Analysis of GEO spacecraft anomalies: Space weather relationships

Abstract

[1] The authors welcome the comment from J. E. Mazur and T. P. O'Brien [Mazur and O'Brien, 2012] on our recently published study [Choi et al., 2011]. In our paper, we investigated the geostationary Earth orbit (GEO) satellite anomalies archived by Satellite News Digest (SND) during 1997-2009 in order to search for possible influences of space weather on the anomaly occurrences. There were good relationships between geomagnetic activity (as measured by the Kp index) and anomaly occurrences of the GEO satellites; the satellite anomalies occurred mainly in the midnight-to-morning sector, and the anomalies were found more frequently in spring and fall than in summer and winter. A comparison of the SND data with data from Los Alamos National Laboratory satellites showed that low-energy (<100 keV) electrons exhibit behavior similar to that of spacecraft anomalies and implied that the spacecraft charging may be a primary contributor to the GEO spacecraft anomalies reported on the SND Web site (http://www.sat-index.co.uk). [2] Mazur and O'Brien [2012] point out that some anomalies used in our analysis were not obviously caused by space weather effects. In fact, we intentionally used all of the GEO satellite anomalies listed on the SND Web site in order to exclude a subjective selection effect. Our event list, chosen from the SND database, represented major satellite anomalies that had significant financial impacts. There were numerous minor satellite anomalies reported from many agencies, and we want to emphasize that their tendency was similar to that of our event list. While the number of events may not be large enough to analyze local time dependence, when the anomalies reported by SND from 2010 to 2011 (indicated in Figure 1 by star symbols) are included, it is very clear that the anomaly occurrences are more frequent at nighttime than during the daytime. [3] Mazur and O'Brien [2012] also mention the relationship between GEO satellite anomalies and charging effects. Internal charging may be concerned with high-energy electrons and independent of its local time, while external charging is related to low-energy electrons and dependent on its local time. As we noted in Choi et al. [2011], the flux of 100 keV electrons on GEO orbit shows nonuniform distribution on the local time, yet these electrons don't have enough energy to penetrate satellite walls and charge internal components. At this moment, we don't fully understand the mechanism by which charged particles bring about the anomalies. [4] We support the proposal made by Mazur and O'Brien [2012] that an agency be established to maintain adequate and open anomaly and abnormality lists containing all information about events. We also anticipate that our paper will serve as encouragement to all the agencies concerned to make their anomaly data publicly available and to investigate an occurrence mechanism of spacecraft anomaly. References

Space Weather Quarterly Volume 10, Issue 2, 2013

“…From Figure 3 we can conclude that a strong surface-charging environment is most likely between the local times of 22 and 06. Moreover, such environments are 50% more likely to occur during equinox seasons than solstice seasons, in agreement with the statistical anomaly findings of Choi et al [2011]. Finally, Figure 3 shows that strong surface charging appears to have a solar-cycle dependence, being least probable during solar minimum (2007) and most probable during the declining phase (2003).…”

“…The value hT e i=3300 eV is, by reference to Figure 6, the average electron temperature above which the spacecraft potential (whenever it could be identified by the ion line) is at least �100 V. From Figure 7 it is clear that strong surface charging conditions are limited to the premidnight-to-dusk region, with the vast majority of occurrences between~20 LT and 8 LT. This is exactly the range over which the majority of anomalies shown in Figure 3 of Choi et al [2011] occurred.…”

Parametric validations of analytical lifetime estimates for radiation belt electron diffusion by whistler waves

“…Quantifying the lifetimes of electrons trapped in Earth's radiation belts has become an increasingly important goal as scientists strive to predict high-energy particle fluxes, which may damage spaceborne high-technology systems (Iucci et al, 2005;Choi et al, 2011). However, observed flux variations related to the geomagnetic activity can reach orders of magnitudes over timescales of minutes to days (e.g., see Horne et al, 2005;Tu et al, 2010).…”

Reply to comment by Joseph E. Mazur and T. Paul O'Brien on “Analysis of GEO spacecraft anomalies: Space weather relationships”

“…Internal charging may be concerned with high-energy electrons and independent of its local time, while external charging is related to low-energy electrons and dependent on its local time. As we noted in Choi et al [2011], the flux of 100 keV electrons on GEO orbit shows nonuniform distribution on the local time, yet these electrons don't have enough energy to penetrate satellite walls and charge internal components. At this moment, we don't fully understand the mechanism by which charged particles bring about the anomalies.…”

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[1] The authors welcome the comment from J. E. Mazur and T. P. O'Brien [Mazur and O'Brien, 2012] on our recently published study [Choi et al, 2011]. In our paper, we investigated the geostationary Earth orbit (GEO) satellite anomalies archived by Satellite News Digest (SND) during 1997-2009 in order to search for possible influences of space weather on the anomaly occurrences.

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