What is the ‘artificial moon’ planned in China? By Harikrishnan Nair

Last week, Chinese media reported plans by a private institute to launch an “artificial moon” over the city of Chengdu, in Sichuan province, by 2020. The objective is to provide an alternative means of street lighting and save on electricity. Since then, the idea has not only received wide coverage but also been viewed with some skepticism.

What is known so far
Information about the project has so far been incomplete. People’s Daily Online, the first to report it, said the artificial moon would be a mirror orbiting Chengdu at a height of 500 km. It would reflect the sun’s light at night, and supplement street lighting in Chengdu, which has a population of 1.6 million.

People’s Daily Online reported that the artificial moon’s brightness will be around eight times that of the moon, while China Daily reported that the brightness would be a fifth of a streetlight’s. The People’s Daily Online report said the moon would illuminate an area of diameter between 10-80 km. If the illuminated area is 50 sq km, an AFP report said, it would save an estimated 1.2 billion yuan ($170 million) a year in electricity costs for Chengdu.

If the experiment proves successful, two more such moons could be sent up by 2022, according to the China Daily report, which quoted Wu Chunfeng, chairman of Chengdu Aerospace Science and Technology Microelectronics System Research Institute Co Ltd, and head of Tian Fu New Area Science Society that is handling the project.

What Chinese media did not clarify is whether the project has the official backing of the government. Various other publications reported that they could not confirm the project independently with Wu.

The challenges
At an altitude as low as 500 km, and considering a diameter small enough to be economically viable, accuracy is key. Missing the angle of reflection by even a few degrees would miss Chengdu by miles, a scientist has reportedly said. “If you want to light up an area with an error of say 10 km, even if you miss by one 100th of a degree you’ll have the light pointing at another place,” BBC quoted Dr Matteo Ceriotti, a lecturer in Space Systems Engineering at the University of Glasgow, as saying.
Again, there must be sufficient glow, but if this glow covers a large area, it could potentially affect the daily cycle of animals and plants, and even affect the human circadian system — the body clock. “Many people are in a circadian fog where our physiology is confused,” Richard Stevens, a cancer epidemiologist at the University of Connecticut School of Medicine, told The New York Times.

Is it possible?
The idea to have a satellite reflect light at night isn’t new. In 1993, Russia sent up Znamya 2, a plastic mirror with a diameter of 65 ft. It managed to reflect a narrow beam of light, and astronauts on the then space station Mir reportedly filmed a patch of light on the surface.
“The two-and-and-half-mile-wide beam traveled for about eight minutes across part of the Atlantic Ocean and then across Europe, including Russia,” The NYT reported in 1993. For people on the ground, the light was seen as pulses from a star-like object.
Six years later, Russia launched Znamya 2.5, which was meant to be a larger mirror, but it did not deploy properly. The idea of sending up a giant mirror in the sky died with it. Until now.

Written by Harikrishnan Nair of the Indian Express


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