Detecting Extraterrestrial Civilizations with an Earth-level Deep Space Network

A major aspect of the search for extraterrestrial intelligence (SETI) involves searching for electromagnetic transmissions from extraterrestrial sources, often using our own transmissions as a guide. Previous studies have suggested that humanity’s most consistently detectable technosignatures were transmissions from our deep-space networks and interplanetary radar. In this study, we analyze NASA Deep Space Network logs to develop an optimal strategy for selecting SETI targets and scheduling observations to enhance the chances of detecting such networks. With Deep Space Network uplink transmission logs over the last 20 years, we find that these emissions were predominantly directed along the ecliptic plane, towards or directly away from the Sun, and towards other planets. In the case of Mars, we find a species that observed the sun for radio emission during a Mars-Earth conjunction in the past 20 years would have had a 70% chance of detecting one of our transmissions, a 306-fold increase over intercepting our Deep Space Network transmission at a random time. These findings suggest that SETI searches could benefit from prioritizing edge-on exoplanet systems and aligning observation windows with exoplanetary conjunctions or planet-planet occultations because they significantly improve the likelihood of intercepting transmissions from any civilizations employing deep-space networks similar to our own.