What brevity term indicates that an object has been acquired and is being tracked with an onboard sensor?

The correct term indicating that an object has been acquired and is being tracked with an onboard sensor is "Track." This brevity term is utilized to communicate that the sensor has successfully acquired the target and is now actively monitoring its movements or status.

Understanding the term "Track" is essential in joint fire support operations, where precise communication is crucial. When a sensor operator declares that a target is being tracked, it informs all involved parties that the target's position and movement can be updated in real-time, thereby facilitating effective decision-making and coordination for engagement.

The alternative choices indicate different aspects of target acquisition or engagement but do not convey the specific action of actively monitoring a target with sensor data. For example, "Captured" might suggest a target has been secured or intended for engagement, while "Spot" generally refers to identifying or locating a target rather than tracking its ongoing position. "Contact" typically denotes an initial identification of a target but lacks the implication of continuous monitoring that "Track" provides.