RESEARCH POSTER PRESENTATION DESIGN © 2012

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INTRODUCTION

What is the problem?

The ISS SpaceCube Experiment Mini (ISEM) is designed to

increase computing power on board the International

Space Station. Its field programmable gate arrays (FPGAs)

occasionally experience upsets known as single-event

upsets (SEUs), which are caused by a single particle hitting

sensitive electronics and freeing an embedded particle.

METHODS

1.* Upsets from 2014 (solar maximum) and 2017 (near

solar minimum) were located using ISS Tracker (Figure 1).

2. The SAA was simulated using the AE9/AP9/SPM

Radiation Environment Model (Figure 2).

3. The proportion of upsets likely caused by the SAA was

estimated (Table 2).

4. Space weather analysis was conducted to determine

whether an SEP event, radiation belt enhancement (RBE),

or geomagnetic storm (GST) was a plausible cause of each

upset that did not occur in the SAA.

5.** The proportion of upsets sufficiently close in time to

each space weather event was compared to the proportion

of the entire year that was sufficiently close in time to

each space weather event (Table 3).

6.** The temporal distribution of the upsets was tested for

uniformity (Figure 3).

* Solar maximum and (near) solar minimum were used to

distinguish between various space weather events.

** Steps 5 and 6 were only done for 2014 because 2017 did

not have enough upset data for reliable analysis.

RESULTS CONCLUSIONS

The proportion of upsets that occur in the SAA is

significantly higher than the proportion of time that the

ISS spends in the SAA. As a result, there is clear evidence

that the SAA causes upsets. We can estimate that

roughly 23% of all ISEM upsets and roughly 71% of ISEM

upsets that occur in the vicinity of the SAA are caused

by the SAA.

The lack of significant correlation between enhanced

space weather activity and ISEM upsets casts doubt on

the hypothesis that any of the space weather events

studied here (SEPs, GSTs, and RBEs) cause the upsets.

The temporal distribution of the upsets outside the

SAA fits a Poisson distribution reasonably well,

suggesting that uniform random or essentially random

processes, such as GCRs, cause many of the upsets.

There was very little difference between the numbers of

upsets per FPGA in 2014 and 2017. This is not enough to

discredit the hypothesis that GCRs are a significant

cause of the upsets, but it is surprising, as the frequency

of GCRs, while roughly constant in the short run, varies

significantly over the solar cycle.

A significant limitation of this analysis is the very small

amount of data: the only available upsets were 62

upsets from one FPGA in 2017 and 190 upsets from three

FPGAs in 2014.

REFERENCES

Galactic Cosmic Rays. (2012, May 11). Retrieved July 16, 2018, from

https://helios.gsfc.nasa.gov/gcr.html

Ginet, G.P., et al. (2013). AE9, AP9 and SPM: New Models for Specifying the

Trapped Energetic Particle and Space Plasma Environment. In: Fox, N.,

Burch, J.L. (Eds.), The Van Allen Probes Mission. Springer, Boston, MA.

I.S.S. Tracker. (n.d.). Retrieved July 18, 2018, from

http://www.isstracker.com/historical

Mewaldt, R. A., Davis, A. J., Lave, K. A., et al. 2010, ApJL, 723, L1

Primary Cosmic Rays. (n.d.). Retrieved July 16, 2018, from

http://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Primary.htm

SpaceCube: A Family of Reconfigurable Hybrid On-Board Science Data

Processors. (2017, April 4). Retrieved July 2, 2018, from

https://spacecube.nasa.gov/

Zheng, Y. (2018). Space Weather Impacts on Satellites/Space Assets

[PowerPoint slides]. Retrieved from

https://ccmc.gsfc.nasa.gov/RoR_WWW/SWREDI/2018/REDI2018_template_

SWx_Impacts_Sat_final_f.pdf

ACKNOWLEDGMENTS

Sujay would like to thank Dr. Yihua Zheng for her mentorship and the staff

of the Community Coordinated Modeling Center (CCMC) for introducing him

to the field of space weather. He would also like to thank the Catholic

University of America (CUA) for its support through the Science and

Engineering Summer Internship (SESI) program. Finally, he would like to

thank Thomas Flatley for supplying and clarifying the ISEM upset data and

fellow forecasting intern Keyan Gootkin for helping him plot the SAA.

1Massachusetts Institute of Technology (MIT), 2NASA GSFC Code 674

Sujay Kazi1, Yihua Zheng2

Analysis of ISS SpaceCube Experiment Mini Upsets

Figure 1: A map of the 62 upsets that occurred on one FPGA of the SpaceCube experiment in 2017. The 10 upsets that occurred over South America and the 4 upsets that occurred over the south Atlantic ocean are likely caused by the SAA, while the others have less predictable causes.

Figure 2: A map of the flux intensity of the trapped particles at the height of the ISS orbit (about 400 km). The flux is close to zero everywhere other than the SAA because the inner radiation belt is well above the ISS orbit altitude everywhere else on the planet.

Figure 3: The year 2014 was split into 73 segments of 5 days each, and the frequency of the number of upsets outside the SAA in each period was tested against a Poisson distribution.

FURTHER RESEARCH

Future analysis would include a much greater amount of

upset data from many years and more information

regarding the nature and severity of each upset.

In particular, examining the frequency of upsets over

several years could be a way to test the hypothesis that

GCRs are a significant cause of the upsets.

Table 2: The numbers and proportions of upsets that occurred in the vicinity of the SAA in 2014 and 2017 were used to estimate what fraction of upsets are likely caused by the SAA.

Why should we care? Space weather can affect anything we send into space. For

instance, SEPs are a hypothesized cause for the loss of

contact with STEREO-B (a satellite launched in 2006 to help

provide a full view of the Sun) in October 2014, and

astronauts staying on the ISS for extended periods of time

have had cases of cancer caused by high-energy radiation.

Understanding the levels of threat various space weather

phenomena pose to electronics and people in space will be

necessary for future space missions, such as the James

Webb Space Telescope and a future trip to Mars.

What are the suspects? SEUs tend to be caused by space weather events including

solar energetic particles (SEPs) and galactic cosmic rays

(GCRs), as well as more static presences such as the South

Atlantic Anomaly (SAA), a region where the inner radiation

belt crosses the altitude of the ISS due to the shape of the

Earth’s magnetic field. These are shown below in Table 1:

Table 3: The proportion of 2014 upsets in the temporal vicinity of a GST, SEP event, or RBE is shown to be not significantly greater than the proportion of the whole year of 2014 in the temporal vicinity of each of these events. This means that it is plausible that these upsets had other causes and were close to these events simply by chance.