Can Astronauts See City Lights From The ISS?

From space, an observer can see the various footprints of humanity on Earth, including irrigated cropland, road networks, river reservoirs, and coastal structures. However, cities, one of our most significant impacts on the planet, may blend into the surrounding landscape during the day, appearing as gray smudges. At night, however, city lights provide a stunning display of our presence, distribution, and impact on the environment.

NASA and NOAA collaborated to create the first-ever world map of nighttime Earth using nine months of data collected by the DMSP satellite from a height of 830 kilometers above the Earth. The "Night Lights" map, shared widely on the internet, helped people visualize the global distribution of cities and people.

Astronauts, on the other hand, have the extraordinary opportunity to observe the nighttime Earth from a vantage point of 350-400 kilometers above the surface, taking in entire regions at once. With the help of cameras and experimentation, astronauts can capture highly detailed images of our cities at night and share them with the rest of us.

Documenting City Lights From Space

Photographing cities at night from space is challenging due to the International Space Station's rapid movement of over 7 kilometers per second relative to Earth's surface. Unlike daylight illumination, night images of cities require much longer exposure times, which can result in blurry images as the targeted city moves across the camera's field of view while the shutter is open.

However, astronaut Don Pettit, part of International Space Station Expedition 6, constructed a device called a barn-door tracker in 2002 and 2003. This camera mount is commonly used by astronomers and photographers on the ground to capture images of stars and planets in the night sky. Pettit's barn-door tracker allowed him to compensate for the movement of the Space Station relative to the Earth below, keeping the targeted city in the same position in the camera's field of view during the long exposure.

Since then, other crew members have mastered the techniques of nighttime photography, producing hundreds of images of cities from around the world. The increased detail of city lights available from astronaut photography can help refine urban boundaries defined from satellite data. Transportation corridors and major commercial development, such as ports, shopping centers, and cultural icons, jump out of the landscape, and the sharp boundaries created by city lights can provide insight into the effects of urbanization on Earth's ecosystems.