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.
VLA stereoscopy of solar active regions. 2: Altitude, relative motion, and center-to-limb darkening of 20 centimeter emission
A newly developed method of stereoscopic correlation is applied to solar radio maps at a wavelength of 20 cm. On the basis of stereoscopic correlations between radio maps obtained on 6 different days we establish the presence of 66 radio source components associated with 22 active regions. We find the following statistical results for active region source structures at 20 cm: 1. The observed lifetime is consistent with an exponential distribution having an e-folding time scale of greater than 18 days. 2. The average altitude of 20 cm sources is 25 +/- 15 Mm; 90% of the sources are found in heights less than 40 Mm. 3. The average diameter of discrete source structures is 48 +/- 15 Mm, implying a vertical/horizontal aspect ratio of q(sub A) approx. = 0.5. 4. No significant source motion has been found with respect to the standard differential rotation rate of Omega = 13.45 deg - ((3 deg (sin(exp 2)B)). 5. We find a statistical limb darkening, which can be described by the relation (T(sub B)(alpha))/T(sub B)(0)) = 0.4 + ((0.6(cos(exp 2) alpha)) for sources with T(sub B) greater than 0.5 MK. 6. The degree of source polarization is 15% +/- 10% and is independent of source location. 7. Bright sources (greater than or approximately equal to 0.5 MK), or equivalently, long-lived sources (greater than or approximately equal to 5 days) show a systematic variation of their altitude as function of the center-limb distance.