European Space Agency (ESA) Astronaut Alexander Gerst "calibrates and operates the Sextant Navigation device that is testing emergency navigation methods such as stability and star sighting in microgravity for future Orion exploration missions." Planet Earth photographed from the ISS [5568x3712][OS]

https://go.nasa.gov/2PttFQx via /r/spaceporn http://bit.ly/2OY2Dnw