In which mode does the AN/MPQ-64A3 antenna array stop and dither before resuming rotation?

The correct answer is Stare mode. In Stare mode, the AN/MPQ-64A3 antenna array is designed to temporarily stop and then dither or oscillate slightly, allowing it to focus on a specific area for more detailed observation or data collection. This mode is essential for targeting specific threats or gathering additional sensor information about the environment.

The dither feature helps to improve the system's ability to detect and track targets in that localized area by providing refined data. In contrast, other modes like Active mode typically involve continuous rotation, while Standby mode would not engage in active sensing, and Calibration mode focuses on verifying and adjusting system parameters rather than tracking or observing targets. Therefore, Stare mode plays a vital role in enhancing the air defense system's capabilities by concentrating on specific areas.