Prove the requirement—and check the purpose

Verification — open definition asks whether the realized system meets its specified requirements. Validation — open definition asks whether it serves the intended use and stakeholder need in the relevant context. The same activity may contribute to both, but the questions differ. A system can meet a poorly chosen requirement while still failing the mission’s actual purpose.

In a fictional flood-mapping project, a product arrives within its specified six-hour deadline but local users needed it within two hours. Delivery may satisfy that particular requirement — open definition while the service fails the intended decision timescale. The lesson is to repair the requirement and design connection, not to redefine success afterward.

Verification evidence can come from testing, analysis, inspection or demonstration as appropriate to the requirement. Counting installed connectors is different from measuring communication performance under load. Choose a method that can actually establish the required property and state its limitations.

A successful launch proves an important event occurred. It does not by itself verify every later instrument measurement or validate every promised service. Mission claims should identify the stage and capability established by the available evidence rather than allowing one success to stand for all remaining work.

Suppose testing shows a camera needs longer exposures than planned. That can affect pointing stability, observation duration, power, data cadence and operations. A controlled revision follows those dependencies, updates the relevant requirements and changes the verification plan where necessary.

Record why the revision is needed and which tests must be repeated. If a workaround changes the scientific coverage, the team must reassess whether the original question can still be answered. A design is not complete merely because its individual documents no longer show an obvious error.

Before claiming readiness, connect each essential requirement to applicable evidence and each important operational need to a validated use. Unresolved issues should be explicit, with their implications understood. This is a structured engineering judgment rather than a claim that testing can remove all uncertainty.

The course began with a question and ends with a result that can be evaluated against it. That loop is what makes mission design a learning process: observations change models, tests change designs, and documented decisions keep the complete system coherent.