Observations of Long-Term Radiation-Induced Effects in High-Density Commercial Memories on- Board Alsat-1

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1 Observations of Long-Term Radiation-Induced Effects in High-Density Commercial Memories on- Board Alsat- Youcef Bentoutou and El-Habib Bensikaddour Satellite Development Center POS Ilot T, Bir-El Djir, Oran, Algeria Tel.: +, Fax: +, Abstract This paper presents a review of a long-term study on radiation effects in non-hardened high density memory devices operating within the main on-board computer system of the Algerian microsatellite Alsat- in Low Earth Orbit (LEO). A statistical analysis of single-event upset (SEU) activity is presented for commercial SRAM devices, and their response to extreme solar events shows SEU rate significant increases correlated with highenergy protons (E > MeV). Ground based neutron monitor data are used to illustrate the long-term relationship between galactic cosmic rays and Alsat- upsets. The short-term effects of energetic solar particles are illustrated with space environment data from GOES-. The Alsat- observed SEU rates are compared to the predicted rates based on ground test data and environment models. The prediction results are in good agreement with in-flight data. Keywords Radiation Effects; SEU, Memory Fault tolerance; Inflight data. T I. INTRODUCTION he space environment beyond Earth is flooded with radiation composed of high-energy particles from the Sun, belts of protons, electrons and ions collected within Earth s magnetic field and Galactic Cosmic Rays (GCR) arriving from beyond the Solar System. Radiation has always been an unseen enemy for satellites and can have serious effects on satellite operation that range from unimportant ones to the catastrophic failure of a vital satellite subsystem such as the On Board Computer (OBC). Special radiation hardened components offer reliable and high performance solutions for satellite applications. Even so, radiation remains one of the leading causes of satellite anomalies and as technology advances, the risk increases. For these reasons it is important to understand the space radiation environment so that reliable satellite subsystems can be designed at a reasonable cost. In Low Earth Orbits (LEO), it is well known that one of the adverse effects of space radiation on spacecrafts is a transient error known as Single Event Upset (SEU) []-[]. Bit-flips caused by SEU are a well-known problem in computer memory chips and error detection and correction techniques have been an effective solution to this problem []-[]. SEU induced data error propagates through the run-time operational flight software causing erroneous outputs from a flight-critical computer system, such as a command error affecting thruster firing, or system crash. The first Algerian Microsatellite Alsat- experienced several important Solar Particle Events (SPE) causing OBC crashes and forcing flight software reloads. Observation of SEU in dynamic and static RAMs on-board low earth orbit satellites has lead to various analyses [7]-[]. The in-orbit data have shown that such memory devices are likely to exhibit both single-event single-bit upsets and singleevent multiple-bit upsets (MBU) []. Non-hardened highdensity Static Random Access Memories (SRAMs) were observed to be more resilient to SEU than the low-density SRAMs []. Over the past decade, arrays of Samsung commercial-offthe-shelf (COTS) memory devices operating within the main computer OBC-8 of Alsat- were monitored for SEU and MBU for the whole spacecraft life-time. Recently, in-orbit observations of SEU and MBU in these memory devices have been presented from November to August []. The observed SEU flight data provide useful information on the behavior of SEU sensitive COTS memory devices. This paper aims to present a follow-up of the evaluation and statistical analysis of SEU and MBU activities in commercial memories onboard Alsat- and to correlate these activities with extreme solar cosmic ray particle events and long-term changes in the radiation environment. II. ALSAT- MISSION AND ON-BOARD MEMORIES Alsat- is the first Algerian Earth observation mission using a small satellite in LEO []-[]. The spacecraft is part of a wider international collaboration to launch the first disaster monitoring constellation of Earth observation satellites. The primary goal of the mission is to provide daily imaging worldwide for the monitoring and mitigation of natural and man-made disasters as well as dynamic Earth observation. Alsat- was launched into a 8 km sun-synchronous orbit in November. This microsatellite carries speciallydesigned Earth imaging cameras which provide -meter

