This strip of magnetic tape includes a portion of raw telemetry data for the Explorer 7 satellite. This listing is for a section of tape in an acrylic case that was taken from a larger spool recorded in October 1959. In 1955, even before any artificial satellites had been launched, planning for a satellite-tracking network was already underway at NASA. Two years later, the Minitrack network of 11 stations positioned around the globe was completed just 3 days before the launch of Sputnik 1. As satellites populated the skies, interferometers recorded their positions and velocities at each of these stations. This section of tape is from the Minitrack station in Johannesburg, South Africa.