US astronaut Frank Rubio explains what he missed the most about life on Earth and the record-breaking challenges he faced while on the ISS. Being able to peer out of the window of the International Space Station (ISS) to see the Earth sprawled out beneath you is the ultimate dream of any would-be astronaut. Yet living and working on the ISS brings its own unique challenges that only a handful of our best and brightest will ever get to experience firsthand. There’s so much to do and see in space but as American astronaut Frank Rubio explains, there’s also so much to miss back home. US astronaut…