icegreentea2 4h ago

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.

Meneth 10h ago

"low-latency links", says the article. I wonder if they consider 500 ms ping to be low, or if they want to replace Geostationary with Low Earth Orbit.

adev_ 4h ago

> "low-latency links", says the article. I wonder if they consider 500 ms ping to be low, or if they want to replace Geostationary with Low Earth Orbit.

Directional laser beams are orders of magnitude to jam compared to radio wave. That alone makes it of big interest for military applications, even with 500 ms latency.

There is several known cases where jamming caused the loss of costly military drones.

https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incid...

Laser comms could prevent that entirely.

shagie 4h ago

> Directional laser beams are orders of magnitude to jam compared to radio wave. That alone makes it of big interest for military applications, even with 500 ms latency.

I am reminded of RFC 1217 - Memo from the Consortium for Slow Commotion Research (CSCR) https://www.rfc-editor.org/rfc/rfc1217

    2. Jam-Resistant Land Mobile Communications

       This system uses a highly redundant optical communication technique
       to achieve ultra-low, ultra-robust transmission.  The basic unit is
       the M1A1 tank.  Each tank is labelled with the number 0 or 1 painted
       four feet high on the tank turret in yellow, day-glo luminescent
       paint.  Several detection methods are under consideration:

Spoom 2h ago

I love that this was ostensibly written by Vint Cerf.

shagie 1h ago

It's listed in his computer science bibliography https://dblp.org/pid/c/VintonGCerf.html and https://en.wikipedia.org/wiki/Vint_Cerf#Author

Though the edit for that authorship to the RFC came much later. https://datatracker.ietf.org/doc/rfc1217/history/

SlightlyLeftPad 3h ago

Could these not be jammed by blasting the same wavelength laser at said geostationary satellite?

tiagod 3h ago

Please correct me if I'm wrong, but I guess if you aim well enough, there could be a very long, narrow, non-reflective cylinder in front of the receiver that would block all light that is not coming exactly from the direction of the target satellite.

scottLobster 59m ago

"If you aim well enough" is doing a ton of work there. Precise real-time optical tracking of a satellite from a moving platform is an extremely difficult problem. Even if the satellite itself is geostationary, it would also have to rotate to keep the "cylinder" pointed in the right direction to maintain signal.

I suppose you could make a "cylinder" or "cone" broad enough that, if the threat was static, could blot-out attempted jamming from only certain regions while staying open facing toward friendly zones.

Onavo 3h ago

You will probably need to increase the gain (better lens, photomultipliers) on the receiver photodiode too.

fidotron 9h ago

Getting it to work with one end stationary first sounds like a reasonable development plan. LEO adds a lot of complexity, but with huge benefits.

OTOH the number of engineers that focus on throughput over latency is quite staggering.

amarant 1m ago

Leo seems easier to me. Geostationary is really far away. Leo is much, much closer. It's easier to hit a buck thats running right past you than to hit a stationary target across the Atlantic.

Especially if you yourself are on a moving platform

IrishTechie 9h ago

I guess if your goal is just to stream aircraft telemetry and black box like recordings then latency may not be high on the agenda.

connicpu 8h ago

Black box data doesn't need that crazy throughput either though. Traditional RF is much easier to get right, and works even when the aircraft starts losing track of where it is and stops being able to track the satellite with its laser

SiempreViernes 8h ago

I think it's the opposite? For small telemetry you want it now, but for the big data products there's no hope of "now" and so you settle for soon.

rtkwe 3h ago

Geostationary is easier to hit than a LEO constellation like Starlink. With an LEO target you need to switch at least every 2-4 minutes, Starlink ground stations can switch multiple times per minute but that's for obstacle avoidance in the air you'd only have to switch when the current target moves out of LOS entirely.

pottertheotter 7h ago

I’ll take 500ms ping for those speeds while temporarily on a plane.

oofbey 6h ago

No doubt! I’ve measured literal 5 minute ping times on airplanes. 300,000ms. Where are the buffering the packets!?

raddan 5h ago

My guess is that you're getting retransmissions because of dropped frames, not because there's some huge buffer in the sky.

reactordev 5h ago

Indicated airspeed 280kts, ground speed 470kts, FL410, the packets are trying to catch up…

JackFr 5h ago

I like "huge buffer in the sky".

That's where I imagine all my deleted data goes.

0_____0 1h ago

we're all just riding the ring buffer of samsara, maaan

BobbyTables2 4h ago

There’s one huge buffer in the sky!

The huge buffers are at the two endpoints (:->

utopiah 9h ago

Nice, if you want a bit more details on the TNO side https://www.tno.nl/en/newsroom/2026/02/airbus-tno-demonstrat... relying on https://connectivity.esa.int/archives/projects/ultraair

tart-lemonade 7h ago

> These developments entail a future where travellers could enjoy reliable, high‑speed internet while flying, and where people on ships or in vehicles crossing remote regions can stay connected without interruption.

