An encounter occurs when the projected flight path of a spacecraft intersects the sphere of influence, representing the gravitational field of a celestial body. Encounters are displayed in map view by an encounter node and a colorized trajectory path. It's also commonly used in reference to a close approach to another spacecraft or any object shown in map view and Tracking Station. An encounter with a celestial body is automatically shown on the map view, however, an encounter with another spacecraft or an asteroid is only shown if it is targeted first.
Upon arrival at an encounter node, the game switches the orbital reference of the craft to that of the encountered celestial body; an ideal moment to plan maneuvers to stabilize into an orbit. Orbits can be disturbed when time-warping across sphere of influence changes. To maintain a carefully planned orbit, the time warp should be slowed down to 1× as the ship approaches the sphere of influence change. It is recommended to not have a orbit cross encounters, unless you are planning on landing or interacting with the planet/moon.
Encounters are essential for all travels outside Kerbin. They are also required to get back home.
Encounters can be planned with maneuver nodes.