ion chamber operated normally from launch through 25 August 1959. The GM tube operated normally from launch through 6 October 1959. Micrometeorite A micrometeorite detector (micrometeorite momentum spectrometer), which employed piezoelectric crystal microphones as sensing elements, was used to obtain statistics on the momentum flux and the variations of flux of micrometeorites. Although pulses were detected, the experiment returned no data of scientific value. Proportional Counter Telescope A triple-coincidence omnidirectional proportional counter telescope was used to observe protons (with E>75 MeV) and electrons (with E>13 MeV) in the terrestrial trapped radiation region. The scientific objective of the telescopes was to determine some of the properties of high-energy radiation in interplanetary space, including the proportion of counts due to X-rays versus those due to protons and other high-energy particles. Comparison with results from the Cosmic Ray Ionization Chamber makes it possible to determine the type and energy of particles responsible for the measurement. Each telescope consists of seven proportional counter tubes, six in a concentric ring around the seventh running parallel along their lengths. These bundles of tubes lie on their sides projecting through the top of one of the equipment boxes in the hexagonal base of Ranger 1. Three of the outer tubes are exposed to space and three project into the equipment box. Each set of three is connected electronically into a group that feeds into a pulse amplifier and pulse shaper. The central tube feeds into its own equivalent circuit. The two telescopes were designated a "low-energy" and "high-energy" telescope, differing only in the amount of shielding and its configuration. The counters in the high-energy telescope were 3-inch long, 0.5 inch diameter brass tubes with a thickness of 0.028 inches. A lead shield of 5 grams per cm2 thickness surrounds the entire assembly. The low-energy unit has the same size tubes, but made of steel with a wall thickness of 0.508 ± 0.0025-mm. Half the assembly has 5 grams per cm2 lead shielding along the length of the tubes. The unshielded half of the assembly is the exposed portion that particles can reach without encountering spacecraft structural material, giving an angular resolution of under 180° for low-energy particles. The low-energy telescope can detect protons with energies greater than or equal to 10 MeV and electrons greater than or equal to 0.5 MeV. The high-energy telescope detects 75 MeV and above protons and 13 MeV and above electrons in