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Comment by shaklee3 | Hacker News Reader

And nowhere will you see the capacity of this satellite actually advertised. My guess is it's about 1/4 of viasat-2 or Jupiter 2, which the former is flexible. There is a trade-off between how much flexibility you really need compared to on-board processing. On one extreme you have no idea where your customers are, so you do all processing on-board. This is the quantum model, I think. This comes at a huge hit to capacity.

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Initially, in 2015, they were talking about ~6-7 Gbps [1] but my guess is that the current design allows for a little bit more of throughput (8 beams @ 1 GHz/beam (max. BW) x 2 bps/Hz (?) -> 16 Gbps (?)). In any case, I would say this is a technology demonstrator satellite.

I think that their main innovation might be the software to optimally allocate power, bandwidth, spectrum, and pointing and shape of each beam so that throughput/revenue /"quality of service" is maximized, which might be run on the ground and then the "instructions" sent over the TT&C link to the satellite. I doubt that the spacecraft has the autonomy level required to conduct all these tasks onboard.

[1] https://spacenews.com/eutelsat-esa-taking-a-quantum-leap-tow...

I would find it really hard to argue that a satellite is to demonstrate technology. Nobody in this business thought this was impossible to do, but when the satellite + ground costs ~$300M, you need a way to recoup those costs. Infinite flexibility will never make up for a lack of bandwidth, and bandwidth demand is increasing faster than satellites can keep up.

I agree with you that there's no way the optimization on those things can be done on board, which means that it's likely purely the signal processing/phased array that's consuming so much power/resources that they couldn't fit more transponders to increase capacity.

I agree with you. I should have said that I think they were not looking to maximize the system throughput when designing the system, instead wanted to test this new technology. Seems the 450 kg Quantum payload has a 5.5 kW power consumption, so yeah, that phased array seems to be drawing quite a lot of power.

I am curious about your thoughts on future satellite architectures since it looks like some players are betting in full flexibility by means of DRA / phased-arrays technology (SES, SpaceX, Telesat), whereas others (Viasat) seems to be betting on fixed-spot beams + flexibility in spectrum, bandwidth, and power allocations.

Full disclosure: I work for ViaSat, so you may be able to see my biases. I could probably write about this for days.

I wouldn't say ViaSat is focusing on any of those things. ViaSat-2 was flexible in many ways, as is ViaSat-3:

https://www.viasat.com/news/going-global

"One of the greatest innovations of our Viasat-3 satellites is the ability to move resources to where customers are located dynamically."

For Telesat and SpaceX, I believe you're referring to their LEO constellations, where SES you're referring to mPOWER. LEO I believe sounds great on paper, and I don't think it will be technically impossible for SpaceX to complete. The challenge with LEOs and MEOs (mPOWER) is the cost of the ground equipment. No company to my knowledge has come close to getting the ground equipment (phased-array) to a price point which would make the business viable. Forgetting all the issues with LEO about number of launches and stranded capacity over water, I think the ground antenna will be very difficult, and it's not talked about very often.

If they find a market, such as enterprise, that's willing to pay significantly more per month for "high-speed internet", and have a fairly massive antenna on their roof, then they will succeed. I don't think that market exists since they already have fiber/cable, and getting a consumer antenna cheaper than a fixed GEO antenna will be a real challenge. I also don't think latency is a huge benefit at this point, since internet bandwidth is dominated by streaming media, which isn't affected at all by high latency. You will oftentimes see gamers complain about satellite, but in reality, they're a very tiny segment of the market, and streaming is growing faster than gaming.

I also alluded to the bandwidth demands of satellites in my other post. If you read internet usage reports, link the one from sandvine, you'll see that data usage is growing nearly exponentially, as is cord-cutting. You simply cannot launch a 10Gbps satellite these days and make money off it. If you could, the companies with 100Gbps satellites could sell the same bandwidth cheaper than you can.

My guess is that Eutelsat is really trying to take the approach of a feedback loop of demand with the satellite to try to optimize those parameters you're suggesting in real-time. Again, I think the problem with that is internet traffic on a micro level changes too frequently, but on a macro level (markets) don't change frequently at all. In other words, even the companies launching satellites with fixed capacity/beams have an extremely good idea of where their market is before they launch. Even if they're wrong by 30%, you can view that as a 30% hit to an extremely high capacity, which is still higher than the steerable one.

So in summary, I'm not optimistic on LEO, and for Quantum to be competitive, I think it would need to be in the 100Gbps range. Eutelsat already has a ~100Gbps satellite called Ka-Sat that's nearing 8 years old now, so this type of satellite from the same company makes me think it's exactly what you said -- it's an experiment since a large amount of money was free from the government. From a business point of view, it may make sense for them since they didn't pay for most of it. But the newer satellites are coming up very soon. 2019 will be somewhat quiet for new GEO launches, but I think by 2020 Quantum will seem quite underwhelming, if it isn't already today.

That 5.5 kW number - where do they get all that power? Is it all just solar?

Yes, it is all solar power.

5.5 kW is not a lot of power, modern buses for geostationary satellites (i.e., 720HP) can produce close to ~18 kW, of which ~80-90 % are normally used by the payload in a communications satellite.

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