The spacecraft was of the Ranger Block I design and consisted of a hexagonal base 1. 5-meter (4 ft 11 in) across upon which was mounted a cone-shaped 4-meter-high tower of aluminum struts and braces. Two solar panel wings measuring 5. 2 metres (17 ft) from tip to tip extended from the base. A high-gain directional dish antenna was attached to the bottom of the base. Spacecraft experiments and other equipment were mounted on the base and tower. Instruments aboard the spacecraft included a Lyman-alpha telescope, a rubidium-vapor magnetometer, electrostatic analyzers, medium-energy range particle detectors, two triple coincidence telescopes, a cosmic-ray integrating ionization chamber, cosmic dust detectors, and solar X-ray scintillation counters. There was no camera or midcourse correction engine on the Block I spacecraft.