Below the Detection Floor: Voyager-Class Probes and the Limits of Interstellar Artifact Detection

Abstract The Voyager spacecraft provide a real benchmark for small, low-power, interstellar-bound technological artifacts [NASA Voyager Mission Overview; NASA Voyager Fast Facts]. They remain observable to humanity because they are known objects with known trajectories, known transmission properties, and dedicated Deep Space Network support [NASA Voyager Instruments; JPL DESCANSO Voyager Telecommunications]. That condition is distinct from blind discovery of an unknown object or transmitter. This paper uses Voyager-class spacecraft as a positive control for evaluating the limits of interstellar artifact detection. The analysis distinguishes targeted tracking from blind discovery, communicative intent from practical detectability, and measurement from interpretation. First-order optical estimates indicate that meter-scale to few-meter-scale inert objects remain weakly constrained by current surveys except at close approach or under favorable illumination. Radio detectability is likewise constrained by transmitter power, beam geometry, receiver sensitivity, frequency search space, Doppler drift, and prior knowledge. The paper makes no claims regarding the existence, presence, or likelihood of extraterrestrial artifacts. It argues non-detection becomes evidence only after the detectable object class has been defined.