The Science Channel’s cable show, “NASA’s Unexplained Files” reports on mysterious “music” heard by the crew of Apollo 10 while they were orbiting the Moon—on the far side, out of radio contact with the Earth. In fact, most of the Apollo crews heard strange whoops and whines on the comm loop at one time or another during their missions. Are these strange sounds evidence for aliens hovering just beyond the astronauts’ reach? To understand how the sounds may have originated, you must understand a little about how radio works and how electromagnetic interference is created and mitigated.
The Apollo spacecraft required several different radio links of different frequencies in order to safely conduct the missions to the Moon. These included telemetry sent down for their onboard systems (to allow Mission Control to monitor the health and performance of the vehicle), voice and biomedical information from the crew, and navigational data, including information on ranging to the surface so that the spacecraft could safely approach and land on the Moon.