Apparently the Russian Glonass satellites are programmed in Modula-2 [1] which seems like a wild choice.
1) https://en.wikipedia.org/wiki/Modula-2#Russian_radionavigati...
In 1999 I used Modula-2 for my first computer science/programming languages exam at university. The environment was a bit like Turbo Pascal 3.0, though with a more complete language (TP3 had no modules/units) and library, comparable perhaps to TP5.
Well, back in the 1980's up to early 90's, Modula-2 enjoyed a mild success in Europe.
Given that it was available in 1978, and the satellites launched in 1982, it seems a plausible choice like any other, given the computing ecosystem at the time.