The Allen Telescope Array (ATA) is a "Large Number of Small Dishes" (LNSD) array designed to be highly effective for “commensal” (simultaneous) surveys of conventional radio astronomy projects and SETI (search for extraterrestrial intelligence) observations at centimeter wavelengths.
The idea for the ATA emerged in a series of workshops convened by the SETI Institute in 1997 to define the path for future development of technology and search strategies for SETI. The advance of computer and communications technology made it clear that LNSD arrays were more efficient and less expensive than traditional large antennas. The final report of the workshop, “SETI 2020,” recommended the construction of the One Hectare Telescope. (1HT) (A hectare is an area equivalent to a square 100 meters on a side.)The SETI Institute sought private funds for the 1HT and in 2001 Paul Allen (co-founder of Microsoft) agreed to fund the technology development and first phase of construction (42 antennas). In October 2007 the array began commissioning tests and initial observations.The array is now being used for radio astronomy observations of our galaxy and other galaxies, gamma ray bursts and transient radio sources, and SETI.