When to Search for Transmissions from Earth-level Civilizations

The search for extraterrestrial intelligence (SETI) involves searching for electromagnetic transmissions from extraterrestrial sources. Given the vast number of stars to observe and the limited availability of telescope time, each star is typically monitored for about 15 minutes. This approach is primarily tuned to detect signals from advanced civilizations capable of emitting strong high-duty-cycle signals, such as radio beacons. These emitters require high levels of technological development, far beyond our current technological capabilities. In this study, we introduce a novel strategy for scheduling future SETI observations to enhance the chances of detecting an Earth-level technological civilization. By analyzing NASA Deep Space Network's outbound radio emissions over the last two decades, we found that these emissions were predominantly directed towards spacecraft near the Sun-Earth Lagrange points L1 and L2. Our findings suggest that aligning SETI observations with exoplanet conjunctions could improve the probability of intercepting transmissions from civilizations with technological capabilities similar to ours.