An all-sky survey is a survey that makes no prior assumptions about the most likely directions to search for a particular type of object, whether it be distant galaxies or signals from an extraterrestrial civilization. An all-sky survey attempts to sweep out entire sections of the sky as they appear from a given location. Whereas instruments used in targeted searches must be continuously moved to track selected objects, those conducting all-sky surveys operate in what is called transit mode; that is, they point in a fixed direction while Earth rotates underneath them. The majority of current SETI projects, such as Project Argus, involve all-sky surveys.