Beomsik Kim

In this paper, we propose a reliability optimization technique for low earth orbit (LEO) satellite systems that operate in highly varying temperatures. In the proposed technique, we harden the target satellite on-board computer considering two common reliability threats, soft-error and hard-error, at the same time. Based on an existing fault-tolerant scheduling, we show how the reliability and lifetime of the system can be quantified with respect to a given error handling policy. Then, using these models, we perform extensive reliability analyses and optimizations of the hardening degree for different functional safety requirements. We implemented the proposed technique in a widely adopted real-time operating system (RTOS), Real-Time Executive for Multiprocessor Systems (RTEMS), working on a real satellite on-board computer system, GR712RC. The proposed technique enables efficient explorations of the trade-off between the soft-error reliability (failure rate), hard-error reliability (expected lifetime), and other resource utilization indicators, like power consumption or CPU utilization. In particular, the proposed technique could be successfully utilized to co-optimize the lifetime and fault-tolerance concerning the unique ambient temperature profile of LEO satellites.

Recently, thanks to the miniaturization and high performance of commercial-off-the-shelf (COTS) computer systems, small satellites get popular. However, due to the very expensive launching cost, it is critical to reduce the physical size and weight of the satellite systems such as cube satellites (CubeSats), making it infeasible to install high capacity batteries or solar panels. Thus, the low-power design is one of the most critical issues in the design of such systems. In addition, as satellites make a periodic revolution around the Earth in a vacuum, their operating temperature varies greatly. For instance, in a low earth orbit (LEO) CubeSats, the temperatures vary from 30 to −30 degrees Celsius, resulting in a big thermal cycle (TC) in the electronic parts that is known to be one of the most critical reliability threats. Moreover, such LEO CubeSats are not fully protected by active thermal control and thermal insulation due to the cost, volume, and weight problems. In this paper, we propose to utilize temperature sensors to maximize the lifetime reliability of the LEO satellite systems via multi-core mapping and dynamic voltage and frequency scaling (DVFS) under power constraint. As conventional reliability enhancement techniques primarily focus on reducing the temperature, it may cause enlarged TCs, making them even less reliable. On the contrary, we try to maintain the TC optimal in terms of reliability with respect to the given power constraint. Experimental evaluation shows that the proposed technique improves the expected lifetime of the satellite embedded systems by up to 8.03 times in the simulation of Nvidia’s Jetson TK1.