Recently, there has been a tendency to complicate real time control algorithms, to process a large amount of information from the satellite payload (optical, radar, communication systems) directly on board and to create highly informative communication lines with both ground stations and other satellites. The conditions of outer space (vacuum, radiation) impose significant restrictions on the computing capabilities of onboard equipment, which is used as an onboard digital computer complex, and lead to a significant increasing in the cost of space components. A high-performance and relatively cheap computing cluster structure of an on-board computer based on widely available single-board minicomputers is proposed, which allows distributing the computing load among several nodes and simultaneously backing up the system. As a component of a computing cluster, it is proposed to use a computing cluster system based on COTS (Commercial off-the-shelf) components, which increases performance by several orders while reducing cost. Calculations have shown that the introduction of redundancy and distribution of computational tasks makes it possible to achieve an MTBF of about 3 years, which is quite enough for the active existence of university satellites. The proposed structure of the onboard computer complex is installed on the university satellite for remote sensing of the Earth in the visible range with controlled optical magnification, after the launch of which it is planned to confirm the reliability of the results obtained in this work. An assessment of the performance and reliability of such a cluster system is given, which has shown the possibility of implementing such a system on a university satellite for Earth remote sensing.