In order to aim an antenna at Earth, how do unmanned spacecraft find their own orientation (xyz position in space, what direction it is flying and which direction the antenna is pointing)? Are they using a 'camera' to look at stars? Do they need a telescope lens and long tubes to get good image magnification and angular resolution?
How can they move/steer/rotate themselves? Are they using reaction wheels, which run on un-limited electrical power or using limited-supply gas jet thrusters?