NASA has a massive collection of photographs of the Earth. To date the library of photos, taken between the 1960s and 2014 consists of 1.8 million images with more being added daily. The problem is that NASA doesn’t know what, exactly, is represented in all of those images.

Now, all of those photos have been made available through the Gateway to Astronaut Photography of Earth. It is the most complete collection of such photography to date. About 1.3 million of the images were taken from the International Space Station and about 30 percent of those at night.

More recent images were taken using the European Space Agency’s Nightpod. The Nightpod takes much clearer images because it compensates for the space station’s speed, which is approximately 17,500 miles per hour. However, while the pictures may be clearer, taking photographs at that speed means that it’s not always clear which part of the Earth has been photographed.

NASA and the Complutense University of Madrid (UCM), are now looking for help in identifying cities and other landmarks depicted in the photographs. The citizen science project is called Cities at Night and is decided into three parts: Dark Skies of ISS, Night Cities, and Lost at Night.

The first component, Dark Skies, simply asks volunteers to divide images into one of three categories: cities, stars and other objects. No specific expertise is required for this component.

“Anyone can help. In fact, without the help of citizens, it is almost impossible to use these images scientifically. Algorithms cannot distinguish between stars, cities, and other objects, such as the moon. Humans are much more efficient for complex image analysis.” said Alejandro Sanchez, a Ph.D. student at UCM in a statement.

Night Cities, the second component, requires a good knowledge of the geography of a city or region. Volunteers are asked to identify specific points in night images and match them to positions on maps. This data can then be used to generate light maps of cities.

Lost at Night is the most difficult of the three components. Volunteers are asked to look at an image which represents a circular 310 mile region and identify cities.

“We don’t know which direction the astronaut pointed the camera, only where the station was at the time the image was taken. Some images are bright cities but others are small towns. It is like a puzzle with 300,000 pieces,” said Sanchez.
So far volunteers have classified 20,000 images, however to insure accuracy each photograph must be classified by multiple individuals.

The primary goal of the project is to produce an open atlas of night time images which can then be used by the media, the public and scientists.

Among other things, scientists will be able to use the data to determine the energy efficiency of a city based on the types of light sources. The data can also be used to determine the economic health of a city, evaluate road and public safety and measure light pollution.

“A clear example is comparison of Madrid and Berlin. Madrid is the capital of Spain, a country facing a major economic crisis. It is much brighter in astronaut images than Berlin, the capital of Germany, the country with the healthiest economy in Europe. Perhaps that is an indication that Germany more efficiently manages its resources. The images can provide evidence and data to verify that,” said Sanchez.

People interested in participating in the project can find out more at the Gateway to Astronaut Photography of Earth website.