A spacecraft's clock time is an essential aspect of space exploration and communication. It refers to the timekeeping mechanism used by spacecraft devices to measure and record the duration of a space mission. Some synonyms for spacecraft clock time include true solar time, sidereal time, universal time, and mission time. True solar time refers to the time measured by the Sun's apparent position in the sky. Sidereal time is the time measured using the stars' apparent position, while universal time is the time standard used in space missions. Mission time refers to the time calculated based on a specific space mission's duration. Overall, these synonyms are vital in ensuring that spacecraft devices accurately measure and record time to achieve mission objectives.