The Ranger series was the first U.S. attempt to obtain close-up images of the Lunar surface. The spacecraft were designed to fly straight down towards the Moon and send images back until the moment of impact, to rough-land a seismometer capsule on the Moon, to collect gamma-ray data in flight, and to study radar reflectivity of the Lunar surface. All this was being done in order to "scout" locations for a planned manned landing on the Moon.

The basic spacecraft was 3.1 m high and consisted of a lunar capsule 65 cm in diameter, a mono-propellant mid-course motor, a 5,080-pound thrust retrorocket, and a gold- and chrome-plated hexagonal base 1.5 m in diameter. A large high-gain dish antenna was attached to the base. Two wing-like solar panels, each 5.2 m across, were attached to the base and deployed early in the flight. Power was generated by 8,680 solar cells.

Each Ranger spacecraft had