SOLRAD (SOLar RADiation) 4B was a solar X-ray, ultraviolet, and electronic surveillance satellite. Developed by the United States Navy's United States Naval Research Laboratory, it was the fifth in both the SOLRAD and the GRAB (Galactic Radiation And Background) programs.
Low Earth OrbitRanger 4 was a spacecraft designed to softly impact the lunar surface. Its solar panels were never extended and its sun and earth acquisition system was not initiated due to a failure of a timer in its central computer. It impacted the far side of the Moon on April 26 after 64 hours of flight.
Lunar Impactor