Explorer: S-55

Explorer 13 (S 55a) [NASA]

The purpose of the S-55 series were to test vehicle performance and guidance and to investigate the nature and effects of micrometeoroids on the spacecraft systems. 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. They 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.