This paper describes the design, fabrication, characterization, and satellite integration of a miniaturized two axis sun sensor which has been used in the attitude control system of the Spanish nano-satellite NANOSAT-1B. This device is made of four silicon photodiodes monolithically integrated in a crystalline silicon substrate, protected by a transparent cover glass assembled on the same silicon die against space radiation damage. The sensor fabrication combines standard silicon processing technology with a high performance solar cell fabrication process. The sensor, including electronics and mechanical and electrical interfacing with the satellite, has a small size (3 cm 3 cm) and low weight (24 gr.), with a sun field-of-view greater than 􀀀 with an angle accuracy better than 0.15 . Three of these sensors have already been integrated in the NANOSAT-1B platform that has been successfully launched in July 2009.