The Near-Space Unwanted RF Environment as Observed Using VHF Lunar Reflections

Man-made terrestrial radio leakage as reflected off the Moon has been observed with the 305-m Aercibo antenna. The nature and intensity of this leakage gives one some indication of the unwanted radiofrequency (RF) environment for operations in space in the 150-500 MHz range. The experiment consisted of observing both on the Moon and on a nearby patch of blank sky (as a way to identify local sources of interference) for three nights at a variety of VHF frequencies. As predicted in a previous model, we find that the military radars and television (TV) transmitters are main contributors. With regard to the question of possible contact with extraterrestrial intelligence, the Earth indeed is revealing itself to any interstellar eavesdropper who uses the equivalent of an Arecibo antenna at distances up to 30 light years, or who uses a Cyclops system (1000 100-m dishes) up to fifteen times farther away.