The new microwave Radiometer for Atmospheric Measurements at Summit (RAMAS) has started operation at Summit station, Greenland (72°N, 38°W, 3200 m), and is now being prepared for continuous measurements. RAMAS operates in the frequency band from 265-280 GHz with an instantaneous bandwidth of currently 1 GHz. It observes the emission of thermally induced rotational transitions of a variety of stratospheric trace gases, including O₃, ClO, N₂O, HNO₃, and HCN. Tropospheric water vapor content, a major constraint on ground-based microwave radiometry, is exceptionally low at Summit station. Initial measurements and retrieved profiles are presented, demonstrating the excellent measurement conditions.