2 resolution imaging in spectral bands (green, red, and near infrared) with an extremely wide imaging swath of km on the ground that enables a revisit of the same area anywhere in the world at least every days with just a single satellite []. The Alsat- main On-Board Computer (OBC) is an Intel 8C8EX based system that was designed, built and tested at Surrey Satellite Technology Limited (SSTL), a company owned by EADS-Astrium at the University of Surrey in Guildford, UK. The OBC plays a dual role for Alsat-, acting as the key component of the payload computer as well as the command and control computer for the microsatellite. It has also been adopted by several other satellite projects []. The OBC is a general purpose computer for space applications. It features Mbytes of program memory which is protected by error detection and correction (EDAC) and Kbytes of firmware storage EPROM. The EDAC is implemented using Triple Modular Redundancy (TMR) with voting logic, requiring Mbytes in total. The board also supports multiple data inputs and can store a maximum of 8 Mbytes of data. This memory is normally referred to as the Ramdisk. Compared to the program memory there is no hardware protection on the Ramdisk, instead a double-error correcting modified Reed-Solomon RS (,) code is used []. The encoding and decoding process is executed entirely in software. Data are transferred in -byte blocks, which comprise bytes of information, three RS code bytes and one byte is used to give the capability of double byte correction. The RS (,) code can correct any number of bit-errors affecting no more than two bytes per block. Thus, three or more bytes would have to be affected to cause a "severe" error under this scheme []. III. IN-ORBIT OBSERVATIONS Since Alsat- is placed in a LEO with an inclination of 98 at 8 km altitude, elevated levels of radiation caused by the lack of atmosphere increase the probability of SEU. A SEU is a non-destructive error which usually affects logic cells in such a way that it can cause a bit in a memory device to change logic states. This phenomenon is caused by a false charge created by the transit of a single ionizing particle through a memory chip. There are various methods of error detection and correction, but the most commonly used solutions are based on Hamming and Reed-Solomon codes, and TMR []. Satellite Development Center's (SDC) microsatellite Alsat- has provided an in-orbit operational test-bed for COTS memories since. The preliminary results of an 8-year study and analysis (-) of the behavior of the on-board memories in the LEO radiation environment have been reported previously in terms of the influence of the LEO environment on SEU rate []. Similar results have been reported by Surrey Space Center [8]-[] and NASA [] for SRAMs operating within dedicated experimental payloads. This paper presents Radiation-induced errors collected onboard the Alsat- main OBC during the whole mission lifetime and particularly during extreme solar cosmic ray particle events. The Ramdisk memories are based on eight Samsung SYS 8, parts of Mbytes each in size (total memory of Mbytes). Table I summarizes the observations from the Alsat- main computer M-Bytes Ramdisk. From these final observations, the correct average SEU rate is SEU/day in 8 memories of M-Bytes each. The mean SEU rate at Alsat- s orbit is.7-7 SEU/bit/day, where 98.% of these SEUs cause single-bit upsets,.% cause double-byte upsets, and the remaining SEU result in multiple-bit, and severe upsets. Most of the Single-Byte Multiple-bit Upsets (SMU) are double-bit upsets. Double-byte errors are events which affect two bytes. Severe errors are due to single-event multiple-bit upsets affecting bits spread across more than two bytes. The severe (uncorrectable) error-rate of these memory devices is. - severe error/bit/day when using the double-error correcting modified Reed-Solomon RS (, ) code []. System monitored TABLE I SEU OBSERVATIONS FOR ALSAT- OBC 8 RAMDISK Memory EDAC code R-S (, ) Memory size M-bytes Hybrid SYS8RKXLI-7 ( M 8-bit) Device Samsung SEC KM8BLT-L K 8-bit SRAM Observation period 8 days November 9 August Bits monitored 8 Total number of upsets 888 No. of Single-bit upsets 9 (98.9%) No. of double-byte upsets 9 (.%) No. of severe upsets 7 (.9%) No. of Multiple-bit upsets (.87%) Figs. - show the daily number of single-bit, multiple-bit, double-byte, and severe upsets per day, respectively. From these figures it is clear that the majority of single event effects cause single-bit upsets. During Solar minimum conditions, the upset rates correspond to about 8 single-bit upsets per day, multi-bit upset every days, severe upset every days, and double-byte upset per day. These rates correspond to about single-bit upsets per day, multi-bit upset every days, severe upset every 9 days, and double-byte upsets every two days during solar maximum conditions. Solar maximum corresponds to the period and solar minimum to the period 7. Most of the spikes present in Fig. correspond to solar flares. Although in the sunspot activity cycle was on its maximum phase, the number of the registered SEUs is low between November 9 and May. A maximum of five () multiple-bit and severe upsets were recorded on July 7, 7. A maximum of nine (9) double-byte upsets were recorded on June, 9. The dates of these events correspond to high latitude regions. One could think that these severe upsets were created by single ions hitting two memory devices in their path through the OBC.

