Comment by icegreentea2 | Hacker News Reader

Comment by icegreentea2 | Hacker News Reader

Here's a paper (from July 2025) on previous steps in this program, getting up the initial testing in flight. Maximum uplink laser power of 20W, though they got good performance all the way down to 2W. The sat has a laser pointing down that was used to help lock on, but it's not clear if it has any meaningful downlink capability, all discussions are about uplink capability. Lots a nerdy details here.

https://www.spiedigitallibrary.org/conference-proceedings-of...

In addition, here's a random paper on the testing performed on the space borne laser terminals - https://icsos2012.nict.go.jp/pdf/1569586689.pdf

This tells us that the laser terminals have a FOV of +/-2.5mrad in acquisition mode (so before lock on), and +/-0.5mrad in communication/tracking mode. This corresponds ~100km and ~20km radius FOV from GEO to surface.

Uplink alone can be significant for clandestine operations.

You can have a stealth drone which is effectively invisible to SIGINT transmitting real time intelligence to a satellite whilst either operating autonomously or receiving commands via a wide area encrypted broadcast (yes I know you can theoretically detect receivers through signal attenuation but at these distances it’s effectively impossible to do).

> yes I know you can theoretically detect receivers through signal attenuation but at these distances it’s effectively impossible to do

Well if that's part of your threat model then you should also consider the RF put out by the motors. Remember the part where we densely blanked the inhabited parts of the world with highly sensitive antennas over the past 3 decades?

Yeah, spark of engine is something what can be seen on SIGINT for dozens of kilometers.

So unless jet engine is used (which rarely is on reconnaissance drones) then the drone will be spark lighthouse in the sky.

They say "error-free connection", which implies 2-way communication, right?

You can embed parity and error recovery bits in a one way stream.

This is how one way fiber optic connections for air gapped systems work.

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