Artificial moon

Reasons for being in news

Recently, 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 a artificial moon?

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.

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

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. If we want to light up an area with an error of say 10 km, even if we miss by one 100th of a degree we’ll have the light pointing at another place.

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.

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.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.