3 8 7 Single-bit upsets/day Severe upsets/day 9// 7// 8// 7/7/ // // // // /8/ 8// // 7// /7/ // // // // /8/ 8// 7//7 7//7 /7/7 /9/7 //7 //8 //8 9/8/8 8//8 //9 //9 //9 /9/9 //9 // // /7/ 9// 7// 8// 7/7/ // // // // /8/ 8// // 7// /7/ // // // // /8/ 8// 7//7 7//7 /7/7 /9/7 //7 //8 //8 9/8/8 8//8 //9 //9 //9 /9/9 //9 // // /7/ Fig.. Daily Single-bit upset rates on Alsat- Ramdisk from November 9 to August Fig.. Daily severe upset rates on Alsat- Ramdisk from November 9 to August Multiple-bit upsets/day 9// 7// 8// 7/7/ // // // // /8/ 8// // 7// /7/ // // // // /8/ 8// 7//7 7//7 /7/7 /9/7 //7 //8 //8 9/8/8 8//8 //9 //9 //9 /9/9 //9 // // /7/ Fig.. Daily multiple-bit upset rates on Alsat- Ramdisk from November 9 to August Double-byte upsets/day // 7// 8// 7/7/ // // // // /8/ 8// // 7// /7/ // // // // /8/ 8// 7//7 7//7 /7/7 /9/7 //7 //8 //8 9/8/8 8//8 //9 //9 //9 /9/9 //9 // // /7/ Fig.. Daily double-byte upset rates on Alsat- Ramdisk from November 9 to August There are three primary sources of natural particle radiation in the space environment [7]: Galactic cosmic rays have their source outside the solar system; Energetic solar particles are accelerated into the near Earth environment by solar flares; and Energetic particles in the radiation belts are trapped by closed field lines in Earth's magnetosphere. During the observation period, 888 SEU were accumulated from 9// to /8/ on the Alsat- Ramdisk memories. The majority of SEUs are low latitude upsets that are due to satellite passages through the South Atlantic Anomaly (SAA) []. There are three classes of SEUs: low-latitude SAA upsets, high-latitude upsets due to Galactic Cosmic Rays (GCR), and upsets due to Solar Particle Events (SPE). The majority of SEU occurs only within the South Atlantic Anomaly (SAA), i.e. in bursts lasting for ~- minutes each orbit and the other SEU are induced by the Galactic Cosmic Rays in the high latitude regions []-[]. The number of upsets occurring outside the SAA under quiet-time conditions (i.e. no solar particle events) is so small by comparison. Fig. illustrates the relationship between SEU rate evolution, Galactic Cosmic Rays (GCR), and solar activity. The GCR are represented by ground-based neutron monitor data from Moscow, Russia. The provided data are daily averages of hourly counts. The solar activity is represented by the sunspot number. It is clear from this figure that the galactic cosmic radiation has an inverse relationship with the solar cycle variation, in which the flux is maximum at solar minimum and minimum at solar maximum. Moreover, the envelope of the Alsat- upsets clearly follows the modulation of the GCR. This figure shows several important Forbush Decreases, the most notable in October and January. This figure also shows two extraordinary giant Ground Level Events (GLEs) that occurred on January,, and December,, respectively. GLEs occur when solar cosmic rays with sufficient energy and intensity increase radiation levels on the surface of Earth. The spikes in January and December reach 77 and SEUs per day respectively.

