The development of COSYSMO has been an ongoing collaboration between industry, government, and academia since 2001. INCOSE provided expertise as well as a forum for collaboration between stakeholders that led to the eventual development of the model. In 2004, we provided eleven lessons learned from experiences collecting systems engineering data from six companies in collaboration with the INCOSE Measurement Working Group and the Practical Software and Systems Measurement (PSM). These lessons were focused on the development of COSYSMO that was motivated by a similar model from the software domain, COCOMO II, but was a first of its kind for systems engineering. Now that the development phase of the model is completed we take a retrospective view of lessons learned during the ongoing validation phase of the model and present new lessons learned that should help cost model developers, academic researchers, and practitioners develop and validate similar approaches. These lessons include the need for more specific counting rules, an approach to account for reuse in systems engineering, and strategies for model adoption in organizations.

This paper provides an update on the systems engineering model (COSYSMO) being developed by the Center for Software Engineering at the University of Southern California in conjunction with its corporate affiliates and the International Council for Systems Engineering (INCOSE). The model will help organizations better estimate and plan their systems engineering activities that include development, integration, and test. In this light, the COSYSMO working group has focused on establishing the scope of the model through the ANSI/EIA 632 Systems Engineering standard. It was recognized early on that systems engineering activities varied extensively across organizations and projects. The key to collecting consistent data across disparate organizations was to clearly define the content in a WBS that was understandable by the systems engineering and cost estimation communities. Mappings have also established between each organization's or project's WBS elements and the COSYSMO standard WBS elements. The standardized WBS has become the framework for discussion of what systems engineering activities are included and excluded for a particular cost estimate. The paper will cover systems engineering and industry standards, the use of these standards in the COSYSMO model development process, and an analysis of the distribution of ANSI/EIA 632 activities covered in COSYSMO. Nomenclature CER = Cost Estimating Relationship

The applicability of COSYSMO, a systems engineering cost model, is explored in the context of space systems through the analysis of two main assumptions. First, the WBS elements of the model are mapped to a prototypical WBS for space systems. Second, the life cycle phases assumed in the model are mapped to the phases outlined in the latest National Security Space acquisition policy. Through the analysis of these assumptions, the applicability of COSYSMO to space systems can be improved. Moreover, techniques for performing partial estimation of systems engineering by systems engineering activity and life cycle phase are provided to further the applicability of COSYSMO to space systems. Nomenclature

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