Spacecraft Event Time is the time an event occurs at a spacecraft. Since it takes time for a radio transmission to reach the spacecraft from the earth, the usual operation of a spacecraft is done via an uploaded commanding script containing SCET markers to ensure a certain timeline of events. Real time commanding of spacecrafts is done rather rarely, mostly in case of time constraints during an emergency event like going into safe mode for an earth-pointed CME of the sun. The Spacecraft Event Time of a singular event on the spacecraft can also be defined as equal to the ERT (Earth-received time) minus the OWLT (One-Way Light Time).

Spacecraft Event Time in UTC is also known as Orbiter UTC, and Earth-received time as Ground UTC.

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