CONTOUR Comet

Not all space missions to comets have been as successful as Stardust and Deep Space 1. For example, NASA s CONTOUR (Comet Nucleus Tour), launched on July 3, 2002, was designed to rendezvous with and study Comet Encke on November 12, 2003, and Comet Schwassmann-Wachmann 3 on June 18, 2006. All contact was lost with CONTOUR on August 15, 2002, however, and the mission was canceled. 

When very high velocities are encountered, metal loss from erosion-corrosion can be general. T ically, however, erosion-corrosion produces localized metal loss in immediate proximity to the disrupted flow. Smooth, rolling, wavelike surface contours are often produced, or distinct, horseshoe-shaped depressions (Fig. 11.1) or comet tails... 

The classic signature of erosion-corrosion is the formation of horseshoeshaped depressions, comet tads, grooves, or sand dunelike surface contours oriented along the direction of fluid flow (Figs. 11.1,11.2,11.3,11.5, and 11.8). Occasionally, erosion-corrosion will produce smooth, almost featureless, surface contours (Fig. 11.15), although even in this case oriented metal loss often exists around the perimeter of the affected region. If erosion-corrosion has been recently active, affected surfaces will be free of accumulated deposits and corrosion products. 

Abstract. We present a historical review of polarimetric observations of planetary atmospheres, comets, atmosphereless solar system bodies, and terrestrial materials. We highlight the study of physical and optical parameters of planetary atmospheres. Polarimetric observations of the atmospheres of Venus, Mars, Jupiter and Saturn have made it possible to determine the real part of the refractive index and the cumulative size distribution function for the constituent cloud layers. We describe a simple and reliable method of quantifying absorptive cloud layers of the giant planets and predict the vertical stracture of aerosol layers of planetaiy atmospheres based on the analysis of observational spectropolarimetric data of contours of molecular absorption bands at the center of the planetaiy disk. The method is effective only when experimental data exist in a broad interval of phase angles. Using this method we can determine aerosol sizes in the atmospheres of Uranus and Neptune. 

Fig. 3. Comet Swift-Tuttle at 9.8 fim. Minimum contour level and level spacing are 10% of peak flux (17 mJy). The sun direction is toward the southwest. Comet Swift-Tuttle was mapped at 8.8, 9.8, 11.7, and 12.5 m (Deutsdi et al. 1992) to study the temperature, composition, spatial extent, and evolution of the dust cloud surrounding the comet nucleus. Spectral points at 8.8, 9.8, and 12.5 fim are well-flt by a Planck curve (T = 364 K). There is no evidence for a 9.8 fim amorphous silicate peak but a clear excess is seen at 11.7 fim.

For components that require a high level of protection, the materials could be modeled as a scaled down version of comet probes such as Contour, Giotto, and Stardust. The selection of materials would also be based on the location of the component with the spacecraft If impacts could only occur at a direction perpendicular to the velocity vector of the spacecraft, then that component would receive a far lower fluence level compared to one that is exposed to impact from the front, in the direction of the spacecraft velocity vector. Preferential component location and orientation essentially shields the component from the particle flux and therefore reduces the scale of protection required... 

---