This flight came from Cape Town and was carrying supplies and scientific equipment for the Norwegian Polar Institute Base there. And as I write, the aircraft above has just left SA airspace on its way back up to Oslo.
Cape Town is the easiest airport to use for trips to Troll, it being “just” 4350km straight down across the Southern Ocean to the ice runway there, and at this time of year, there are regular flights heading out there from a plethora of different nations. Russia and Iceland being two of the more recent ones I have spotted.
There’s a really good article on FlightRadar24 about how Troll operates here.