4 which caused 79 upsets in the sensitive memory devices of Alsat-. 8 / / / / / /7 /8 /9 / // // 9/8/ // 9// 7// 8// 7/7/ // // // // /8/ 8// // 7// /7/ // // // // /8/ 8// 7//7 7//7 /7/7 /9/7 //7 //8 //8 9/8/8 8//8 //9 //9 //9 /9/9 //9 // // /7/ Counts/Hr Fig.. Daily SEU rates on Alsat- Ramdisk from November 9 to August 8 Moscow Neutron Monitor.E+ Solar Particle Induced SEUs Proton > MeV integral flux Sunspot Number / / / / / /7 /8 /9 / Integral proton flux (#/cm^ s).e+.e+.e+ Proton > MeV integral flux Proton > MeV integral flux / / / / / /7 /8 /9 /.E+ 8// 9// // 7// 8// // // 7// 8// // Fig.. SEU rate evolution associated with galactic cosmic rays, represented by neutron monitor data, and the solar activity, represented by the sunspot number. The neutron monitor data are daily averages of hourly counts. The sunspot numbers are monthly values. A. Extreme solar cosmic ray particle events and their influence on the SEU rate at Alsat- altitude Solar Particle Events (SPE) at LEO can occur throughout the solar cycle but are most frequent in solar maximum years. SPE have a significant impact on the upset rates. A high sensitivity to high-energy solar particles has been observed on Alsat- exposed to the solar particles during solar activity. Fig. shows the daily SEU counts on Alsat- from November 9 to August. From this figure, it can be seen that major events have induced an increased SEU number on the Alsat- memories. As a consequence, the main OBC experienced several crashes forcing flight software reload. Other solar events have been observed during this period but only the events with a significant increase of high energy protons have induced increased SEU rates on the Alsat- memories. Major SPE caused upsets to occur in most of the spacecraft memory systems. The most significant event being that of 9th October Fig. 7. SEU rate increase with proton spectrum composition of the main observed SPEs Environmental data have been analyzed in order to correlate them with the observed SEU rate increases. Fig. 7 shows the SEU rate increase with the proton spectrum composition of the large observed SPEs (October, January, and December ) as given by the measurement from the NOAA GOES- Spacecraft. High-energy protons have an impact on the SEU rate during large SPEs. Fig. 8 shows a comparison between the number of upsets during large SPE with the corrected integral proton fluxes (E > MeV) for these days. It is clear from this figure that during these events, the SEU rate increases are well correlated to proton flux with energies greater than MeV. SAC-C and Orbview- flight data have also shown a correlation of the SEU rates during SPE with the proton fluxes > 8 MeV [], and > MeV [], respectively.

5 Number of SEUs/day // 9// // 7// 8// // // Solar Particle Induced SEUs Proton > MeV integral flux 7// 8// // Fig. 8. SPE induced SEU rate evolution associated with daily averages of integral proton fluxes (E > MeV) measured by GOES- ) Halloween events The October period of saw one of the most energetic solar flares and coronal mass ejections of any solar cycle. These events came to be known as the Halloween Events and included several X-class flares, radiation storms and geomagnetic storms [8]. Three of these CMEs that occurred on October 8, 9 and November were associated with X7, X, and X8 flares, respectively. The global effects were wide-ranging, impacting power grids, airline flights, and spacecraft operations. The November CME was the most energetic flare which was not Earth-oriented and thus only resulted in high-latitude auroras. Alsat- experienced the X7-class flare ejected on 8 October and a G-level geomagnetic storm the next two days. The whole sequence of events occurred from 8 to October. During these events (in days) 7 upsets have been observed on the OBC memory. Fig. 9 plots the daily SEU rates on Alsat- memories during the Halloween events. The SEU rate jumped considerably with the occurrence of these major events. A total of 798 SEUs were registered on October 9. As expected, the upset rate is well correlated with solar cycle and SPE. Table II summarizes the SEU rate observed during the Halloween Events. 