The radio observatory of the University of California at Berkeley, sited at an altitude of 1043 m at Cassel, California. The observatory was founded in 1960 and since 2012 has been operated by SRI International. It is the site of the Allen Telescope Array (ATA), consisting of 42 antennae of 6.1-m diameter built for the Search for Extraterrestrial Intelligence (SETI) but now also used for more general radio astronomy.

https://www.sri.com/research-development/specialized-facilities/hat-creek-radio-observatory Official observatory website at SRI International.