3 ms·

I have a crazy idea. The round trip travel time of light to the moon and back is about 3 seconds, and we did leave a mirror up there. At modern modulation rates

I have a crazy idea. The round trip travel time of light to the moon and back is about 3 seconds, and we did leave a mirror up there. At modern modulation rates and with multiple frequencies of light in use at the same time (aka different color lasers), a lot of data can fit into that 3 second window. A memory made of the vacuum of space. The lightest hard drive ever.

Animats 2y ago
Sure. You can also do radio moonbounce, which radio hams routinely do.[1] About 2.5 secs of lag. It takes a sizable antenna. You could probably use that as a delay line. Noisy, so error correction will be necessary. Laser moonbounce is harder to do than radio.[2] Early systems used so much laser power that they had to be equipped with radars to turn the system off if aircraft were in the area. Later systems with safer lasers could detect single photons with a 40cm telescope and transmit a 2KHz signal. [1] https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear... [2] file:///home/john/Downloads/SLR2000_Eyesafe_and_autonomous_single_photoelectro.pdf
- IIAOPSW 2y ago
  This seems more like the airplanes problem than my problem...
  - ben_w 2y ago
    The judge is unlikely to agree with you.
    - IIAOPSW 2y ago
      But I already have an insanity defense, based on the fact I was using the retroreflectors on the moon for data storage.
- LegionMammal978 2y ago
  Would you have a working link to that second PDF?
  - Animats 2y ago
    Here are some SLR2000 papers that are more easily accessible.[1][2] Doing this with low-power lasers requires rather good receiving optics. There has been a major breakthrough in laser data transmission - the first cat video has been sent by laser to and from a spacecraft. "At the time, Psyche was traveling 19 million miles (31 kilometers) from Earth, about 80 times the distance between Earth and the Moon. Traveling at the speed of light, the video signal took 101 seconds to reach Earth, sent at the system’s maximum bit rate of 267 megabits per second."[3] [1] https://ilrs.gsfc.nasa.gov/lw15/docs/papers/SLR2000,%20The%20Path%20toward%20Completion.pdf https://ilrs.gsfc.nasa.gov/lw15/docs/papers/SLR2000,%20The%2... [2] https://ilrs.gsfc.nasa.gov/lw13/docs/presentations/adv_degnan_1p.pdf https://ilrs.gsfc.nasa.gov/lw13/docs/presentations/adv_degna... [3] https://arstechnica.com/space/2023/12/a-cat-video-highlighted-a-big-year-for-lasers-in-space/ https://arstechnica.com/space/2023/12/a-cat-video-highlighte...
  - actionfromafar 2y ago
    Radio link?
pixl97 2y ago
Being the moon is not geostationary this doesn't seem very useful. Also between atmospheric distortion and dust/micro meteorites you'll going to need to be very careful on your error encoding choices.
wheybags 2y ago
No spoilers, but I think you would enjoy this short story: https://qntm.org/transi https://qntm.org/transi

Animats 2y ago

Sure. You can also do radio moonbounce, which radio hams routinely do.[1] About 2.5 secs of lag. It takes a sizable antenna. You could probably use that as a delay line. Noisy, so error correction will be necessary. Laser moonbounce is harder to do than radio.[2] Early systems used so much laser power that they had to be equipped with radars to turn the system off if aircraft were in the area. Later systems with safer lasers could detect single photons with a 40cm telescope and transmit a 2KHz signal. [1] https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Earth_communication https://en.wikipedia.org/wiki/Earth%E2%80%93Moon%E2%80%93Ear... [2] file:///home/john/Downloads/SLR2000_Eyesafe_and_autonomous_single_photoelectro.pdf

IIAOPSW 2y ago
This seems more like the airplanes problem than my problem...
- ben_w 2y ago
  The judge is unlikely to agree with you.
  - IIAOPSW 2y ago
    But I already have an insanity defense, based on the fact I was using the retroreflectors on the moon for data storage.
LegionMammal978 2y ago
Would you have a working link to that second PDF?
- Animats 2y ago
  Here are some SLR2000 papers that are more easily accessible.[1][2] Doing this with low-power lasers requires rather good receiving optics. There has been a major breakthrough in laser data transmission - the first cat video has been sent by laser to and from a spacecraft. "At the time, Psyche was traveling 19 million miles (31 kilometers) from Earth, about 80 times the distance between Earth and the Moon. Traveling at the speed of light, the video signal took 101 seconds to reach Earth, sent at the system’s maximum bit rate of 267 megabits per second."[3] [1] https://ilrs.gsfc.nasa.gov/lw15/docs/papers/SLR2000,%20The%20Path%20toward%20Completion.pdf https://ilrs.gsfc.nasa.gov/lw15/docs/papers/SLR2000,%20The%2... [2] https://ilrs.gsfc.nasa.gov/lw13/docs/presentations/adv_degnan_1p.pdf https://ilrs.gsfc.nasa.gov/lw13/docs/presentations/adv_degna... [3] https://arstechnica.com/space/2023/12/a-cat-video-highlighted-a-big-year-for-lasers-in-space/ https://arstechnica.com/space/2023/12/a-cat-video-highlighte...
- actionfromafar 2y ago
  Radio link?

pixl97 2y ago

Being the moon is not geostationary this doesn't seem very useful. Also between atmospheric distortion and dust/micro meteorites you'll going to need to be very careful on your error encoding choices.

wheybags 2y ago

No spoilers, but I think you would enjoy this short story: https://qntm.org/transi https://qntm.org/transi