Recent advances in the design of microsatellites have led to renewed interest in the missions that can be flown with small spacecraft and small payloads. The CubeSat platform and the Plug-and-Play concept have prompted the development of attitude determination hardware typical of larger, more sophisticated, three axis stabilized spacecraft, including miniature gyroscopes and star cameras. The X-ray Star Scanner is a new class of attitude sensor, designed to support precision spin-stabilized CubeSat missions by providing arcminute attitude accuracy in a size compatible with a CubeSat, in fact occupying less than half of a 1U CubeSat module. The scientific and technological advances necessary to make this instrument possible are in place. A robust catalog of x-ray guide stars is available through several all-sky surveys performed in x-rays. Solid state x-ray detectors and their related support electronics have been flown. The concept of using guide stars to determine the attitude of a spinning vehicle has been demonstrated using flight data. The XSS fills the need created by the CubeSat and Plug-and-Play platforms for accurate attitude determination on a spin stabilized platform provided in a small package.