Functional Requirements for NGAO Christopher Neyman W. M. Keck Observatory NGAO Team Meeting #9 August 24, 2007

2 Requirements life cycle is integrated with design Requirements Elicitation: The art of understanding the needs of the Keck astronomical community Collecting them in a repository for future analysis Examples: science cases, observing scenarios Requirements Selection: The art of deciding which features are appropriate to include in NGAO Realistically we can’t do everything Must balance cost, schedule, risks, and science capabilities Examples: trade studies, error budgets, costs estimation, and risk analysis Requirements Specification: The art of detailing the exact behavior that addresses the features chosen above Examples: the ScRD, SRD, FRD, and Keck baseline instrument requirements Revisit requirements in preliminary and detailed design phases

3 Ideally each requirement will be: Correct: It describes something the scientists want Consistent: It does not conflict with other requirements Unambiguous: It has only one possible interpretation Verifiable: There must exist some means to check that the final system meets the requirement

4 The FRD provides the criteria to evaluate the NGAO subsystems The SRD provides the criteria to evaluate the NGAO system FRD flows down the requirements from design-independent SRD FRD systems chosen to divide NGAO into functions that would be required independent of the selected architecture FRD requirements are architecture specific Two versions of the FRD are scheduled during the system design phase of NGAO The first for system architecture activity (3.1.3) The second as a result of the subsystem design process (3.2)

5 Draft AO and laser system FRD Subsystem breakdown for AO and Laser Needs detailed flow down and checks Mainly TBD and estimated numbers Meet with subsystem leads for review and comments Useful guide to upcoming system design tasks