Klaus Schilling, Tristan Tzschichholz
Zentrum für Telematik, Magdalene-Schoch-Str. 5, 97074 Würzburg, Germany
Use of miniaturized commercial-of-the-shelf technology (COTS) micro-electric components for satellites was so far limited, as space radiation noise affect severely the performance by frequent reboot activity or even loss of components. Here advanced redundancy concepts in combination with Fault Detection, Identification and Recovery (FDIR) methods are used to cure this deficit.
In the context of UWE-3 the OBDH core module used an energy-efficient onboard computer for the pico-satellite UWE-3 launched in 2013. The core module is built around two tightly coupled redundant ultra-low power microcontrollers. A dynamically decided master-slave configuration enables the instantaneous master module to maintain and re-program the (even unresponsive) slave via its embedded emulation module. Thus, the core module implements special support for mutual assistance such as mutual program memory protection and recovery up to complete mutual reconfiguration in the context of fail-save in-orbit software updates. With less than 10 mW nominal power consumption the design belongs to the most efficient redundant onboard computers available for pico-satellites. The two redundant micro-controllers are supervised by an “intelligent” watchdog, detecting deviations. It is then the task of this watchdog to decide with its FDIR software in almost real-time, which is the faulty device and to transfer responsibility to the correctly performing device. The core module has proved excellent performance for more than three years of operation without any interruption of service in orbit until today.