nearby solar collectors, from which the power is then transmitted to receiver stations on earth. Space reflectors for night illumination Another advanced space concept proposal is the notion of space reflectors which reflect sunlight on to small spots on the night side of the Earth to provide night time illumination. An early proponent of this concept was Dr. Krafft Arnold Ehricke, who wrote about systems called "Lunetta", "Soletta", "Biosoletta" and "Powersoletta". A preliminary series of experiments called Znamya ("Banner") was performed by Russia, using solar sail prototypes that had been repurposed as mirrors. Znamya-1 was a ground test. Znamya-2 was launched aboard the Progress M-15 resupply mission to the Mir space station on 27 October 1992. After undocked from Mir, the Progress deployed the reflector. This mission was successful in that the mirror deployed, although it did not illuminate the Earth. The next flight Znamya-2.5 failed. Znamya-3 never flew. In 2018, Chengdu, China, announced plans to place three solar reflectors in orbit around the Earth in hopes of reducing the amount of electricity required to power streetlights. Skepticism has been voiced regarding the technological feasibility of the plan. See also Heliostat Parabolic trough Solar thermal collector Photovoltaics Passive solar Solar tracker Sun gun References Mirrors Solar thermal energy Solar-powered devices Photovoltaics