Clusters of yellow lights on the Indo-Gangetic Plain reveal numerous cities large and small in this astronaut photograph of northern India and northern Pakistan. Of the hundreds of clusters, the largest are the capital cities of Islamabad, Pakistan, and New Delhi, India. (For scale, these metropolitan areas are approximately 700 kilometers or 435 miles apart.) The lines of major highways connecting the cities also stand out. More subtle, but still visible at night, are the general outlines of the towering and partly cloud-covered Himalayas to the north (image left).
A striking feature is the line of lights, with a distinctly orange hue, snaking across the center of the image. It appears to be more continuous and brighter than most highways in the view. This is the fenced and floodlit border zone between India and Pakistan. The fence is designed to discourage smuggling and arms trafficking. A similar fenced zone separates India’s eastern border from Bangladesh (not visible).
This image was taken with a 16 mm lens, which provides the wide field of view, as the International Space Station (ISS) was tracking towards the southeast across India. The ISS crew took the image as part of a continuous series of frames, each with a one-second exposure time to maximize light collection. Unfortunately, this also causes blurring of some ground features.
The distinct, bright zone above the horizon (visible at image top) is airglow, a phenomenon caused by excitation of atoms and molecules high in the atmosphere (above 80 kilometers, or 50 miles altitude) by ultraviolet radiation from the Sun. Part of the ISS Permanent Multipurpose Module and a solar panel array are visible at image right.
Astronaut photograph ISS028-E-29679 was acquired on August 21, 2011, with a Nikon D3S digital camera using a 16 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 28 crew. The image has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Jacobs/ESCG at NASA-JSC.