NASA’s New Horizons probe finally reached Pluto and its dwarf moon, Charon. After traveling 9 years and 3.6 billion miles, New Horizons took hundreds of images on Tuesday morning. With three cameras on board, the most impressive is "Ralph." A camera equipped with a 75mm lens at f/8.7, capable of capturing visible light and some infrared light. As New Horizons traveled away from the sun, temperatures drop causing materials to shrink. Lisa Hardaway, an engineer at Ball Aerospace in Colorado knew "Ralph" would have to be built almost entirely of one type of material.

“We actually built the mirrors and the chassis out of aluminum so that as they shrink, they would shrink together, to maintain the same focal length. We could do a reasonable test on Earth and still expect the same quality image,” Hardaway says.

Even the camera’s mirrors were made out of aluminum. To turn dull aluminum into mirrors, Ball sharpened it with diamonds. The lens was one of the few pieces of the camera that could be safely made out of glass.

A huge mission. An impressive camera. One set of historic photographs.