High-Resolution Microwave Survey to Project Phoenix

From Project Ozma through the early 1980s, most SETI projects used available radio astronomy equipment with modest frequency resolution and limited, offline signal processing.  NASA set out on a SETI technology design and development program with the Project Cyclops study in 1971 and search strategy workshops in 1975-76.  By the early 80s, it was possible to build dedicated, near real time systems for SETI such as Horowitz’s Suitcase SETI.  NASA’s SETI Program developed proof-of-concept and field prototype systems for a Targeted Search of selected nearby stars over a 2 GHz frequency band and a Sky Survey covering the entire sky over a 9 GHz band.  The resulting High Resolution Microwave Survey began observations on October 12, 1992 and was canceled by the US Congress one year later.  The SETI Institute, whose scientists and engineers formed the core of the Targeted Search team, raised private funds (about $27M over eleven years) to continue that search as Project Phoenix.  Phoenix observed nearly 800 stars within about 80 parsecs of Earth, over the available frequencies in the microwave spectrum from 1.2 to 3.0 GHz, in two polarizations, with a resolution of 0.7 Hz.  The search used near real time signal detection and immediate verification of possible ETI signals.  To discriminate against terrestrial interference, Phoenix used pairs of widely separated antennas as a pseudo-interferometer.  The search looked for continuous or pulsed narrowband signals with frequency drift rates of up to ± 1 Hz/sec.  The project observed for a total of 11,136 hours at a combination of major observatories around the world in multiple observing campaigns. While more than a million signals were detected, all proved to be from our own technology.  Second-generation search systems developed for Phoenix are continuing the search at the Allen Telescope Array.  This will soon be replaced by a software-based system running on commodity servers meaning that SETI searches can improve by virtue of new software that the rest of the world can help create.