Ranger 7 and Ranger 8 had already photographed the smooth lunar maria that were possible Apollo landing sites. That freed Ranger 9, the last of the series, to go somewhere more interesting to geologists: Alphonsus, a highland crater that might have seen recent volcanic activity. After a course correction on March 23, the probe switched on its cameras 20 minutes before impact and sent back 5,814 good photographs. It struck the Moon at 14:08:20 UT. As it fell, its pictures were broadcast straight to American television.
The Ranger programme had a rough start. Its early probes failed one after another, and the project became a byword for trouble at NASA. By 1965 it had turned things around, and Ranger 9 was its victory lap. Launched on March 21, it was aimed at a point just northeast of the central peak of Alphonsus, a far more complicated landscape than the flat plains its two predecessors had photographed.
Twenty minutes before impact the cameras began to warm up. The first image was taken 2,363 kilometres above the surface. In the final 19 minutes the spacecraft sent back 5,814 photographs, each showing the ground in finer detail as the probe fell. The last one was taken about a quarter of a second before impact, from roughly 600 metres up. The sharpest showed objects around 25 to 30 centimetres across.
The mission is best remembered for how people saw it. Pictures from the B-camera went out directly on national television as the probe fell, so viewers across the United States watched the Moon's surface rush toward them in real time, four years before anyone walked on it.