Typo. Yep, u need Phalanx Sensors. If you are close enough to the planet (with Phalanx), you will see the Phalanx option in the galaxy by clicking the mouse on the planet. Then you will see the movement of the fleets to this planet.

The higher the level of Phalanx Sensors, the further you see. Remember that this operation costs 50k deuterium.