I doubt your going to fit a ground control unit in your raft... At least not a VSAT unit. The best option, albeit expensive is the BGAN service pictures on that page linked above. The speed of BGAN is such that you'll be able to get outlook or other applications to function, but it's a metered service. So you'll pay per megabyte transmitted. Its can be frustratingly slow at times as well, especially knowing the "meter is turning".
The other issues is that inmarsat BGAN is based on a geostationary satellite and therefore has a consistent look angle of about 30-45 degrees to the south-southwest. This will prove to be a challenge in the canyon itself. If you can do limit your activity to those times when you'll have this look angle, you'll save a lot of frustration trying to get online. I use an iPhone app (such as dishpointer) to know when I have a good angle and no obstructions.
There are a couple of other options than BGAN. The next band to try is in the low-earth orbit (LEO) and uses the L-Band as well. These satellites are a constellation of cross-linked satellites, which pass over head. These are things like globalstar or iridium. The ones that hand held sat phones use. There are a couple of options here, but I like iridium the best. The network is not a broadband based network, rather it's circuit switched. That said, it does have some options for low speed data. The best option in this class, IMO, is the iridiumGo. While it's not speedy, it does have some options for checking email, getting weather, and light web browsing using optimized software. You might not get outlook going on your laptop, but you can use optimized versions of software that can work with gmail to download only headers. From there you can pick which messages to download. Iridium data channels are going to be minute-based and the speed of an old dial-up modem. They also have a voice app that can function as a sat phone from the iPhone or iPad.
You'll have a better chance getting a signal from a LEO sat down in the canyon, though it might fly out of view while the next one comes in. Given the others that have used sat phones down there, this is probably a better option than BGAN.
There are a number of service providers that have customized applications to work over low-speed sat links for overlanding. Check out OCENS. They have someone that comes on expo from time to time to talk about their applications and services.
If you just need to be able to two-way message, post to Facebook, Twitter, and have SOS capability, then I recommend inreach.
For me, I run the iridiumGo with an iPad mini. I forward my important email to gmail and fetch it there. You'll want to turn off other applications that are accessing over wifi, or they'll kill the link. In fact, I'd delete all non-essential apps so they aren't running in the background. I also carry an inReach for position and status reporting. Both the Go and inReach have SOS capability. InReach is probably a better tool for that since it's a personal device you'd have in your pocket.
Source: I'm a satellite tech specialist with a SAR team. I've run satcom from VSAT all the way down to RF line of site communications. Day job, I work for a satellite equipment manufacturer.
