How is station passage indicated for a TACAN?

The indication of station passage for a TACAN is marked by the moment when the distance measured by the Distance Measuring Equipment (DME) ceases to decrease. As the aircraft approaches the TACAN station, the DME displays the distance to the station, and as the plane flies directly over the station, this distance reaches a minimum and then starts to increase again. Therefore, when the DME distance stops decreasing, it signals that the aircraft has passed directly over the TACAN station, confirming station passage.

The other options do not accurately signify station passage. A change in the bearing pointer can indicate the aircraft's change in direction relative to the station but does not specifically denote passing the station. Changing the TACAN frequency is related to navigating to different stations and does not relate to station passage. Similarly, the glide slope indicator becoming active pertains to vertical guidance for approaches, which is not relevant to determining station passage for TACAN.