TsAGI - Tsentral'nyy Aerodinamicheskiy i Gidrodinamicheskiy Institut- central aerodynamics and hydrodynamics institute[2] – may be written CAHI as an acronym of English words
TsAGI BP-2 or BP-3 but they don't quite seem to fit the silhouette
more likely the BP-2 as the BP-3 doesn't seem to have a tailplane, maybe there were several iterations.