On August 13th, two vessels from the Russian Navy entered the Mediterranean Sea: the Yelnya tanker (Altay class) and the Kildin spy ship (Moma class).
While not certain, it is highly likely that these two ships, bound for Tartus, are traveling not too far apart from each other. Periodically (approximately once a day), the Yelnya tanker sends a low-frequency radio message to Russian Navy stations.
This is the Morse code message released by the tanker today at 14:06 CEST:
It contains some weather information and transmits the ship’s position and speed (35.8N 17.3E Heading South East at 6-10 Knots).
This enables us to track the Russian unit, currently in the central Mediterranean, on its course toward Syria. By the end of the week, at the latest the beginning of next week, both units are expected to reach Tartus.