Ranger 5 launched 1962

Ranger 5, launched October 18, 1962, was supposed to take pictures of the moon before crashing into its surface, but missed its target.  Its guidance system experienced problems shortly after launch, but NASA sent commands and Ranger 5 was back on course.

Soon, the computer system detected high temperatures and then power generation from the solar panels ceased.    The computer did not command the spacecraft to align with Earth and telemetry at tracking stations malfunctioned.  An electrical short had disabled the solar panels, leaving Ranger 5 with a few hours of battery power.  NASA made several attempts to salvage the mission, but were not successful.  

On October 21, Ranger 5 passed within 724 km of the moon and entered a heliocentric orbit.

Ranger 6 launched 1964

Ranger 6, launched January 30, 1964, was one of a series of lunar probes designed to take close-up images of the moon.  Everything operated as planned and Ranger 6 landed within a mile of its intended target, but due to a failure of the camera system, no images were returned.  Since the cameras were the only equipment on the probe, no other experiments were planned.

The failure of Ranger 6 came on the heels of the assassination of John F. Kennedy just two months before.  In April 1963, Congress had cut funding to the Ranger program by almost 50%, citing "no success had been achieve with any of the missions to date".  Ranger 5 was lost in October 1962.

NASA officials had hoped Ranger 6 would succeed since a week later, they planned to announce their projected budget for $5.3 billion for 1965.  Ranger 7 had already been budgeted and six months later, it became the first successful lunar probe, sending back high definition pictures of the moon.