Definition

Noun The time measured by a specific clock system onboard a spacecraft, which is synchronized with but distinct from timekeeping systems on Earth. It is the official operational time reference for a mission.

Usage

This term is used to specify the precise mission time according to the spacecraft's own timing mechanism. It is a critical technical term in aerospace engineering, mission control, and space science.

Examples

• Noun:
  • The command was scheduled for execution at spacecraft clock time 103457.2.
  • Mission controllers converted the Earth-received time to spacecraft clock time to analyze the instrument's data.
  • A discrepancy was found between the ground computer's time and the spacecraft clock time.

Advanced Usage

• "Spacecraft clock time" vs. "Mission Elapsed Time (MET)": While closely related, they are not always identical. Spacecraft clock time is the raw output of the onboard clock, while MET is often a derived count (e.g., days, hours, minutes, seconds) since a specific mission event like launch. The spacecraft clock time is the primary source for calculating MET.
• "Spacecraft clock time correlation": The process of aligning the spacecraft's clock time with Universal Time Coordinated (UTC) or another Earth-based time standard.

Variants and Related Words

• Onboard Time: A less formal synonym for spacecraft clock time.
• Mission Time: A broader term that can encompass spacecraft clock time, MET, and other time references used in planning.
• Spacecraft Event Time (SCET): The time an event occurs according to the spacecraft clock, as opposed to the time the signal about the event is received on Earth (Earth Receive Time).

Synonyms

• Spacecraft Time
• Onboard Clock Time

Related Phrases

• To set/initialize the spacecraft clock time: The process of starting the clock at the beginning of a mission.
• To read/telemeter spacecraft clock time: To receive the current clock value via a radio signal from the spacecraft.
• A drift in the spacecraft clock time: A gradual deviation of the onboard clock from the reference time standard due to factors like temperature or clock oscillator characteristics.

Noun

1. the clock time given by a clock carried on board a spacecraft