American astronaut aboard the International Space Station, Tracy Caldwell Dyson, has recorded a six minute video to deaf children, in American Sign Language. This is the first time ASL has been used on board the ISS, and possibly the first time in outer space - despite it being the 4th most commonly used language in the USA. The purpose of the video was to encourage deaf children not to feel like there are certain things that they can't do, and to pursue a career science if that is what they want. Caldwell Dyson herself says "the only thing deaf people can't do is hear".
Caldwell Dyson learned sign language after befriending a deaf athlete on her university track team. She learned the basics of ASL, and later developed her understanding after encountering deaf students whilst teaching Chemistry at graduate school.
You can watch the full video here.