Carta is Latin and Italian for "paper" and is Spanish and Portuguese "letter". In English it takes the form "card" or "chart". Most of its uses pertain to its meaning as "paper", "chart", or "map", for example in Magna Carta.

Definition of 'carta'\n\n 1. a formal document from the sovereign or state incorporating a city, bank, college, etc, and specifying its purposes and rights. 2. ( sometimes capital) a formal document granting or demanding from the sovereign power of a state certain rights or liberties.

You'll need all three pieces of evidence to crack this one: The Coded Message To Qasim, the Numbers Station Broadcast and the Frontpage of the Observer Newspaper. Once you have all three, you can get the code and the passphrase, each of which is required to decrypt the floppy disk.