Smart solutions for Light pollution

For almost the entire human history when the Sun goes down the western horizon and dusk time gets over blue sky used to turn black to be lit by planets, thousands of stars, Milky Way and dozens of fuzzy nebulae. If the Moon is not there to spoil the show by its light, astronomers have the universe available to to learn its secrets and enjoy its beauty. All this is lost to the growing menace of light pollution, and we are left with hardly a few dozen stars and five planets visible to naked eyes on a moonless night. We have lost access to the universe to the made race of technological progress, night time lighting. Even at darker locations a new kind of light pollution is spreading, this time the problem is coming from up, from the sky, it is the light reflected from the satellites.

Earlier there were less than 2000 satellites but except a couple of hundreds and the ISS and Hubble space telescope must have been invisible to naked eyes. Communication satellites, especially the less than 100 Iridium satellites, were giving off occasional flare, 24 GPS satellites were all invisible so most of the time the sky was visibly dark for observation. SpaceX ended this all with more than 5000 satellites striking across the sky all the time and photobombing astronomical images. In professional astronomy sensor saturation and ghostly after image is a serious issue. As many as 10% of Hubble images are rendered useless due to satellite streaks.

One traditional way to handle this issue was to use ephemeris or ‘schedule’ to avoid this photobombing is not workable now as most ‘swarms’ launched by spaceX uses AI to plan their changing trajectory. On the ground availability of cheap LED lighting is making light pollution worse as most planners and people themselves are unable to distinguish between well lit and brightly lit. There is so much stray light spilling in the sky due to badly designed lighting fixtures or naked outdoor light bulbs. This loss of the night is causing serious health problems for us humans and threatening to loss of biodiversity for the future of life as a whole on the planet.

There are two technological solutions to solve this problem. First one is most important and easier to implement is to use better light fixtures to have better well lit urban and rural spaces. It will reduce not only the number light sources needed but also cut down the cost of lighting too. In fact, governments and agencies other involved in controlling light pollution should promote use of CFL or LED lighting as unlike traditional electric bulbs with filament don’t give a continuous stream of light but pulsed as per the frequency of the AC current. One startup has designed a height speed shutter for a telescope camera, ‘Stealth Transit’ to mitigate this satellite photo bombing. It uses a wide field camera to detect a satellite before it enters the telescope’s field of view and closes the shutter. As soon as the satellite completes its transit from the field of view, the shutter opens again to resume imaging by the telescope.

Second solution is to use a high speed shutter in synchronisation with the pulse lighting of the CFL and LED. Both the sources flicker between 50-60 or 100-120 times per second. Human eyes and brain doesn’t notice this flickering and perceives it as continuous lighting. This has potentially fascinating implications for astronomy. the combination of coordinated “flicker” on a city-wide level with a high-speed shutter for telescopes and observatories.If we can coordinate all the lights within a certain region including residential, commercial, and industrial lighting, as well as street lights and vehicular lights to flicker in-phase with one another, then simply closing the telescope’s shutter when the light flashes go “on” and opening the shutter when the light flashes go “off” could enable astronomy to be conducted even in significantly light polluted areas. That’s the idea behind the Dark Sky Protector, developed by the same group that developed the StealthTransit shutter system.