Identifying Casual SETI Transmissions and Ultra-Faint RFI with Cumulant Imaging

Abstract: Techniques for identifying radio beacons transmitted by extra-terrestrial civilizations are well advanced. However, the casual broadband emission from standard radio communication is much harder to detect, and counter-intuitively casual Earth radio transmissions are becoming more difficult to identify as we more efficiently utilize the radio spectrum. In this paper we examine the electric-field statistics behind radio communication and re-conceptualize standard radio imaging as the first non-zero cumulant. This leads us to images of the higher cumulants where the natural stochastic emission from astrophysical sources disappears, leaving images of only modulated sources of radio communication. Faint SETI and RFI sources stand out in these cumulant images, enabling identification of faint communication that is undetectable with current techniques.