Halfway between Los Angeles and Las Vegas, the California country climbs southward out of the sunken basin of Death Valley onto the 3500-foot-high floor of the Mojave desert. On this immense plateau in an area near Goldstone Dry Lake, about 45 miles north of the town of Barstow, a group of 85-foot antennas forms the nucleus of the United States’ world-wide, deep-space tracking network. Here, on the morning of December 14, 1962, several men were gathered in the control building beneath one of the antennas, listening intently to the static coming from a loudspeaker. They were surrounded by the exotic equipment of the space age. Through the window loomed the gleaming metal framework of an antenna. Suddenly a voice boomed from the loudspeaker: “The numbers are changing. We’re getting data!” The men broke into a cheer, followed by an expectant silence. Again the voice came from the speaker: “The spacecraft’s crossing the terminator ... it’s still scanning.” At that moment, some 36 million miles from the Earth, the National Aeronautics and Space Administration’s Mariner[1] spacecraft was passing within 21,600 miles of the planet Venus and was radioing back information to the Goldstone Station—the first scientific data ever received by man from the near-vicinity of another planet. At the same time, in Washington, D.C., a press conference was in progress. Mr. James E. Webb, Administrator of the National Aeronautics and Space Administration, and Dr. William H. Pickering, Director of the Jet Propulsion Laboratory, stood before a bank of microphones. In a few moments, Dr. Pickering said, the audience would hear the sound of Mariner II as it transmitted its findings back to the Earth. Then, a musical warble, the voice of Mariner II, resounded in the hall and in millions of radios and television sets around the nation. Alluding to the Greek belief that harmonious sounds accompanied the movement of the planets, Dr. Pickering remarked that this, in truth, was the music of the spheres. Mariner II had been launched from Cape Canaveral, Florida, on August 27, 1962. Its arrival at Venus was the culmination of a 109-day journey through the strange environment of interplanetary space. The project had gone from the drawing board to the launching pad in less than 11 months. Mariner had taxed the resources and the manpower of the Jet Propulsion Laboratory, California Institute of Technology; the Atlantic Missile Range centering at Cape Canaveral; theoretical and experimental laboratories at several universities and NASA centers; numerous elements of the aerospace industry; and, of course, NASA management itself. To the considerable body of engineers scattered around the world from Pasadena to Goldstone to South Africa to Australia, the warble of Mariner was something more than “the music of the spheres.” Intercept with Venus was the climax of 109 days of hope and anxiety.