At least a few years ago, IceCube had it's own Iridium modems, in addition to a small pool of them for the station at large. Latency is very high, bandwidth is very low. It's much better when you can send an email over Iridium to ask for help from a human on the other side, than to SSH and do it yourself.

I think the situation now is a lot better than it was, but a few years ago, most of the day there was no connectivity except Iridium. Most communications satellites are in orbits that don't take them near the poles, with Iridum being the obvious exception.

Related: https://en.wikipedia.org/wiki/GOES_3 was an amazing piece of the South Pole infrastructure for several years. There was a period every year where the Earth would eclipse GOES-3 - the batteries onboard were long dead - so the satellite would power down and everyone just sorta crossed their fingers and hoped it came back online with the right orientation and with enough electronics going so that we could keep using it. Bandwidth wasn't great, but it was quite reliable especially considering that it was launched in 1978.

iridium is available all the time but very slow and the scarce bandwidth is not prioritized for incidental ssh access. The problem is that there are a lot of people / experiments at Pole.