The space shuttle was built with a whole host of redundant and backup systems, tested and re-tested to make sure they would engage in case the main one would break down. Many of the satellites operated on the same principle. Conservative approaches worked to fulfill their missions — many times even happily exceeding them — but their downside was they left no room to experimental, and possibly revolutionary, technologies. Those were taken together to comprise the highly experimental, completely risky, and potentially science-changing Deep Space 1 probe.

On this day, September 21, 2001, the Deep Space 1 probe flew by within 1,400 miles of the comet Borrelly, close enough to take black-and-white images and detect the comet’s composition.

The DS1 was launched with the main goal of testing new technologies, and against all odds held up well, which emboldened scientists to steer it towards the comet. Mission Control was even less certain DS1 would survive the encounter, but fitting for a craft that long ago exceeded all expectations, it left the encounter unscathed. If the future generation of comet-exploring craft will incorporate ion engines or a focused solar array, or an advanced self-guiding artificial intelligence system, they will owe a debt of gratitude to DS1.