Future NASA planetary science missions have very limited access to solar power and therefore reducing the cryocooling system power input is even more critical than for earth-orbiting satellites. On this program, Creare proposes to develop and demonstrate an innovative Stirling cryocooler that efficiently produces refrigeration at 30 K and rejects heat at about 150 K. A key component of the proposed cryocooler, its regenerator, will be optimized on this program to obtain high efficiency over this operating temperature range. The innovation is a regenerator fabricated by a unique process to enhance its heat capacity near its target cooling temperature and, therefore, increase the overall thermal efficiency of the cryocooler. The proposed cryocooler is built on technologies developed for commercial Stirling cryocoolers that are extremely compact and efficient while rejecting heat at 300 K. In Phase I, we proved the feasibility of our approach by demonstrating the regenerator fabrication process and its high heat capacity near 30 K, and showing the high thermal efficiency of the 30 K cooler by design and analysis. In Phase II, we will fabricate a Stirling cryocooler that incorporates the regenerator with high heat capacity, optimize the cooler, and deliver the cryocooler to NASA for further performance characterization at the end of the program.