This Letter describes a collaborative TGV (Telescope Germanium Vertical) study of the double beta decay of 48 Ca with a low-background and high sensitivity Ge multi-detector spectrometer. The results of T 1/2 2νββ =(4.2 +3.3 −1.3 )×10 19 years and T 1/2 0νββ >1.5×10 21 years (90% CL) for double beta decay of 48 Ca were found after processing experimental data obtained after 8700 hours of measuring time, using approximately 1 gramme of 48 Ca. The features of a TGV-2 experiment are also presented.