  MSE will be a massively multiplexed survey telescope, including a segmented
primary mirror which feeds fibers at the prime focus, including an array of
approximately four thousand fibers, positioned precisely to feed banks of
spectrographs several tens of meters away. We describe the process of mapping
top-level requirements on MSE to technical specifications for subsystems
located at the MSE prime focus. This includes the overall top-level
requirements based on knowledge of similar systems at other telescopes and how
those requirements were converted into specifications so that the subsystems
could begin working on their Conceptual Design Phases. We then discuss the
verification of the engineering specifications and the compiling of lower-level
requirements and specifications into higher level performance budgets (e.g.
Image Quality). We also briefly discuss the interface specifications, their
effect on the performance of the system and the plan to manage them going
forward. We also discuss the opto-mechanical design of the telescope top end
assembly and refer readers to more details for instrumentation located at the
top end.
