The favourite pastime of many astronauts on the International Space Station is gazing at the beauty of their home planet. They often remark that it is difficult to pinpoint cities or other manmade features during daytime as they circle Earth at 28 800 km/h.
Wait until night, however, and the lights in our cities stand out sharply from the blackness of the sea and countryside.
The lights we turn on in our houses at night and the lights we use to illuminate public areas also shine upwards, revealing where humans have settled on our planet. NASA astronaut Don Pettit said that each city shows a characteristic ‘signature’ at night, with motorways and airports clearly marked out.
Here, the capital city of Portugal, Lisbon, is shown with south at the top of the image. The brightest area is the city centre. The two bridges connecting the capital to the south – Ponte Vasco da Gama and Ponte 25 de Abril – show up as two straight lines crossing the black Rio Tejo. The peninsular city of Peniche shows up as a blob of light protruding into the Atlantic Ocean at the bottom of the picture.
This image was taken in 2012 using ESA’s Nightpod camera aid that compensates for the motion of the Station. The target stays firmly centred in frame so the final image is in focus. Astronauts can set up the device to take ultra-sharp images automatically using off-the-shelf cameras from 400 km up.
Follow @esaoperations and ESA’s Flickr account for weekly new pictures of Earth’s bright lights and big cities.