Progress in the development of cryogenic detectors for GNO

An improvement of the statistical and systematic uncertainty beyond the level achieved in GALLEX is an essential prerequisite for GNO. As major contributions to these errors are associated with the detection of the EC-decay of ⁷¹Ge in miniaturized gas counters, low temperature calorimetric detectors might provide a promising alternative for a later phase of GNO. We report first results achieved in measurements of the EC-decaying isotopes ⁷¹Ge and ³⁷Ar with cryogenic calorimeters.