8 7 Proton > MeV integral flux (#/cm^ s sr) TABLE II INFLUENCE OF HALLOWEEN EVENTS ON SEU RATES ON-BOARD ALSAT- Date October 8 October 9 Total number of upsets No. of Single-bit upsets 79 8 No. of double-byte upsets 8 No. of severe upsets No. of Multiple-bit upsets October ) Impacts of the January extreme SPE on SEU rate Although in the sunspot activity cycle was on its decreasing phase approaching minimum, the Sun had a phase of very high activity between and January. In this period of time, the solar active region NOAA AR 7 produced five powerful solar flares. In association with this major solar activity several pronounced variations in the ground-level cosmic ray intensity were observed [9]. The fifth of these flares, an X7-rated flare produced energetic solar cosmic rays that caused an important increase in the SEU rates on-board Alsat-. Fig. plots the daily SEU rates on Alsat- memories during this solar cosmic ray particle event. 77 upsets were observed on January,. As expected, the upset rate is well correlated with this major solar flare. Table III summarizes the SEU rate observed during this SPE // // // // 7// 8// 9// // // // // // Fig.. Daily SEU rates on Alsat- Ramdisk during the extreme Solar event on January // // // // // // // 7// 8// 9// // // // // // // // Fig. 9. Daily SEU rates on Alsat- Ramdisk during the Halloween Events Date TABLE III SEU RATES DURING THE JANUARY SPE January 9 January Total number of upsets 7 77 No. of Single-bit upsets 7 77 No. of double-byte upsets 7 No. of severe upsets No. of Multiple-bit upsets January ) Other Solar flare events and their impact on SEU rate at Alsat- altitude After these two extreme solar cosmic ray particle events, Alsat- experienced another SPE on December. From the recordings of GOES (Geostationary Operational Environmental Satellite) satellites, six () solar flares were observed on 7 December and three () solar flares were

6 detected on December. Our analysis shows a maximum increment of the effective SEU rate due to solar cosmic rays in the high latitude regions. Fig. shows the daily SEU rates on Alsat- memories during this solar cosmic ray particle event. A maximum SEU rate of 9 and upsets were recorded on December 7 and, respectively. These upset rates are well correlated with GOES solar flare indicator during solar flares. Table IV summarizes the SEU rate observed during this SPE. CREME 9 worst day model was used. The results are shown in Table VI. Cross Section (cm /dev) E+ E- E- E- // // // 7// 9// // // // 7// 9// // // // 7// 9// // Fig.. Daily SEU rates on Alsat- Ramdisk during the December SPE Date TABLE IV SEU RATES DURING THE DECEMBER SPE December 7 Total number of upsets 9 No. of Single-bit upsets No. of double-byte upsets No. of severe upsets No. of Multiple-bit upsets December Cross Section (cm /dev) E- 8 LET (Mev.cm /mg) Fig.. SEU Cross section for the KM8. E- E- E-7 E-8 E-9 8 Proton Energy (Mev) IV. COMPARISON OF ALSAT- FLIGHT SEU RATES TO PREDICTIONS Predictions for the heavy ion and proton induced upset-rate were made using the ground test results found in the literature [] and fitting a Weibull three-parameter curve to the data points. The OMERE [] software was used to calculate the upset rates, based upon a uniform shielding of g/cm for the spacecraft. The sensitive thickness is generally considered equal to µm []. Weibull fitting parameters of ground test data used for the predictions are presented in Table V. TABLE V CROSS-SECTION DATA FITTING PARAMETERS USED FOR THE PREDICTIONS Weibull fit parameters Heavy-ion data Proton Data Width (W). MeV cm /mg. MeV cm /mg On set (S). MeV cm /mg.8 MeV cm /mg Power.8 MeV cm /mg.99 MeV cm /mg Plateau. cm /device.9 - cm /device Figs. and show Heavy ion and proton SEU cross section curves for the KM8, respectively. Solar minimum and solar maximum models were used for the background environment (CREME 9 [] for GCR and AP8 [] for trapped protons). For the SEU rates during SPE, the Fig.. Proton induced SEU cross section for the KM8 SRAM TABLE VI PREDICTED HEAVY-ION AND PROTON UPSET RATES AND FLIGHT OBSERVED RATES Environment Predicted SEU rates Observed SEU rates Background (SEU/bit/day).8x - (solar min).7x - (solar max) (SEU/bit/day).7x -7 (max yearly average).x -7 (min yearly average) SPE.87x - (worst-day).7x - (October 8, ).97x - (October 9, ).x - (October, ).8x - (January, ).x - (December, ) The theoretically estimated SEU rate using the solar minimum models underestimates the actual flight SEU rates due to the background environment by a factor of. During these worst case solar minimum conditions, trapped proton and GCR fluxes are highest. On the other hand, as about 8% of the SEUs occur in the SAA, an underestimation of the SEU rate was expected. This discrepancy is preliminarily due to simplifying assumptions used by the AP8 model that underestimates the actual trapped proton fluxes at low altitudes and simplifications used in describing the device architecture.

