The paper deals with a 3U+ CubeSat Satellite for Land and Maritime Surveillance equipped with a 12 MP panchromatic optical payload and AIS (Automatic Identification System) bent -pipe capabilities. It is a technology demonstrator, designed to operate as a s tand-alone spacecraft. Design, development and integration of this microsatellite are an important e xamp le of cooperation between industrial world and academic world. " OHB Italia Spa", a lead ing company in Italy, part of a cluster of European firms owned by OHB SE, is the principal project designer and developer. The company established a fruitful cooperation with University of Rome "Sapienza" for Nanosats development. The S5Lab o f "Sapien za" University of Ro me is involved in a number of projects for the design and development of CubeSats as main research activity. The dev elopment strategy is based on the use of commercial components (COTS), with the exception of the key technologies, namely the payloads: telescope, optical sensor and the AIS, which are designed by the company. The University is responsible for the design, development and assembly of the On-Board Computer (OBC) Software, as well as providing support during integration and testing phases. The OBC software architecture aims to robust ness and reliability, exploits classical approaches for embedded systems programming and implements software redundancies to prevent the mission loss in case of data corruption and components failure. This paper describes the mission objectives, requirements and satellite internal configuration, mainly focusing on the On-Board Computer Software architecture.