Official abbreviation is DSC, not STD
None of them start with ST, except Kelvin movies. Some retarded troll invented STD!
Full list: https://en.wikipedia.org/wiki/Template:Star_Trek_abbreviations
VOY's "official" abbreviation when it was in production was always "VGR", but fans simply used "VOY" instead.
And the people making STD want us to call it "DISCO", but we prefer to nickname it STD instead. Deal with it.
But if it makes you feel better to use the "official" abbreviation, then DISCO is dead!