From UNISAT-3 to UNISAT-4

The microsatellite UNISAT-3, completely designed, manufactured and operated in orbit by a team of students, researchers and professors of Gruppo di Astrodinamica dell’Università degli Studi “La Sapienza” (GAUSS) at the Scuola di Ingegneria Aerospaziale of the University of Roma “La Sapienza”, is the third microsatellite of the UNISAT program, which has the main goal of providing “hands-on education”, where the students can complete their instruction by practicing on a real, even if small, space program. UNISAT-3 was launched on June 29th 2004. This paper describes the microsatellite UNISAT-3, its main subsystems, the building procedures set up using mainly industrial, not space qualified, materials. Moreover ground test campaign carried out on UNISAT-3, in particular tests concerning the structure and photovoltaic subsystems, are described. The fourth satellite of the UNISAT program, UNISAT-4, has been designed and almost ready for final integration, with launch scheduled on December 2005. The lessons learned and preliminary results from operation in orbit suggested some improvements to be implemented on the satellite bus. In particular it has been realized that significant enhancement could be achieved concerning the photovoltaic system. UNISAT-4 photovoltaic system is based on monocrystalline terrestrial grade silicon solar arrays extensively tested on previous satellites and triple junction solar cells which required the development of a custom assembling technology deeply discussed in the paper.