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How do targeted SETI searches differ from broad sky surveys?

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artist's conception of Kepler-186f — extraterrestrial intelligence An artist's conception depicts Kepler-186f, the first Earth-sized extrasolar planet found in its star's habitable zone.

In the search for extraterrestrial intelligence, researchers employ two primary strategies: targeted searches and broad sky surveys. These methods differ significantly in their approach to telescope usage, sensitivity, and scope.12

Targeted Searches

Targeted searches, such as Project Phoenix, focus on specific, high-priority targets, typically nearby stars similar in size and brightness to the Sun. Because these programs require exclusive access to radio telescopes, they are generally more sensitive than survey-type projects, allowing for a deeper examination of individual star systems.12

Broad Sky Surveys

In contrast, sky surveys like Project SERENDIP scan large portions of the sky without making assumptions about the specific direction of a potential signal. These surveys are often less sensitive than targeted searches but are highly efficient because they can "piggyback" onto telescopes already performing conventional astronomical observations, thereby securing significant amounts of observation time.1

Both approaches are essential to the SETI effort, as they balance the need for high-sensitivity data from likely candidates with the need to monitor the broader cosmos for unexpected transmissions.12