The facility was recently upgraded and expanded by Russia to provide Syria and Iran with situational awareness of the Middle East. After the upgrade, which took from January to mid-February, it reportedly covered the whole of Israel and Jordan and a large part of Saudi Arabia. According to the report, the upgrade was a reaction to Iranian concern of the facility being too much focused on the Syrian Civil War, neglecting espionage on Israel. New equipment and additional personnel was thus added to the base. As only static and worn out looking sensors were captured  , the more modern equipment and Russian personnel were undoubtedly evecuated days or weeks before.
It is unknown if the facility is named Center S ('S' for Syria or special), it is known there's at least one other Russian-Syrian SIGINT facility around, named Center S-2. A badge commemorating the ten year anniversary of this other spy facility can be seen below.
The Russian operator of Center S was the Osnaz GRU, responsible for radio electronic intelligence within Russia's Armed Forces. Although not much is known about this unit, its logos can be seen below. "Части особого назначения" - Osnaz GRU and "Военная радиоэлектронная разведка" - Military Radio Electronic Intelligence.
Various photos on the wall inside the captured facility once again emphasise the Russian involvement in the Middle East, showing even a map of Israeli Armed Forces bases and units. Other photos detail Russian personnel working at and running the center, as well as highlight a visit by Kudelina L.K., Counselor to the Minister of Defence of Russian Federation.
''Начальники "Центра-С" - Chiefs of Center S. The six lines beneath reveal the ranks of the Russian chiefs, their names and dates when they commanded the Center. All six seem to have rank of Полковник - 'Colonel'. Surnames are not readable.
''Рабочий визит начальника ГУ МВС ВС РФ'' - Visit by the chief of the Main Directorate of International Military Cooperation of the Armed Forces of Russian Federation.
"Карта радиоэлектронной обстановки" - Radio electronic situation map.
Russian espionage network in Syria exposed as more facilities are uncovered