Site Selection for Mars Surveyor Landing Sites: Some Key Factors for 2001 and Relation to Long-term Exploration of Mars

The S i te S e l e c t i o n Process: Site selection as a process can be subdivided into several main elements and these can be represented as the corners of a tetrahedron (Figure 1). Successful site selection outcome requires the interactions between these elements or corners, and should also take into account several other external factors or considerations. In principle, elements should be defined in approximately the following order: (1) major scientific and programmatic goals and objectives: What are the major questions that are being asked, goals that should be achieved, and objectives that must be accomplished [e.g., 1-5]. Do programmatic goals (e.g., sample return) differ from mission goals (e.g., precursor to sample return)? It is most helpful if these questions can be placed in the context of site characterization and hypothesis testing (e.g., Was Mars warm and wet in the Noachian? Land at a Noachian-aged site that shows evidence of surface water and characterize it specifically to address this question). Goals and objectives, then, help define important engineering factors such as type of payload, landing regions of interest (highlands, lowlands, smooth, rough, etc.), mobility, mission duration, etc. Goals and objectives then lead to: (2) spacecraft design and engineering landing site constraints: the spacecraft is designed to optimize the areas that will meet the goals and objectives, but this in turn introduces constraints that must be met in the selection of a landing site [7]. Scientific and programmatic goals and objectives also help to define (3), the specific lander scientific payload requirements and capabilities [6]. For example, what observations and experiments are required to address the major questions? How do we characterize the site in reference to the specific questions? Is mobility required and if so, how much? Which experiments are on the spacecraft, which on the rover? The results of these deliberations should lead to a surface exploration strategy, in which the goals and objectives can in principle be achieved through the exploration of a site meeting the basic engineering constraints. Armed with all of this important background information, one can then proceed to (4) the selection of optimum sites to address major scientific and programmatic objectives [8-9]. Following the successful completion of this process and the selection of a site or region, there is a further step of mission optimization, in which a detailed mission profile and surface exploration plan is developed. In practice, the process never works in a linear fashion. Scientific goals are influenced by ongoing discoveries and developments and simple crystallization of thinking. Programmatic goals are influenced by evolving fiscal constraints, perspectives on program duration, and roles of specific missions in the context of the larger program. Engineering constraints are influenced by evolving fiscal constraints, decisions on hardware design that may have little to do with scientific goals (e.g., lander clearance; size of landing ellipse), and evolving understanding (e.g., assessment of engineering constraint space reveals further the degree to which mission duration is severely influenced by available solar enengy and thus latitude). Lander scientific payload is influenced by fiscal constraints, total mass, evolving complexity, technological developments, and a payload selection process that may involve very long-term goals (e.g., human exploration) as well as shorter term scientific and programmatic goals. Site selection activities commonly involve scientists who are actively trying to decipher the complex geology of the crust of Mars and to unravel its geologic history through geological mapping. By the nature of the process, they are thinking in terms of broad morphostratigraphic units which may have multiple possible origins, defined using images with resolutions of many tens to hundreds of meters, and whose surfaces at the scale of the lander and rover are virtually unknown; this approach and effort is crucially important but does not necessarily readily lend itself to integration with the other elements. Although the process does not operate in a linear fashion, it is critically important that all of these elements are kept in mind because each of these factors must be addressed for mission and program optimization, and if they are lost sight of, crucial opportunities will be missed. But these elements must not be looked upon as individual bastions. The key guiding principle, learned from very hard work in the Apollo Program, is synergistic flow leading to mission optimization. The scientists are not in charge, the engineers are not in charge, and so on. All the elements should be equal partners, and those participating in each element should have a common broader goal, which is striving toward mission optimization. In this way, the process will be synergistic and the whole (mission optimization) will always be greater than the simple sum of the parts. This process requires mutual respect and education, but the rewards are so great, as demonstrated in the later Apollo missions, that any lesser approach is indefensible.