This spacecraft, also known as Explorer 16, was the second in the series of micrometeoroid satellites orbited by NASA. Its purpose was to obtain data on the near-earth meteoroid environment, thus providing an accurate estimate of the probability of penetration in spacecraft structures by meteoroids and allowing a more confident definition of the relationship between penetration flux and material thickness to be derived. The cylindrically shaped spacecraft, about 61 cm in diameter and 192-cm long, was built around the burned-out fourth stage of the Scout launch vehicle that remained as part of the orbiting satellite. Explorer 16 carried stainless steel pressurized-cell penetration detectors, impact detectors, capacitor detectors, and cadmium sulfide cell detectors to obtain data on the size, number, distribution, and momentum of dust particles in the near-earth environment. The spacecraft operated satisfactorily during its 7-month life (December 16, 1962, to July 1963), and all mission objectives were accomplished.