A cat video highlighted a big year for lasers in space
>NASA has invested more than $700 million in testing laser communications in space.
>formatting link
Good call. Laser modulated transmissions can't be intercepted by a third party without being detected.
You’re confusing free-space laser with fiber optics. In fiber you collect all the light, so you can tell if some gets tapped off. You can also see exactly where it happens by using OTDR.
In long range free space, most of the light misses the detector anyway, and there isn’t any way to see where it went.
Cheers
Phil Hobbs
Fair point. Even lasers suffer from beam divergence. I stand corrected, Phil!
Perhaps NASA should just give the project and the money to SpaceX, which already has a working space laser mesh communications system.
"SpaceX Reveals Operation of Over 8,000 'Space Lasers' Across Starlink Satellite Constellation - Enabling Faster Internet" (Sep 26, 2023)
Cute cat.
Eavesdropping on optical communications in orbit is doomed by the photon statistics. An ideal receiver gets a SNR of N/2B, where N is the photon detection rate and B is the bandwidth.
(I expect that the Flying Dutchman has been hanging around SED too much, and so has forgotten what SNR is. ) ;)
Cheers
Phil Hobbs
I happened to be in NL between Christmas and New year. I should have dropped by to see you. I'm sure we'd get along.
Jeroen Belleman
Over what distance?
About 36,000 km (22,000 miles), ground to the LCRD in geosynchronous orbit. Test bandwidth is 1.244 Gigabits/sec bidirectional. Average power is 0.5 watts. LCDR was launched on Dec 7, 2021.
"Laser Communications Relay Demonstration (LCRD)"
"Laser Communications Relay Demonstration (LCRD) Overview" (2021)
"Update on NASAs Laser Communications Relay Demonstration Project" (2018)
"NASAs Laser Communications Relay: A Year of Experimentation"
More:
I once found the link budget calculations, but now I can't find them. Try your luck:
Have something to add? Share your thoughts — no account required.
Ask the community — no account required