Space borne observation requires extremely high resolution systems with large dimensions. The design of such systems implies associating sensing and actuation systems to insure a highly stable positioning of optical components. However, the currently used PZT materials for piezoelectric actuation show strongly diminished strain at cryogenic temperatures. This work explores the performances of PMN-xPT piezoelectric materials at cryogenic temperatures. Temperature dependence of PMN-xPT ceramics is compared with hard PZT (PZT-4) and soft PZT (PZT5H) ceramics from RT to 10 K. PMN-PT tetragonal compositions exhibit stable piezoelectric constant in the 250-100 K range. The highest values of piezoelectric constant are observed for PMN-38PT in the 200-50 K range. All ceramics exhibit decreasing performances versus cooling temperature. This behaviour is attributed to a "freezing out" of extrinsic contributions to piezoelectricity [12] but is also due to a contribution of quantum effects [13, 14]. The mechanical quality factor (Q m) increases very quickly from 50 K to 10 K for all samples. This fact could be due to low relaxation processes at very low temperatures.