7 The calculated SEU rate with the AP8 solar maximum model underestimates the actual SEU rates by a factor of. This underestimation may be due to different factors: SEU characterization, shielding assumptions, and sensitive volume thickness assumptions. The predicted SPE rate and the observed data agree to within a factor of., for the largest SPEs of October 9, and January,, the theoretical predictions being lower than the observations. For the observed SPEs of October 8 and,, the predicted rate and the observed data agree to within a factor of. For the case of the December, SPE, the calculated SEU rate with the CREME 9 SPE worst day model overestimates the actual SEU rates by a factor of.. The ratio of the predicted SEU rate to the observed rates varies from. to.. CREME 9 SPE worst day model gives a best-case estimation of solar particle fluxes. The October 989 event is one of the largest SPE ever observed; therefore, a good estimation was expected. V. CONCLUSION This paper has presented a review of a long-term study on radiation effects in non-hardened high density memory devices operating within the main on-board computer system of Alsat- in LEO. In-orbit observations of single and multiple event upsets are presented for the period between November and August. SEU rate s correlation with solar cycle and solar events has been found as expected. Several large SPE occurred during the Alsat- mission and their impact on COTS memories has been observed. During large solar events, the SEU rate increases are well correlated to high-energy protons (E > MeV). The flight data has shown that is important to have accurate information about the solar particle flux, and the shielding to study the effects of large SPE. The worst case for the KM8 -Mb SRAM devices has been observed for the October Halloween events and a maximum rate increase was measured during these events. The Alsat- observed SEU rates have been compared to the predicted rates based on ground test data and standard environment models. The theoretically estimated SEU rate using CREME 9 cosmic ray model and AP8 trapped proton model underestimates the actual flight SEU rates due to the background environment by a factor between and. During large SPE, the predicted SPE rate and the observed data agree to within a factor of.. VI. ACKNOWLEDGMENTS We acknowledge the NMDB database ( founded under the European Union's FP7 programme (contract no. 7) for providing neutron monitor measurements, and the NOAA's National Geophysical Data Center for providing GOES data. [] M.S. Hodgart, Efficient Coding and Error Monitoring for Spacecraft Digital Memory, Int. J. Electronics, vol. 7, no., pp. -, 99. [] M.S. Hodgart and H. Tiggeler, A (,8) Error Correcting Code (t=) for Critical Memory Applications, in proc. Data Systems In Aerospace, Montreal, Canada, May -,. [] C. I. Underwood, J.W. Ward, C.S. Dyer, and A.J. Sims, Observations of Single-Event Upsets in Non-Hardened High-Density SRAMs in Sun- Synchronous Orbit, IEEE Trans. Nucl. Sci., vol. 9, no., pp , Dec. 99. [7] A. J. Tylka et al., Single events upsets caused by solar energetic heavy ions, IEEE Trans. Nucl. Sci., vol., pp. 78 7, Dec. 99. [8] C. I. Underwood and M. K. Oldfield, Observed Radiation-Induced Degradation of Commercial-Off-The-Shelf (COTS) Devices Operating in Low-Earth Orbit, IEEE Trans. Nucl. Sci., vol., pp. 77 7, Dec [9] C. I. Underwood, The Single-Event-Effect Behaviour of Commercial- Off-The-Shelf Memory Devices A Decade in