Concept of operations versus operations concept: How do you choose?

Systems engineering as a discipline is relatively new in the ground-based astronomy community and is becoming more common as projects become larger, more complex and more geographically diverse. Space and defense industry projects have been using systems engineering for much longer, however those projects don’t necessarily map well onto groundbased astronomy projects, for various reasons. Fortunately, many of the processes and tools have been documented by INCOSE, NASA, SEBoK and other organizations, however there can be incomplete or conflicting definitions within the process and implementation is not always clear. For ground-based systems engineers, adopting these existing processes can be confusing. One area of particular uncertainty involves how, when and where to document operations concepts in a way that captures astronomers’ needs, translates them into concise and complete requirements without over-constraining the design teams or over-burdening the project with complex requirements and document management procedures. We present the criteria and outcome of the solution(s) chosen from the perspective of two different projects: a new observatory that is planning its operations (Maunakea Spectrocopic Explorer, MSE) and a new instrument at a longestablished observatory (Gemini - GIRMOS). Quite possibly, this will not answer the question in the title and may raise more questions. We welcome that discussion.