What is the initial condition of the antenna on the AN/MPQ-64A3 before "OK" is selected during initialization?

The correct answer is that the initial condition of the antenna on the AN/MPQ-64A3 before "OK" is selected during initialization is that it is not rotating.

During the startup process, the system performs a series of self-checks and initialization procedures to ensure that all components are functioning correctly. At this stage, the antenna remains stationary to allow for these checks to complete without the complications that might arise from it moving or rotating. This is crucial as it helps avoid errors during the initialization phase and ensures that the system can accurately assess its operational status before it begins tracking or scanning.

Additionally, remaining stationary allows operators to configure and set the system parameters before the antenna begins to operate fully. Thus, the "not rotating" condition signifies the system is preparing for action and is critical to ensure correct operation once the "OK" is confirmed.