Farhana Alam looks into the extraordinary plans for an artificial moon in China
Plans to launch an artificial moon to illuminate the city of Chengdu, the capital of China’s Sichuan province, have been proposed by the main contractor for the Chinese Space Programme; a company named Chengdu Aerospace Science and Technology Microelectronics System Research Institute Co. Ltd. According to the company’s chairman, Wu Chunfeng, the illumination satellite would be eight times brighter than the Full Moon and would light up an area covering 10–80 kilometres (a fraction of the size of Chengdu, which covers 12 400 square kilometres). He claims that the technology has been tested for several years and is sufficiently advanced for the artificial moon to be launched as early as 2020, with plans for another three in 2022 if the first is successful.
Despite the appealing image of an artificial orb illuminating the night sky, the claims made by the company suggest that the satellite would not appear like this at all. Instead, it would involve mirrors in orbit approximately 500 kilometres above the Earth (760 times closer than the Moon), reflecting sunlight back to Earth’s surface. The mirrors would be made from a reflective coating upon solar sails, the angles of which could be adjusted to focus the reflected rays to a particular spot on Earth.
The use of space mirrors is not a novel concept. The original idea came from a French artist; inspired by the Hall of Mirrors in Versailles, he suggested a necklace of mirrors to reflect light to illuminate the streets of Paris. However, his plan never transpired. An attempt at installing space mirrors was made by Russian scientists in 1993, who sent a 20-metre reflective satellite into space, named Znamya (meaning “banner”). It illuminated an area of 5 km on Earth’s surface, moving across Europe like a spotlight, but the satellite was destroyed upon re-entry into the atmosphere. Their second attempt, Znamya 2.5, misfired and was damaged during its launch in 1999. More recently, in 2013, the town square of Rjukan, in Norway, was illuminated by three large mirrors that were controlled and angled using a computer.
Although he revealed no details about the proposed satellite, in an interview with China Daily, Wu Chunfeng justified the idea for an artificial moon by indicating the high cost of electricity for powering street lights at night. He did not, however, give any indication of the costs involved in the development, launch and maintenance of the artificial moon. He also claimed that it could be used to illuminate areas hit by blackouts, e.g. following a natural disaster.
The news has been met by scepticism from the wider scientific community. For a satellite to focus reflected light on such a defined area on Earth, it would need to be in geostationary orbit, which would require it to be 37 000 kilometres above Earth; not the mere 500 kilometres stated by the company. However, increasing the distance of the mirrors would require them to be gigantic if they are to reflect enough light for this purpose.
Furthermore, concerns have been raised about the impact that an artificial moon would have on nocturnal organisms, and on animals such as sea turtles, which use moonlight as a guide. As is the case for many populous cities, Chengdu already suffers from light pollution, which affects the sleep quality of its residents, and adding a satellite that is eight times brighter than the Moon would exacerbate this problem. Exactly how bright the illumination satellite will appear is unclear from the scant information provided by the company. Claims that it would provide a “dusk-like” glow, and be one-fifth of the brightness of a streetlight, appear to directly contradict the original claims made by Wu Chunfeng. It remains to be seen whether these plans will come to fruition, or if they are mere lunacy.