A minor planet is "lost" when today's observers cannot find it because they can no longer accurately predict its location with targeted observations and await serendipitous survey observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observation arc for the object is too short. Many previously lost asteroids (a type of minor planet) were rediscovered in the 1980s and 1990s, but many minor planets are still lost.