SAGE was devised to measure the radio-chemical solar neutrino flux based on the inverse beta decay reaction, Ga + ν ν e → → e − − + Ge. The target for the reaction was 50-57 tonnes of liquid gallium metal stored deep (2100 meters) underground at the Baksan Neutrino Observatory in the Caucasus mountains in Russia. The laboratory containing the SAGE-experiment is called gallium-germanium neutrino telescope (GGNT) laboratory, GGNT being the name of the SAGE experimental apparatus. About once a month, the neutrino induced Ge is extracted from the Ga. Ge is unstable with respect to electron capture ( t 1 / 2 = 11.43 days) and, therefore, the amount of extracted germanium can be determined from its activity as measured in small proportional counters.