... The experimental data obtained using Cherenkov light of EAS reflected from the snow surface of the Big Alma-Ata Lake (Kazakhstan) are presented. ... The balloon-borne measurements in the energy range 10 15 -10 20 eV are planned. ... SPHERE detector array was elaborated for balloon-borne experiment [3-5]. ... SPHERE detector was situated on the 160 m high mountain ledge nearby the B.Alma-Ata lake (2500 m above sea level) to detect Cherenkov light reflected from the snow surface of the lake. ...