Three years after the Soviet Union hit the Moon, Ranger 4 crashed into the Moon on April 25, 1962. However, NASA had intended that the 331-kg spacecraft deliver a seismograph that would survive the landing. A computer failure sent it off course, crashing uncontrolled into the far side.
Ranger 5
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This 343-kg spacecraft missed the Moon entirely. A power failure prevented course corrections and it sailed past the Moon at a distance of 720 km.
Ranger 6
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The 365-kg Ranger 6 crashed into the Moon's Sea of Tranquility on February 2, 1964, hitting its target. However, it failed to take photos and transmit them back to Earth during its plunge. High-voltage arcing during the launch apparently destroyed the camera package, which failed to take pictures on the way in as intended.
Ranger 7
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The 366-kg Ranger 7 finally achieved the primary goal of the Ranger program: transmitting photos to Earth on the way into a hard landing on the Moon's surface. The spacecraft sent back 4,308 TV pictures before it impacted in the Sea of Clouds on July 31, 1964, the first U.S. lunar success.
Ranger carried two wide-angle TV cameras and four narrow-angle cameras. Sun and Earth sensors kept the spacecraft pointing the correct direction, so that a high-gain antenna could transmit the voluminous TV picture data to Earth until just before impact.
Ranger 8
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Ranger 8 repeated the triumph of Ranger 7, sending back 7,137 TV photos of the Moon before it impacted in the Sea of Tranquility on February 20, 1965. To cover more ground, the spacecraft approached the surface along a 42-degree slope, sweeping across the Moon rather than plunging straight in. The final picture had a resolution of two meters. The spacecraft's target was very close to where Apollo 11 later made the first human landing.
Ranger 9
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Ranger 9 transmitted 5,814 photos of the Moon before crashing into the crater Alphonsus on March 24, 1965. The final photograph had a resolution of 0.3 meters, the most detailed look at the surface thus far. The impact was less than 5 km away from the aim point.
