The answers to these questions lie within the small device itself. The reflector, which consists of an inclined metal frame sitting on a base plate, appears relatively unremarkable at first glance. But inside it holds something unbelievable: 100 triple prisms that have been trained on the Earth for more than 50 years. These prisms are not made of regular glass, but rather high-tech quartz glass. Thanks to these quartz glass prisms, the reflector has been bouncing laser beams reliably back to Earth for almost five decades now. It is the only Apollo space experiment still running.
This amazing longevity is only possible because quartz glass can withstand the extreme temperatures on the moon (swinging from -150°C at night to 135°C in the day) and the aggressive UV radiation. Fifty years after the reflector went to work, its prisms are still unclouded. Quartz glass does not deteriorate with age. It is so pure—99.9999%—that impurities have to be measured in parts per billion (ppb). Because of this extreme degree of purity, the few laser photons that reach the reflector after a nearly unimaginable distance of 384,000 kilometers are sent back to Earth with minimal scattering. The concentrated laser pulse sent by scientists at ground control may be extremely powerful and strong, but it still fans out over two kilometers on the way to the moon. In order to even be able to conduct measurements, the reflection must not be scattered due to impure materials. Impure quartz glass would send the few photons that actually hit the reflector into the depths of outer space rather than reflecting them back to Earth. NASA engineers and Bendix Corp. (now Honeywell Aerospace), which was responsible for the Apollo 11 experiments package, already recognized back in the 1960s that Heraeus quartz glass is extraordinarily homogenous. That’s how Heraeus became part of the Apollo 11 mission and helped write moon landing history.