Do we have the technology to illuminate a small region on the dark side of the Earth with an artificial satellite in orbit around the Earth? By illuminate I mean bright enough to light objects for regular humans nearby to see better than they could have otherwise. Assume low Earth orbit and no moon to make it easier.

  • $\begingroup$ What form of illumination do you envisage: reflecting the Sun's light, like the Moon does, or generating its own light, acting like an orbiting large light bulb? $\endgroup$
    – Fred
    Nov 15, 2015 at 2:13
  • $\begingroup$ Either way, but generating the light would be so cool. $\endgroup$ Nov 15, 2015 at 2:30

1 Answer 1


Sure. Even a cubesat could do this (if only for a few seconds).

Put a relatively powerful laser (maybe 100W?) on a satellite, focus and aim it at a square meter or so of ground, and light it up. 100 km (LEO) is short enough that a good laser can focus down to a pretty small land area, meaning a smallish laser can focus all of its power on a small area.

A 100W laser is about as bright as 10 100W incandescent light bulbs, and only weights a few kilograms. Add some solar panels and batteries, and your satellite can light up your 1 square meter of dirt for a bit each orbit.

  • $\begingroup$ Awesome! I can picture this being used in rock concerts in the future. $\endgroup$ Nov 15, 2015 at 2:43
  • $\begingroup$ @enigmatic: I can't. LEO is not geosyncronous. Your rock concert would have to be very very short or would need a very large number of satellites. There's also the problems of aiming at something moving past at 8000 m/s. intervening aircraft, clouds, etc. $\endgroup$ Nov 17, 2015 at 16:24
  • $\begingroup$ Why would you prefer monochromatic laser light? "Illuminate a small region" probably means imitating sun light. As a compromise use 3 lasers. You have to show that you can focus such a light source. $\endgroup$ Mar 15, 2021 at 19:21

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