A high- $Q$ niobium resonant mass gravitational radiation antenna with a superconducting parametric transducer and noncontacting readout is shown to achieve a noise temperature of about 2 mK using a zero order predictor filter. The predicted intrinsic cold damping of a parametric transducer is confirmed, along with predicted backaction limits on the sensitivity. While the antenna has the highest intrinsic $Q$ factor and lowest noise temperature ever observed in a full scale antenna, the possibility of further improvements is demonstrated.

• Received 4 April 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1908