kOS is a scriptable autopilot Mod for Kerbal Space Program. It allows you write small programs that automate specific tasks.
Documentation : http://ksp-kos.github.io/KOS_DOC/
Addon release thread: http://forum.kerbalspaceprogram.com/threads/68089-0-23-kOS-Scriptable-Autopilot-System-v0-11-2-13
Addon development thread: http://forum.kerbalspaceprogram.com/threads/68096-kOS-Autopilot