Low-Earth Orbit, IEEE Trans. Nucl. Sci., vol., pp. 7, Dec [] C. I. Underwood and M. K. Oldfield, Observations on the Reliability of COTS-Devise-Based Solid State Data Recorders Operating in Low- Earth Orbit, IEEE Trans. Nucl. Sci., vol. 7, pp. 7, June. [] R. Harboe Sorensen, E. Daly, F. Teston, H. Schweitzer, R. Nantallo, P. Perol, F. Vanderbussche, H. Dzitko, and J. Cretolle, Observation and analysis of single event effects on-board the SOHO satellite, IEEE Trans. Nucl. Sci., vol. 9, pp., June. [] D. Falguere, D. Boscher, T. Nuns, S. Duzellier, S. Bourdarie, R. Ecoffet, S. Barde, J. Cueto, C. Alonzo, and C. Hoffman, In-fight observations of the radiation environment and its effects on devices in the SAC-C polar orbit, IEEE Trans. Nucl. Sci., vol. 9, no., pp , Dec.. [] C. Poivey, J. L. Barth, K. A. LaBel, G. Gee, and H. Safren, In-Flight Observations of Long-Term Single-Event Effect (SEE) Performance on Orbview- Solid State Recorders (SSR), in Proc. IEEE Radiation Effects Data Workshop, Monterey, CA, Jul., pp. 7. [] C. Boatella, G. Hubert, R. Ecoffet, and S. Duzellier, ICARE On-Board SAC-C: More Than 8 Years of SEU and MCU, Analysis and Prediction, IEEE Trans. Nucl. Sci., vol. 7, no., pp. 9, August. [] M. Bekhti, M. Sweeting, and W. Sun, Alsat-: The first step into space for Algeria, in Proc. rd IAC and World Space Congress, Houston, TX,, pp. -9. [] Y. Bentoutou, A follow-up of in-orbit observations of radiationinduced effects in commercial of the shelf memories on-board Alsat-, Advances in Space Research, vol. 8, pp. 7-, May. [7] D. C. Wilkinson, S. C. Daughtridge, J. L. Stone, H. H. Sauer, and P. Darling, TDRS- Single Event Upsets and the Effect of the Space Environment, IEEE Trans. Nucl. Sci., vol. 8, no., pp. 78-7, Dec. 99. [8] W. B. Manchester IV, et al., Three-Dimensional MHD Simulation of the October 8 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations, Astrophysical Journal, 8, vol. 8, no., pp. 8-, 8. [9] R. Bütikofer, E. Flückiger, L. Desorgher, and M. Moser, The extreme solar cosmic ray particle event on January and its influence on the radiation dose rate at aircraft altitude, Sci. Total Environ., vol. 9, pp. 77 8, 8. [] S. Petit, Etude des Méthodes de Prédiction de Taux d erreurs en orbite dans les mémoires: nouvelle approche empirique, Ph.D. Dissertation, ONERA, Toulouse, France,. [] OMERE Software V. [Online]. Available: [] A. J. Tylka et al., CREME9: A revision of the cosmic ray effects on micro-electronics code, IEEE Trans. Nucl. Sci., vol., pp., Dec [] D. M. Sawyer and J. I. Vette, AP-8 Trapped Proton Environment for Solar Maximum and Solar Minimum, NSSDC/WDC-A-R&S, 7-, NASA/Goddard Space Flight Center, Greenbelt, MD, Dec REFERENCES [] Y. Bentoutou, A Real Time Low Complexity Codec for use in Low Earth Orbit Small Satellite Missions, IEEE Trans. Nucl. Sci., vol., no., part, pp. -7,. [] Y. Bentoutou, M. Djaifri, A.M. Si Mohammed, Design and Implementation of a quasi-cyclic Codec for Random Access Memories on board Alsat-, Acta Astronautica, Elsevier Science, vol., no. -, pages: 9-9, March/April. [] Y. Bentoutou, A Real Time EDAC System for Applications On-Board Earth Observation Small Satellites, IEEE Trans. Aero. Elec. Sys., vol. 8, no., Jan..

SIMULATION OF SPACE RADIATION FOR NANOSATELLITES IN EARTH ORBIT *

Romanian Reports in Physics, Vol. 64, No. 1, P. 302 307, 2012 SIMULATION OF SPACE RADIATION FOR NANOSATELLITES IN EARTH ORBIT * M.F. TRUȘCULESCU 1,2, O. SIMA 1 1 University of Bucharest, Physics Department,