Japetus was approaching so slowly that is scarcely seemed to move, and it was impossible to tell the exact moment when it made the subtle change from an astronomical body to a landscape, only fifty miles below. The faithful verniers gave their last spurts of thrust, then closed down forever. The ship was in its final orbit, completing one revolution an hour - all the speed that was required in this feeble gravitational field.The above image of Iapetus was snapped by Cassini-Huygens in December of 2004. In life imitating art, Cassini-Huygens has become a satellite of Saturn.
Discovery has become a satellite of a satellite. -- pg 183, 2001 A Space Odyssey