space Flight Center, Greenbelt, MD 20771, Jet Propulsion Lab, Pasadena, CA 91109, Washington University, St. Louis, MO 63130, Brown University, Providence, RI 02912.
Probing Venus's cloud structure with Galileo NIMS
The spectral image cubes obtained by the Near-Infrared Mapping Spectrometer (NIMS) on Galileo as it flew by Venus have been analyzed to constrain the vertical structure of the clouds, the nature of the aerosol particles, and the location and particle properties of the opacity variations responsible for high contrast features observed in the near-infrared windows at 1.7 and 2.3 μm. A radiative transfer program was used to simulate mid-latitude curves of limb darkening at 3.7 μm. Best-fit models to these curves demonstrate that the upper clouds are dominated by mode 2 particles (r = 1.0 μm), with a contribution of ≈15% of opacity from mode 1 particles (r = 0.3 μm). The low-latitude upper cloud is well represented by a dual scale-height model, with a particle scale height of ≈1 km from an altitude of 61–63 km, and a scale height of ≈ 6 km above this, up to the level where τ = 1 at approximately 71 km. This model also successfully simulates limb-darkening curves at 11.5 μm from the Pioneer Venus Orbiter Infrared Radiometer. Successful simulations of correlation plots of 1.7 vs 2.3 μm intensities reveal that mode 3 particles (r = 3.65 μm) represent the dominant source of opacity in the lower and middle clouds, and that variation in total cloud opacity reflects chiefly the addition and removal of mode 3 particles near the cloud base. We find that the full spectrum of brightnesses at 1.7 and 2.3 μm implies that the total cloud optical depth varies from ≈ 25 to ≈ 40.