DEVELOPMENT OF MICROSATELLITE ATTITUDE DETERMINATION AND CONTROL SYSTEM
Since the beginning of the 21 <sup>st</sup> century the vector of spacecraft development began turning toward the class of microsatellites. These spacecrafts have a mass up to 100 kg. This direction of evolution is due to the development of electronics and miniaturization of satellite devices. A prime example is the microsatellite Chibis-M, production of IKI RAN, having a mass of 36 kg. It has a huge functionality. Chibis-M is equipped with a three-axis attitude determination and control system that provides precision of 0.1° Further development and increasing range of objectives which can be solved by micro-satellites require higher precision of orientation, as well as expanding of functionality. For this purpose, SPUTNIX Ltd in cooperation with IKI RAN and KIAM are developing attitude determination and control system for satellites with a mass from 10 to 100 kg. Initially the system is designed for satellite platform TabletSat, developed by SPUTNIX Ltd, but can be adapted to other microsatellites. The system consists of a controlling unit, a set of sensors: a magnetometer, sun sensor, angular velocity sensor, star tracker, a set of control elements: a series of electromagnetic torquers, several flywheels, control moment gyroscope. An important part is the software. As a basis for constructing of the platform architecture TabletSat the principle of unification of mechanical, electrical and information standards is taken, thereby providing flexibility when designing microsatellite. Different combinations of sensors, control elements and algorithms able to satisfy a wide range of possible requirements for orientation. For example, the satellite may be left uncontrolled and roughly determine the orientation, the satellite may be stabilized by the rotation, or the satellite can provide three-axis stabilization with an accuracy of 1° down to 10ʺ. Development of attitude determination and control system is based on the experience gained in the design of such a system for microsatellite Chibis-M. So the facility for semi-natural modeling of attitude determination and control system which consists of air bearing, magnetic field simulator, sunlight simulator and which was used for Chibis-M attitude determination and control system tests will be used for testing of the new system. Due to the issue that new attitude determination and control system includes star sensor, the stand will be supplemented with the starry sky simulator. Also air bearing with increased capacity and movable sunlight simulator are developed. Stand functional will be extended with software system of moments of inertia and center of masses determination. Thus, the general principles of attitude determination and stabilization design are presented, their basic characteristics are given. Capable modes provided by attitude determination and stabilization system are presented, as well as their accuracy. Also the structural elements of the facility for semi-natural tests, expanding its functionality and allowing to test of developed system orientation are described.