• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.10-16
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• 2008

Generally, the satellite circling round in a low orbit goes through Van Allen belt connecting with the magnetic fold, in which electronic components are easily damaged and shortened by charged particles moving in a cycle between the South Pole and the North Pole. In particular, Single Event Upset(SEU) by radiation could cause electronic device on satellite to malfunction. Based on the idea mentioned above, this study considersabout SEU effect on the On-board Computer(OBC) of STSAT-1 in the space environment radiation, and shows algorithm to cope with SEUs. In this experiment, it also is shown that the repetitive memory read/write operation called memory wash is needed to prevent the accumulation of SEUs and the choice for the period of memory wash is examined. In conclusion, it is expected that this research not only contributes to understand low capacity of On-board Computer(OBC) on Low Earth Orbit satellite(LEOS) and SaTReC Technology satellite(STSAT) series, but also makes good use of each module development of Korea Multi-Purpose Satellite(COMPSAT) series.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1589-1599
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• 2017

Field programmable gate arrays (FPGAs) are getting more attention in safety-related and safety-critical application development of nuclear power plant instrumentation and control systems. The high logic density and advancements in architectural features make static random access memory (SRAM)-based FPGAs suitable for complex design implementations. Devices deployed in the nuclear environment face radiation particle strike that causes transient and permanent failures. The major reasons for failures are total ionization dose effects, displacement damage dose effects, and single event effects. Different from the case of space applications, soft errors are the major concern in terrestrial applications. In this article, a review of radiation effects on FPGAs is presented, especially soft errors in SRAM-based FPGAs. Single event upset (SEU) shows a high probability of error in the dependable application development in FPGAs. This survey covers the main sources of radiation and its effects on FPGAs, with emphasis on SEUs as well as on the measurement of radiation upset sensitivity and irradiation experimental results at various facilities. This article also presents a comparison between the major SEU mitigation techniques in the configuration memory and user logics of SRAM-based FPGAs.

• ETRI Journal
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• v.29 no.1
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• pp.124-126
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• 2007

In this letter, we study the impact of single event upsets (SEUs) in space or defense electronic systems which use memory devices such as EEPROM, and SRAM. We built a microcontroller test board to measure the effects of protons on electronic devices at various radiation levels. We tested radiation hardening at beam current, and energy levels, measured the phenomenon of SEUs, and addressed possible reasons for SEUs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1174-1180
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• 2011

Field Programmable Gate Array(FPGA)s are replacing traditional integrated circuits for space applications due to their lower development cost as well as reconfigurability. However, they are very sensitive to single event upset (SEU) caused by space radiation environment. In order to mitigate the SEU, on-board computer of STSAT-3 employed a triple modular redundancy(TMR) and scrubbing scheme. Experimental results showed that upset threshold energy was improved from 10.6 MeV to 20.3 MeV when the TMR and the scrubbing were applied to the on-board computer. Combining the experimental results with the orbit simulation results, calculated bit-flip rate of on-board computer is 1.23 bit-flips/day assuming in the worst case of STSAT-3 orbit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.417-422
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• 2010

When memory devices are exposed to space environments, they suffer various effects such as SEU(Single Event Upset). Memory systems for space applications are generally equipped with error detection and correction(EDAC) logics against SEUs. In this paper, several error detection and correction codes - RS(10,8) code, (7,4) Hamming code and (16,8) code - are analyzed and compared with each other. Each code is implemented using VHDL and its performances(encoding/decoding speed, required memory size) are compared. Also the failure probability equation of each EDAC code is derived, and the probability value is analyzed for various occurrence rates of SEUs which the STSAT-3 possibly suffers. Finally, the EDAC algorithm for STSAT-3 is determined based on the comparison results.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.6
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• pp.519-524
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• 2007

The OBC(on-board computer) of a satellite which plays a role of the controller for the satellite should be equipped with preventive measures against transient errors caused by SEU(single event upset). Since memory devices are pretty much susceptible to these transient errors, it is essential to protect memory devices against SFU. A common method exploits an error detection and correction code and additional memory devices, combined with periodic memory scrubbing. This paper proposes an effective memory scrubbing scheme for the OBC of STSAT-2. The memory system of the OBC is briefly mentioned and the reliability of the information stored in the memory system is analyzed. The result of the reliability analysis shows that there exist optimal scrubbing periods achieving the maximum reliability for allowed overall scrubbing overhead and they are dependent on the significance of the information stored. These optimal scrubbing periods from a reliability point of view are derived analytically.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1440-1446
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• 2008

In this paper, a novel TMR (Triple Modular Redundancy) memory structure is proposed using state feedback control of asynchronous sequential machines. The main ability of the proposed structure is to correct the fault of SEU (Single Event Upset) asynchronously without resorting to the global synchronous clock. A state-feedback controller is combined with the TMR realized as a closed-loop asynchronous machine and corrective behavior is operated whenever an unauthorized state transition is observed so as to recover the failed state of the asynchronous machine to the original one. As a case study, an asynchronous machine modelling of TMR and the detailed procedure of controller construction are presented. A simulation results using VHDL shows the validity of the proposed scheme.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.109-118
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• 2001

KITSAT-1, launched in 1992, passes through Inner Van Allen Radiation Belt in which high energy Protons cause single event upsets(SBUs) in the main memory of KITSAT-1 OBC(On-Board Computer) 186. The present paper compares SEU data from the OBC186 with the AP-8 model of NASA/NSSDC using the Chi-Square method to estimate the SEU threshold energy. Shielding effect by the satellite body has been taken into account to model the proton fluxes at the position of OBC186, and SEUs recorded during the high solar activities have been removed to avoid the spurious result. The result shows that the SEU threshold energy of the main memory of KITSAT-1 OBC186 is estimated to be about $110{pm}10MeV$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.1-5
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• 2008

This paper analyzes on the radiation effect of silicon solar cells in a low Earth orbit satellite by using high energy electron beams. Generally, the satellite circling round in a low orbit go through Van Allen belt, in which electronic components are easily damaged and shortened by charged particles moving in a cycle between the South Pole and the North Pole. For example, Single Event Upset (SEU) by radiation could cause electronic devices on satellite to malfunction. From the ground experiment in which we used the high energy electron beam facility at Knrea Atomic Energy Research Institute (KAERI), we tried to explain sun sensor degradations on orbit could he caused by high energy electrons. While we focused on the solar cells used for light detectors, We convince our research also contributes to understand the radiation effect of solar cells generating electric powers on satellites.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.131-145
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• 1994

The Cosmic Ray Experiment (CRE) is one of the modules flown on board the KITSAT-1 satellite and consistes of two sub-systems: the Total Dose Experiment (TDE) and the Cosmic Particl Experiment(CPE). The purpose of CRE is to characterize the space radiation environment as encountered by an Earth-orbiting spacecraft. KITSAT-1 orbit is dominated by the inner Van Allen radiation belt. This region has a large population of high energy protons which contributes significantly to both long-term and transient radiation effects. The data shows that the inner Van Allen radiation belt is very stable and the solar activity influences the CPE, TDE data and SEU(Single Event Upset) rates. The result also shows that much larger high energy particle flux is recorded than the predictions of the CREME code.