Large stroke and high precision electroactive single crystal and polymer actuators are desired for cryogenic passive optics such as Fabry-Perot Interferometer (FPI) and Fourier Transform Spectrometer (FTS) in NASA remote sensing missions. The results of the Phase I program have successfully demonstrated the feasibility of using electroactive single crystal and polymer actuator concepts for large stroke, high precision cryogenic actuations for passive optics. We believe this result justifies the Phase II continuation to develop electroactive single crystal and polymer actuators for cryogenic tunable FPI and FTS for remote sensing applications. In particular, single crystal stack actuators with stroke of 25 um at 77K, flextensional actuator with stroke of 100-200 um and hybrid single crystal /polymer HYBAS actuators with stroke 1-2 mm will be developed for both current cryogenic tunable FPI and future passive optics. Single crystal piezoelectrics are attractive because they exhibit 3 to 5 times the strain of conventional piezoelectric ceramics, have very low strain hysteresis, and retain excellent piezoelectric performance at cryogenic temperatures. HYBAS actuation concept exhibits significant strain improvement by combining single crystal piezoelectrics and EAP.