4 ms·

Lasers are the future. http://www.space.com/23350-laser-space-communications-incredible-technology.html http://www.space.com/23350-laser-space-communications-in

by dharma1 11y ago

Lasers are the future. http://www.space.com/23350-laser-space-communications-incredible-technology.html http://www.space.com/23350-laser-space-communications-incred... Easier for shorter distances (I think Facebook is researching this for satellite networks?) however it becomes more challenging the deeper we go into space because the beam is narrow - but the bandwidth is fantastic.

ginko 11y ago
At the distance from Pluto to Earth, Earth's diameter amounts to about 1.5 * 10^-4 degrees in angle. Precisely pointing a laser beam at a given target, even a large one, at that distance seems almost impossible. Especially since the space probe probably won't stay perfectly still but will always slightly tumble.
- BurningFrog 11y ago
  As long as it can get feedback ("a little to the left") somehow, it seems doable to this software expert.
  - icegreentea 11y ago
    Its a 5 hour time lag from Earth to Pluto - it's going to be one hell of a bad time doing feedback control on that link.
- mikeash 11y ago
  I'm guessing that the laser itself is wider than that. According to this fellow, a realistic beam width is 3.5 microradians: http://space.stackexchange.com/questions/2005/how-much-power-loss-does-the-llcd-suffer-in-transit/2006#2006 http://space.stackexchange.com/questions/2005/how-much-power... That's about 2e-4 degrees, wider than Earth as seen from Pluto.
- jhallenworld 11y ago
  Is the earth visible in an optical telescope from the spacecraft? This should be the basis for automatic tracking... (transmit the laser through the same telescope back to earth). The transmitter on earth could track on the "star" of the laser from the spacecraft. I've been trying to understand the noise temperature of erbium doped fiber amplifiers- not nearly as good as DSN masers.

4 ms·

Lasers are the future. http://www.space.com/23350-laser-space-communications-incredible-technology.html http://www.space.com/23350-laser-space-communications-in

by dharma1 11y ago

ginko 11y ago
At the distance from Pluto to Earth, Earth's diameter amounts to about 1.5 * 10^-4 degrees in angle. Precisely pointing a laser beam at a given target, even a large one, at that distance seems almost impossible. Especially since the space probe probably won't stay perfectly still but will always slightly tumble.
- BurningFrog 11y ago
  As long as it can get feedback ("a little to the left") somehow, it seems doable to this software expert.
  - icegreentea 11y ago
    Its a 5 hour time lag from Earth to Pluto - it's going to be one hell of a bad time doing feedback control on that link.
- mikeash 11y ago
  I'm guessing that the laser itself is wider than that. According to this fellow, a realistic beam width is 3.5 microradians: http://space.stackexchange.com/questions/2005/how-much-power-loss-does-the-llcd-suffer-in-transit/2006#2006 http://space.stackexchange.com/questions/2005/how-much-power... That's about 2e-4 degrees, wider than Earth as seen from Pluto.
- jhallenworld 11y ago
  Is the earth visible in an optical telescope from the spacecraft? This should be the basis for automatic tracking... (transmit the laser through the same telescope back to earth). The transmitter on earth could track on the "star" of the laser from the spacecraft. I've been trying to understand the noise temperature of erbium doped fiber amplifiers- not nearly as good as DSN masers.