[en] A gaseous large-area Cherenkov couner designed for cosmic ray detection on an artificial Earth satellite is described. The geometrical detector factor is ∼ 270 cm² x s.r. The counter is filled with freon-13 under pressure of 4 atm. and it has the relativistic factor threshold of detected particles of 12.9. The averaged device efficiency over the whole area is 98.5±0.2% in forward direction and 0.85±0.15% in reverse direction. While negligibly decreasing the detection efficiency in forward direction (down to 90%) the selection coefficient can be increased up to 350. Particles of energies below the required one for initiating Cherenkov radiation in the detector are detected with <1% efficiency. The angle corresponding to the counter efficiency reduction down to 50% is about ±12 deg