If you want to see the universe, you need to start out by having clean optics, so the lenses need to be cleaned to make sure that not a single grain of dust disrupts the laser beam. To keep their clean room clean, the wave hunters wear gowns, overshoes, hoods, face masks and gloves. In GEO 600, the large gravity wave detector, itself, cleanliness is paramount and there is still work to be done! To ensure perfect interaction between the dozens of lenses and optical systems, each position needs to be precisely calculated and the lenses need to be spotlessly clean, of course. (less info)