Send a sequence the spacecraft can execute

A command tells a spacecraft to perform an action or change a setting. A sequence orders commands so their dependencies and timing produce an intended result. Turning on a camera, waiting for readiness, pointing, exposing and storing data are different actions; a successful individual command does not guarantee that the complete sequence achieves its purpose.

Ground teams review the sequence against the spacecraft configuration and available resources. A rehearsal or simulation can expose conflicts before upload. The version sent to the spacecraft must be identifiable so the team can compare expected behavior with the events actually reported.

Commands may use specified execution times or other mission-defined triggers. The time convention matters, especially when communication takes minutes. An event observed on Earth happened earlier at the spacecraft. A sequence-of-events record connects onboard activity, ground contacts and the corresponding times rather than treating them as simultaneous.

In a fictional case, one-way light time is four minutes and processing time is ignored. A command transmitted at 10:00 cannot arrive before 10:04. An immediate acknowledgement sent then cannot reach Earth before 10:08. This minimum round trip is a physical delay, not evidence that a controller typed slowly.

Follow a command and its reply

A command accepted into memory has not necessarily executed. A reported execution has not necessarily achieved the physical result intended. For example, software might issue a deployment command while a mechanism fails to move. The team needs appropriate state or sensor evidence to establish the outcome.

Build a fictional checklist with three entries: the correct sequence was received, the intended events occurred at the expected times, and measurements support the desired physical state. These entries prevent a common reasoning shortcut in both operations and software: mistaking successful message delivery for successful completion of the whole task.