Ranger 2 was a flight test of the Ranger spacecraft system of the NASA Ranger program designed for future lunar and interplanetary missions. Ranger 2 was designed to test various systems for future exploration and to conduct scientific observations of cosmic rays, magnetic fields, radiation, dust particles, and a possible hydrogen gas "tail" trailing the Earth.
Spacecraft design
thumb|left|Artist's conception of Ranger 2 spacecraft.
Ranger 2 was of the Ranger Block 1 design and was almost identical to Ranger 1. The spacecraft consisted of a hexagonal base across, upon which was mounted a cone-shaped tower of aluminum struts and braces. Two solar panel wings measuring 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 scintillation counters.
An inoperative roll gyro caused loss of Agena roll control from the moment of staging. The first burn was performed successfully but the control gas was exhausted trying to keep the vehicle stable so when it came time for restart, the engine shut down after only one second of operation due to ingestion of control gas. Unlike with Ranger 1, the Agena had not operated long enough to achieve any significant ISP and so the probe was left in an even lower orbit. Tracking antennas could not lock onto the probe or send it any commands, nor could the attitude control system stabilize it. Telemetry and instrument data were still received for a few hours, but eventually the orbit decayed too low and after only one day and 19 orbits, Ranger 2 reentered the atmosphere and burned up. As a result of the failure, Agena vehicles would get a version of the Atlas's Spin Motor Rotation Detection System to ensure proper gyroscope operation at launch.