Simulation Conceptual Modeling For Space Exploration Mission

Within the last two decades, the emphasis in systems engineering research appears to follow a reverse of the development path. This trendency is especially typical in software engineering. Software systems research had an early focus on the testing phase, and then a transition is seen to code generation, followed by program organization and design methodology, and for the past ten or more years the sights have centered on the requirements analysis phase and conceptual design phase. Explanations of the reverse path of research emphasis are from practical project experience: 1) Making concrete representations of a solution possibly is simpler than abstract representations of a problem. "We are not really having a problem coding a solution—we are having a problem understanding what solution to code." (Cook, D.1999). 2) Determining "what to do" is more important than "how to do". So much experience from practical project reveals that the high cost or fatal mistakes are often incurred by incorrect requirements analyzing and incomplete understanding of the problem. Therefore, all of these facts come to a conclusion, which is that the critical factor of determining whether or not the simulation can support its intended uses is problem-domain analysis and concept design in the early stages of a project development. That is obviously true for software engineering, system engineering, and simulation engineering which is a kind of system engineering and has the codependency relationship with software engineering. In modeling&simulation, that plays a role which progresses problem-domain analysis and concept design in the early stages is Simulation Conceptual Model (SCM).In short, SCM is the first step on the road to abstract this real world for fulfilling the simulation application object, it provides SME, developer and VV&A agent the normal description according to the real world, which supports and guides the following design. Correspondingly, the research about its modeling method and exploring process becomes the hotspot of today's modeling&simulation area. Inducting SCM into the concrete simulation project plays significant roles on describing problems accurately, making requirement clearly, directing design development and examining conveniently. What mentioned above is pursued by all the SCM researchers, and also seemed as the final purpose of this paper. Especially for the problem-domain—simulation about space explore target, in order to realize the SCM application, it is necessary to build a deeply concrete scientific simple modeling method and developing process which focus on special characteristic of space exploration mission. However, the international situation about SCM is that uniform definition and method have not been formed because of the differences from theory and disparity on high-level, to say nothing of the concrete modeling description method and exploring process. Therefore, based on the conclusion of predecessors' opinion and works, we first propose the detailed SCM template of space exploration mission—SESCML, and its developing process—SECDP.First of all, general signification and roles of SCM was summarized, which established theory basis for continuing studying. Characteristics of space exploration mission, such as mission classification, runtime infrastructure, and simulation requirements and so on, were analyzed. Several typical views on content of SCM were summed up. The position of SCM in the process of simulation system development was investigated in details. In the guideline of characteristics of space exploration mission and the developing position of SCM, and based on the summarized contents, the framework of simulation conceptual model aimed at space exploration mission was confirmed.Based on the framework of SESCM, the modeling method of SESCM was researched in further. By analyzing features of structural and object oriented methods, a modeling ideology of simulation conceptual model was founded, for which object oriented method lays foundation, which use structural method as modeling process. In this direction, combining general principle of simulation modeling, the SESCML, modeling language and model template, which aimed at SESCM was brought forward and established. SESCML consists of three levels—system level, model level, and design level, four models—entity model, function model, process model and environment model, and 15 kinds of diagram templates, such as Simulation Objective Lists, Simulation Context, Entity Structure Diagram, Task Flow Diagramand so on. Significations, roles, representions and interrelationships of all kinds of levels, models and diagrams were expounded in this article.In order to support the development of SCM that based on the SESCML template, this paper proposes SECDP-- the developing process model about SESCM. SECDP is built on the foundation of general modeling theory and it exists during the entire lifecycle from knowledge acquiring to knowledge modeling. Also, it concludes the fatal activity systematically and comprehensively, which are consisted of five steps during the exploring process of SESCM. Focusing on the model validation, this paper studies VV&A basic meanings and principle; meanwhile, we propose the primary assessment method and general conceptual validation process.At last, based on the research of Mars exploring, guided by the SECDP, and planed by SESCML template as the criteria, we finished lots of exploring activities such as simulation object analyzing, characteristic analyzing, modeling, and establishing federate relationship and so forth. Thanks to these activities, we finally build the SESCM of Mars exploring target systematically.