Spirit Gyroscope is a radiation-hardened Interferometric fiber optic gyroscope (IFOG)-based system designed specifically for satellite-pointing applications. The superb low noise performance of the IFOG allows for precise jitter-free pointing with superior 15-year continuous operation. Typical noise performance is better than 0.0003 deg/radical hr with in-run bias better than 0.002 deg/hr (1 sigma). Accelerometers are optionally available. The I/O interface is Mil-Std-1553B. Input power options include 28V and 70Vdc.