This is a very interesting thread, and one that deserves some serious thought and comment. I have no affiliation with Outernet, and in fact I only started reading the details of their plans this week, and I think that the comments that Arxos makes are very interesting and in many cases are broadly sound from a technical perspective. However, I also think - based on what I have read about Outernet - that he seems to have missed the point in a number of areas. My own thoughts, in response to the comments made by Arxos, are the following:
Well, maybe, and who knows. But surely that’s a risk for those providing funding to assess? My own view is that any project that gets ordinary, non-specialist people thinking about engineering and technology can’t be altogether a bad thing.
I don’t think that Outernet have ever claimed anything else. There has been an awful lot of media and press hype, however, with the impression being given that this would be a global, unregulated, broadband, WiFi, Internet-in-the-sky - which it isn’t.
Don’t write off one-way, broadcast data services by the way. I’m old enough to remember the introduction of the BBC’s “Ceefax” Teletext service in the mid-1970s. The difference between having no ‘on-line’ access to news and information and having something is really significant. What Outernet seems to be proposing is clearly not a real-time service. It’s a one-way “transmit-and-store-locally” service, which is quite a different thing.
Agreed. 100% true. But on the basis of the previous point, were Outernet to be implemented as a LEO system, this is far less of a problem. I don’t know what data rate could be broadcast to terrestrial receivers, but even if each territory only saw a few passes each day (say 20 minutes of coverage, per receiver, per day) then even a relatively low bitrate signal could transfer a sizeable amount of data. For example, supposing that 500 kbit/s of usable data could be achieved (and I fully acknowledge that designing the link budget to support such bit-rates with terrestrial receivers of a sensible size will be a challenge and will mean that the satellites could probably not be based on a standard cubesat bus, which would not provide enough power) then you could in principle move 600 Mbit of data to each receiver, each day. it seems to me that this is enough data to allow users to receive (over time, not on-demand) the daily news, information, documents, etc. that Outernet is aiming to broadcast.
If it is being suggested that this service will be receivable on a cellphone then I agree, that doesn’t make any sense at all. But from what I have seen, those claims seem to arise from the media hype not from Outernet. On the other hand, it is perfectly possible to imagine a small user terminal with a low gain whip antenna receiving the transmissions. Whether that works or not comes down to the link budget, and whether or not there is enough power available on the satellite to ensure that the received carrier-to-noise is high enough to permit the data to be received and demodulated. I’ve not seen any link budgets, but I’ve no doubt at all that viable links can be designed on paper. Whether or not such links can be supported in the real World by the available power on the satellite is, as I’ve already said, going to be a challenge. But if the satellite is not a cubesat then it may be possible (I would like to see some link budgets to be able to assess this further).
I would also note that - if the link budget can be made to work - then a low-gain, non-directional antenna doesn’t need to track the satellite. Because it is low gain it can “see” the whole sky, so tracking is not necessary,
Again, agreed. But two points need to be made here. First is that because of the non-real-time “transmit-and-store-locally” model, it is not necessary to have a constellation of hundreds of satellites so that every territory has one or more satellites always visible in the sky all the time. This is not a Teledesic or a Skybridge. It’s only necessary to have enough satellites so as to ensure the minimum number of passes per day per territory to support the daily data transmission requirements of the system.
Secondly, as I have mentioned above, I would not expect this to be implementable using standard cubesat technology. But that doesn’t mean that each satellite has to cost tens or hundreds of millions. Look at what Skybox Imaging (recently acquired by Google) has achieved. They have developed some impressive satellites for somewhere in the region of $2M to $5M each.
No they won’t. As I’ve already said, they will not need global, real-time coverage. Moreover, they will not need to mesh the satellites together either. Each satellite is essentially an independent, store-and-forward, data broadcaster. Once the dataset is loaded onto the satellite it can go on transmitting it, continuously, allowing each user to (over time, several passes, maybe even several days) to store their own local copy.
This one I agree with. I don’t see how a January 2015 launch date is achievable. Maybe a low-power technology demonstrator cubesat could be built and launched in a short time-scale, but I’m pretty sure that the larger satellites as mentioned above will take a while to design, build and launch. But what the heck? Haven’t we all hyped our projects to get a bit of attention? I would hope that, as the project develops, more realistic plans and estimates would be made.
Well, perhaps. But I don’t think that terrestrial-based radio gets around either the “digital divide” or the “state censorship” issues. A sizeable proportion of people in the World live outside the range of terrestrial infrastructure, and I don’t see that being built any time soon. Moreover, terrestrial infrastructure will always be in the control of the state on whose territory it is based. Outernet seems, to me, to be offering a possible solution to both these problems. Sure, it’s not the only way of doing things, but so what? It is an interesting approach, and satellites certainly have the advantage of supporting global ubiquitous coverage outside the direct reach of state control (except for the state under whose authority the satellites are operated - so best get that one right!).
This seems to me to completely misrepresent what Outernet are trying to achieve, for reasons explained above.
Isn’t this what Outernet have already implemented, by way of their test platform on GALAXY-19 and HOTBIRD-13? That said, I don’t see it as a viable, long-term solution, simply because the barriers to entry are too high (Ku-band dish, LNB, DVB receiver, etc.).
Interesting idea! A kind of “pirate radio” for data. Technically it would work I’m sure, but many states have implemented laws allowing them to board and shut down broadcasting transmitters on vessels, even in international waters. I would not personally want to be crewing the ship in the waters off of North Korea or China.
Well yes, maybe. But from what I have read, Outernet certainly doesn’t have $12bn to spend, and anyway, a two-way, global, real-time data constellation seems to be well outside the scope of what Outernet is trying to achieve.
Same comment as for previous point.
Agreed, absolutely. But see above as to why I don’t think that this project is likely to be based on cubesats.
The way that I interpret it is that the Ku-band GEO implementation is essentially a technology demonstrator. It’s a way of getting a service up-and-running very quickly. A kind of proof-of-concept. As I have mentioned above, however, I don’t think that a Ku-Band GEO implementation is viable long-term, because it is just too hard to access for non-technically qualified people. Moreover, in oppressive states which limit citizen access to news and information, access to and use of large dish antennas tends also to be strongly regulated - and a 75cm Ku-band dish is hard to hide!
For that reason, I think that - as a concept at least - a lower frequency (sub 1 GHz), LEO constellation, based on (relatively) cheap satellites (not cubesats) must be the way forward. Whether it can be made to work or not, and at a price that permits it to go ahead, frankly, I don’t know yet. But conceptually it is interesting and I’d want to see a lot more data before writing it off.
My view is that interesting technical proposals ought to be taken seriously, developed, enhanced and - if the technologies and the finances work out - implemented. This is especially true when the project is, as I understand Outernet to be, a not-for-profit, aiming to do something good for the World.
Neither do I (see above)! Glad to end on a point of agreement.