Here are two engineers practising “snow cleaning” on a test telescope mirror for the James Webb Space Telescope. I’m not exaggerating when I say this is the coolest way to dust off any surface without scratching it.
The photo above was taken at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Carbon dioxide gas turns into solid below −78.5 °C temperature at Earth atmospheric pressures, and by shooting the soft, snowy material at the surface, engineers clean gently large telescope mirrors, if they are contaminated during integration and testing.
“The snow-like crystals (carbon dioxide snow) knock contaminate particulates and molecules off the mirror,” explained Lee Feinberg, NASA optical telescope element manager. Pretty chill.