for employing mobility is to enhance the return of valuable scientific data, this report is focused on scientific rather than technological issues. COMPLEX therefore restricted its attention to six case studies, representative of the goals, environments, disciplines, and technologies drawn from previous COMPLEX and NASA reports:

  • What is the nature of the circulation in the lower atmosphere on Venus?
  • What tectonic processes are responsible for the structural and topographic features present on Venus?
  • Is there evidence for extinct or extant life on Mars?
  • What is the physical and chemical heterogeneity within small bodies such as asteroid 4 Vesta?
  • What drives the zonal winds in the jovian atmosphere?
  • What is the internal structure of Europa?

These six case studies are discussed in Chapter 2.

Conclusions and Recommendations

The most important conclusion from this study is that mobility is not just important for solar system exploration—it is essential. Many of the most significant and exciting goals spelled out in numerous NASA and National Research Council documents cannot be met without mobile platforms of some type.

A second conclusion is that the diversity of planetary environments that must be explored to address priority scientific questions requires more than one type of mobile platform. Thus, the simultaneous development of some combination of wheeled rovers, aerobots, aircraft, touch-and-go orbiters, and cryobots is not only justified but is also necessary, as long as there is a scientific justification for the development of each mobile platform. Technology development funds are likely to be scarce and so should be allocated only after a vigorous peer review of the proposed mobility device's technical feasibility and the scientific applications for which it will be used. Technology development activities should be undertaken by the best-qualified individuals and teams within NASA, industry, and academia, as determined by peer review.

With some exceptions, the current technical development efforts are appropriate and well focused. However, it is instructive to compare the tenor of recommendations in science-oriented presentations and of science-centered working groups with the thrust of technical development efforts. The science sources emphasize the need for very capable mobile platforms with these characteristics:

  • Synergy of instruments, that is, a suite of mutually complementary instruments rather than either a small number of instruments or many instruments that are independently conceived and developed;
  • Extensive range and long lifetime; and
  • One or more manipulative devices, such as claws, drills, and the like, some of which are likely to be complex and difficult to develop.

These characteristics define a mobile platform that is fairly large and potentially rather complex. In contrast, the main thrusts of technical development, especially of rovers, are directed at reducing their size and increasing their autonomy. These tendencies create a tension between a model-driven approach to mobility and a technology-driven approach. Reconciling these apparently contradictory priorities and minimizing their impact on the scientific productivity of mobility missions will require close cooperation between engineers and scientists.

Most science objectives defined for future solar system missions call for mobile platforms, manipulative devices, and instruments with significant capabilities. Attaining this level of capability will require reducing the total mass of mobile platforms while maintaining acceptable functional capabilities. The size of a mobile platform needs to be considered as part of a systems optimization based on scientific needs and mission constraints. Although very small mobile systems, such as the micro- and nanorovers currently under development, involve a significant reduction of mass, their payload capacity may be too limited for widespread application unless particular attention is paid to the development of appropriate micro- and nano-instrumentation.

Long-range mobility, whether with rovers, aerobots, or other devices, poses significant navigational chal-



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