Transcript Functional Requirements Overview

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