How reliable/feasible would this be on the ground? From what I understand, shining non-trivial lasers in the sky is a massive liability because of the potential to interfere with aircraft. I don't see anything about the wavelength used, but even if it's outside the visible spectrum, it would still be subject to interference from aircraft when used on the ground or at sea.

joezydeco 6h ago

It's being implemented. I thought I saw that Amazon Leo (nee Kuiper) was going to lean on it pretty heavily.

https://www.techbriefs.com/component/content/article/47300-u...

mynameisvlad 3h ago

That talks about inter-satellite links (which Starlink uses already). Parent comment asked about ground <-> sat

Jtsummers 6h ago

Optical links are being developed for use from fixed ground stations.

https://news.ycombinator.com/item?id=46709548 - Discussion from a month ago with several links for a recent example.

db48x 8h ago

Some miniaturization required.

nashashmi 4h ago

How does Air force one accomplish their data connection?

icegreentea2 4h ago

Air Force One (and all of the other US flying command posts) are basically giant collections of various antennas.

Here's an article from 2017 about (then) recent installation of what were almost certainly satellite communication antenna.

https://www.twz.com/10470/air-force-one-jet-reemerges-with-u...

cm2187 10h ago

But that means you need to have a different laser pointed at every single individual aircraft right? Doesn’t really scale.

amelius 10h ago

I suppose you can do time-sharing. And use mems-mirrors to quickly move the beam between different targets.

esseph 8h ago

Laser TDMA! :-)

https://en.wikipedia.org/wiki/Time-division_multiple_access

eqvinox 7h ago

You can probably do phased arrays. (It might already be a phased array.)

mohaine 7h ago

Pretty sure phased array LASERs are not yet a thing.

buildbot 6h ago

I was not sure, but they are!

https://cga.anu.edu.au/research/activities/laser-beam-steeri...

https://www.darpa.mil/research/programs/excalibur

I guess in some ways even the fancy multi diode fiber lasers are phased arrays, just with the single goal of higher output power.

axus 5h ago

Looks like these are in early development and nowhere near ready like this test was.

aidenn0 6h ago

Lasers are coherent emitters; you can definitely make interference patterns with them, so I don't see why LASER MIMO wouldn't be possible, in theory.

eqvinox 6h ago

Yeah but this is research, if they're to come up somewhere, where else would it be?

voidUpdate 9h ago

If starlink satellites get laser downlink, it might work :P

cm2187 2h ago

laser downlink to one point, isn't it? Not to 300 moving aircrafts at once.

myrmidon 10h ago

I'm really curious how the tracking works in such a system, and how "bad" the beam spread is (my impression is that from the diffraction limit alone the beam has to be spread over at least a ~10m radius after travelling 36000km).

Some info on the laser itself would also be very interesting (power? wavelength?).

Really cool project though!

amelius 10h ago

> and how "bad" the beam spread is

The spread makes the tracking easier, I suppose.

TimorousBestie 8h ago

Perhaps a little, however. Different paths through the atmosphere will perturb the phase of the signal; depending on conditions not all of that ~10m beam width is going to decode with an acceptable bit error rate.

mytailorisrich 8h ago

Tracking and actuation is nothing new or particularly challenging, IMHO. It's the laser/optical part combined with throughput at that distance that is the main area of R&D, I think.

burnt-resistor 1h ago

I marvel at the ability to track a target in both directions ~40k+ km away while moving quickly (kinematic) considering atmospheric and relativistic effects.

xnx 11h ago

Impressive! I believe round trip latency would be 0.5 seconds.

1e1a 11h ago

That's ~162.5 MB in transit at any time

kevincox 9h ago

Excellent for pingfs (https://github.com/yarrick/pingfs)

kipchak 5h ago

There's a patent (2017/0280211 A1) for using this as a data storage method, and there was a company called Lyteloop trying to leverage the idea for data storage with estimations for petabytes across constellation.

arethuza 6h ago

That could you used like RAM like the delay-line memory used by early computers!

htgb 10h ago

Shouldn't it be 1000/16 = 62.5? Impressive nonetheless, of course!

1e1a 9h ago

The article says 2.6 gigabits/second which is 2,600,000,000 bits/second, 2,600,000,000b/s * 0.5s / 8 is 162,500,000 bytes, 162,500,000 / 1,000,000 is 162.5 megabytes

htgb 7h ago

Right, thanks

zppln 10h ago

Weird.

philipwhiuk 6h ago

> Because laser beams spread far less than radio waves, they provide more secure links

Basing your security on laser diffusion seems sus.

Tepix 6h ago

These beams are much harder to detect and eavesdrop upon. You increase the difficulty for a remote attacker. I wouldn't stop encrypting the data, however: The Alphasat TDP‑1 has a telescope with an 135mm aperture. The beam diameter is likely to be at least 700m wide according to the diffraction limit.

Schlagbohrer 6h ago

It's worth it as another layer of security. The beam width being so narrow means even intercepting it becomes harder. This is more relevant for down-to-earth links where the spot hitting the earth is so narrow it could be confined withing a geographically controlled area, rather than hitting an entire continent like longer wavelengths do.

kube-system 3h ago

All security is based on a combination of individually flimsy ideas

HN