I follow the Aireon development with quite some professional interest...
So far, I get the feeling that some companies are literally gambling "Vegas style", big time. Can't blame them (unless it's all taxpayer money), satellite based definitely has potential. Especially for oceanic airspace and it may for the first time allow some kind of surveillance data competition in a certain block of airspace (without having to own ground based surveillance assets). Who wouldn't want to be among the early movers and on a "sexy" project?!
But there are also serious doubts and concerns, of course...
General Aviation must be extremely careful and lobby in order not to become a playing ball in a really large scale experiment of specific commercial interests...
First, it looks like the whole thing was a "late in the game" trick idea by/with iridium to sell/fill some spare satellite capacity with a novel application. Before any ops concepts were written, separation standards evaluated etc... A classic money/engineering driven approach that is prone to hit problems if not approached from the operations angle at the same time...
They were practically launching satellites before anything was sorted out or even studied beyond high level concepts. With the hope[sic!] that it would eventually work out and perform. Ironically, launched by [awesome!] SpaceX, which ultimately may anyway have the better platform/solution for such an ops concept with their starlink constellation... ;-) [I wouldn't be surprised if we'll eventually mount next gen starlink digital transponders & radios on our airplanes...]
Not only could that cover the surveillance part but more importantly the communications part as well! Multiple times more redundant and with less latency. But they have bigger fish to fry right now, I guess...
Aside from transatlantic traffic, I have yet to see proof that Aireon can reliably track all targets in a dense continental airspace, including all low flying piper cubs etc... Hence the push in Canada for diversity (lots of "vegas money" coming from there). If you only have a partial surveillance picture, you have a useless picture, at least in the sense of ATC.
Anyone else noticed the gradual shift of their offerings on their website more into the direction of business analytics / flow management and such? ;-) Drifting away from the surveillance angle which was dead center in the beginning...
Another big problem is the business case. Unless you can massively reduce minimum separation and as a result move lots more traffic (assuming demand comes back the same or better post-covid!) and/or replace radar/WAM ground based surveillance infrastructure, the whole thing isn't much more than a "me too" affair...
The infrastructure gamble, by the way is somewhat a shared problem with the U.S. ADS-B approach, just finding out now that turning off radars is not going to happen as quickly as imagined...)
In order to reduce minimum separation you have to convince a lot of bright mathematicians at ICAO level which are really good at collision risk modelling. Problem there is, surveillance is only one part of the equation. And through lots of gradual improvements (0.5 degree lateral tracks, ADS-C longitudinal etc...), the position uncertainty has already been reduced quite a bit, so the improvements possible through Aireon aren't as crass of a magnitude as it may initially seem like. But better it may be.
Then, the biggest problem is RCP (required communication performance). Knowing where flights are is only half the game. You have to be able to make something out of it, and do so reliably. Called controller and communication intervention buffer. And for that, from what I've gotten to read so far, the Aireon concept appears to be pretty much nil, as a result the big bets on improvements appear to be more hope than reality so far...
I would really slow-roll the diversity topic or else make them pay for it!
It's their business, not ours...
I believe in WAM and radars anyway. And for that, our simple basic mode-s transponders are going be sufficient for quite some time!