The Ranger 4 spacecraft, which was designed to collect data on interplanetary space, photograph the moon up close and make a rough landing on the lunar surface, was the first American spacecraft to reach another celestial body. The lander was part of the series of nine Ranger spacecraft launched in the early 1960s to explore the moon.
However, a failure in the spacecraft's onboard computer left Ranger 4's solar panels and navigation system undeployed and the spacecraft unable to carry out its science objectives. Ranger 4 crashed into the far side of the moon on April 26, 1962.
- Imaging system
- Gamma ray spectrometer
- Radar altimeter