Over the past 15 years many organizations have researched the use of Static-Random Access Memory (SRAM)-based Field-Programmable Gate Arrays (FPGAs) in space. Although the components can provide a performance improvement over radiation-hardened processing components, random soft errors can occur from the naturally occurring space radiation environment. Many organizations have been developing methods for characterizing, emulating, and simulating radiation-induced events; mitigating and removing radiation-induced computational errors; and designing fault-tolerant reconfigurable spacecraft. Los Alamos National Laboratory has fielded one of the longest space-based FPGAs experiments, called the Cibola Flight Experiment (CFE), using Xilinx Virtex FPGAs. CFE has successfully deployed commercial SRAM FPGAs into a low-Earth orbit with Single-Event Upset (SEU) mitigation and was able to exploit effectively the reconfigurability and customization of FPGAs in a harsh radiation environment. Although older than current state-of-the-art FPGAs, these same concepts are used to deploy newer FPGA-based space systems since the launch of the CFE satellite and will continue to be useful for newer systems. In this article, we present how the system was designed to be fault tolerant, prelaunch predictions of expected on-orbit behaviors, and on-orbit results.

Softcore processors are an attractive alternative to using radiation-hardened processors in space-based applications. Unlike traditional processors however, the logic and routing of a softcore processor are vulnerable to the effects of single-event upsets (SEUs). This paper applies two common SEU mitigation techniques, TMR with checkpointing and DWC with checkpointing, to the LEON3 softcore processor. The improvement in reliabilty over an unmitigated version of the processor is measured using three metrics: the architectural vulnerability factor (AVF), mean time to failure (MTTF), and mean useful instructions to failure (MuITF). Using configuration memory fault injection, we found that DWC with checkpointing improves the MTTF and MuITF by over 35x, and that TMR with triplicated input and outputs improves the MTTF and MITF by over 6000x.

Reconfigurable computing systems remain difficult to use and program. One way to increase design productivity for these systems is through reuse of previously developed and verified intellectual property (IP) cores. This paper presents CHREC XML, a XML schema that facilitates IP reuse by encapsulating the details of reusable IP cores at multiple levels of abstraction. This schema is independent from any design language or tool and can be used by any tool to understand many details about the interface of a reusable circuit. An IP integration tool was also created based on this schema to demonstrate the ease of IP reuse when cores are described in this meta-data description. This IP integration tool allows a designer to easily select and integrate IP cores from a variety of languages/tools and automatically run the appropriate tools to generate the cores in a form usable by downstream implementation tools.

Summary form only given. We describe novel methods of exploiting the partial, dynamic reconfiguration capabilities of Xilinx Virtex 1000 FPGAs to manage transient faults due to radiation in space environments. The on-orbit fault detection scheme uses a radiation-hardened reconfiguration controller to continuously monitor the configuration bit streams of 9 Virtex FPGAs and to correct errors by partial, dynamic reconfiguration of the FPGAs while they continue to execute. To study single event upset (SEU) impact on our signal processing applications, we use a novel fault injection technique to corrupt configuration bits, thereby simulating SEU faults. By using dynamic reconfiguration, we can run the corrupted designs directly on the FPGA hardware, giving many orders of magnitude speed-up over purely software techniques. The fault injection method has been validated against proton beam testing, showing 97.6% agreement. Our work highlights the benefits of dynamic reconfiguration for space-based reconfigurable computing.

FPGAs are an appealing solution for space-based remote sensing applications. However, in a low-Earth orbit, FPGAs (field programmable gate arrays) are susceptible to Single-Event Upsets (SEUs). In an effort to understand the effects of SEUs, an SEU simulator based on the SLAAC-1V computing board has been developed. This simulator artificially upsets the configuration memory of an FPGA and measures its impact on FPGA designs. The accuracy of this simulation environment has been verified using ground-based radiation testing. This simulation tool is being used to characterize the reliability of SEU mitigation techniques for FPGAs.