[FtrPilot]

My guess is the Russian Corvette Ivanovets was deployed to Ozero Donuzlav (Lake Donuzlav) in western Crimea as a stop-gap SAM site.

Lake Donuzlav on Google Maps

The RU surface to air assets are stretched to the breaking point.

Comments welcome.

[BeauBo]

Wikipedia for that class of Corvette, seems to say that it has just a few MANPADS for Air Defense:

Armament
4 × P-15 Termit/SS-N-2 Styx or 4 × P-270 Moskit/SS-N-22 Sunburn or 16 × Kh-35 Uran/SS-N-25 Switchblade anti-ship missiles.
1 SA-N-5 SAM (1x4) MANPADS air defence missiles
1 × 76 mm AK-176 dual purpose main gun
2 × AK-630 30 mm gun or 1 × CADS-N-1 Kashtan CIWS (close-in weapon system) for air defence

[BeauBo]

Oops, and one S-200 HIMAD missile (SA-N-5)