Astronauts are exposed to unique environmental conditions in microgravity that can affect their daily work on board the space station. For example, problems with the ocular surface occur frequently, but have not yet been adequately investigated or treated. Symptoms of dry eye include eye irritation, eyestrain, foreign body sensation and blurred vision. The 'Tears in Heaven' team at Saarland University want to test whether and how tear film and blinking can be examined in microgravity and double gravity.