Radiation Shielding by Software for Reliable Electronics of Pico-Satellites

Miniaturized commercial-of-the-shelf components are very susceptible for space radiation. To provide nevertheless a reliable satellite performance, a concept based on hot redundant electronics and an “intelligent” watchdog using fault detection, isolation and recovery (FDIR) algorithms was realized. This principle proved its performance now for more than 3 years in orbit and so far no interruption was encountered. Realization with power-efficient microprocessors enables efficient implementation of redundancy concepts even at pico-satellite level (mass about 1 kg). At the example of the on-board-data-handling system (OBDH) of UWE-3 a first version of this approach is in orbit since November 2013. The microprocessors as well as the storage units are running in hot redundancy. As soon as deviations in outputs are detected, a watchdog is activated to identify by its FDIR software the faulty component. In almost real-time it directs responsibility to the correct unit and starts a recovery/rebooting process for the faulty unit. All this is handled internally in the OBDH, thus the functionality of the subsystem is not interrupted by this process and the satellite provides a continuous nominal operation. Similar approaches are transferred to the electronics of other safety critical subsystems like AOCS and power control, increasing the reliability of the overall satellite system despite just employing commercial components