Following the success of UWE-1 (University of Wuerzburg’s Experimental Satellite-1) and keeping in mind the future road map for the University CubeSat program, a pressing need for a highly accurate attitude determination system for the CubeSat was expressed. In an effort to fulfill this need, two separate works were spawned to design and implement a prototype of the attitude determination system. The work was split broadly into hardware based and software based support for the envisioned system. This Master thesis describes the design, simulation and implementation of the software support for ADS (Attitude Determination System) for the UWE CubeSat. Based on the feasibility study carried out, a decision was made on the sensor suite for the attitude hardware to fulfill the requirements of the attitude determination. Followed by the feasibility study, it was required to develop a hardware prototype and a corresponding software subsystem to make use of the hardware prototype for the attitude estimation. This report describes the different attitude estimation techniques investigated, developed, results from the simulation and the final implementation of the on-board software and its variants. Two different prototypes were developed and tested. Report includes the purpose of each of the prototype and outcome of the tests. Also provided in the report is a detailed insight on the implementation of the on-board software.