The Berkeley SETI system, SERENDIP (an acronym: Search for Extraterrestrial Radio Emission from Nearby Developed Intelligent Populations), enables continuous observing on large radio telescopes without requiring dedicated telescope time. In this system, data being collected as part of the ongoing astronomical observing program are processed automatically in a search for narrow band signals which are highly unlikely to be of astronomical origin. Any such signals detected are noted, along with relevant observational data, for further study.
This approach obviates the need for dedicated telescope time and thus allows us to accrue a large volume of data on major telescopes. A commensal SETI program such as this is not free to choose observing frequencies and sky coordinates. However, in view of the plethora of postulated frequency regimes for interstellar communication and the large number of potential sites for civilizations which have been suggested, this is not necessarily a disadvantage.