The mysterious robotic protectors exist on all planets you visit, and their purpose is to protect that planet from explorers such as yourself. Depending on the planet, sentinels will range from completely passive to abhorrently aggressive. They are the metaphorical cops, standing by you don't deplete a planet of its resources. They can be aggravated by mining resources irresponsibly, hunting animals as leisure, or taking Vortex Cubes (or other precious items) from the environment. To deactivate the sentinels, either eliminate them all before they are able to call for backup, or hide inside of a building or shelter where you're out of sight.