BIRA-IASB, 30th October 2006

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1 Satellite Anomalies and Launch Failures: Space Weather Connection by Natalia Romanova Belgian Institute for Space Aeronomy Institute of the Physics of the Earth, Moscow, Russia BIRA-IASB, 30th October 2006 S1. Title Page The aim of this work is to perform a statistical analysis between the influence of the space weather on the functioning of satellites. Spacecrafts are exposed to various particles with different energies. And the intensity of these particles varies in time, duration and in location. In this report I present the main results concerning anomalies onboard geostationary and low-earth orbit satellites, as well as launch crashes. S2. Outline The outline of my talk is given here. I will begin my talk with an introduction to the background behind this work. Thereafter I present the databases used in this work, mainly the space environment databases and the satellite anomaly databases. The main part of this talk concerns studies performed using GEO spacecraft. I shall also show results about anomalies onboard LEO spacecraft, as well as accidents following spacecraft launches. At the end of my talk I will present the main conclusions of this work and their significance to world-wide space weather initiatives. S3. Typical faults in the on-board spacecraft equipment produced by the space environment On this slide the table presents the main technical problems that the space environment can have either on individual systems (e.g. components) onboard satellites or the satellites themselves. In the 3rd column the phenomena which are capable of causing these technical problems are listed. Generally there are many different types of spontaneous (not human-induced) anomalies, for example switching on/off of different equipment, change of orientation of antennas, a stopping delivery of the electric power from solar batteries, etc. It is necessary to take into account that failures of one type can be caused by different reasons. The green color highlights problems which result from the longterm impact of space weather, whereas the pink color signifies anomalies caused instantaneously by the space weather. At present, in the space industry, dielectric charging of space vehicles is considered the main negative factor, not allowing an artificial satellite to live out its expected lifespan. 1

2 S4. Animation It is necessary to distinguish the phenomena of the space environment capable of influencing satellites at different orbits. Applying the main concepts of solarterrestrial physics and the physics of the Earth s magnetosphere, a number of heliogeophysical phenomena which can influence satellites at different orbits in the near-earth space environment were used in this work. This slide shows schematically which phenomena a satellite may encounter in different parts of the near-earth space environment. For example, geostationary orbit spacecraft cross the external radiation belt where often the spontaneous increase of relativistic electrons fluxes occurs for reasons not yet fully understood. Part of the orbit of low-earth orbit satellites lies in the high-altitude area of Earth s magnetosphere where the intrusion of charged particles from the solar wind and from the night part of the magnetosphere during magnetic storms occurs most intensively. A satellite in such an orbit performs 14 passes a day. Solar protons with energy from 1 MeV and above can penetrate into the magnetosphere at any magnetic latitude. Galactic cosmic rays are protons and nuclei with energy exceeding 10 MeV/nucleon. It is also necessary to consider that the intensity of particle fluxes depends on the level of solar and geomagnetic activity. In our analysis we have used space environment data originating from the LANL and GOES satellite series, as well as the OMNI-2 database. S5. Anomaly Databases Used For this work five different anomaly databases were used: - US databases (NOAA and GSFC) - Former Soviet Union (Kosmos and High-Orbit Satellite) - Crashes after Launch (Pleseck) S6. Reasons of the anomalies onboard GEO-satellites in 22nd Solar cycle ( ) In the NOAA anomaly database a classification of anomilies was done as function of type. The distribution of anomalies with respect to their type (namely, UNK: Unknown, PF: Part Failure, ATT: Attitude Control Problem, PC: Phantom Command, HE: Hard Error; RSE: Recoverable, Soft Error, SS: System Shutdown; TE: Telemetry Error; and ESDM: Electrostatic Discharge Measured) is plotted in this figure. In the NOAA anomaly database the classification of various anomaly types was very incomplete and most of the anomaly types are unfortunately unknown. However, it was possible to link a large number of anomalies to SEUs as well as ESDMs. 2

3 S7. Solar proton events, magnetic storms and GEO satellites anomalies The October 1989 space weather event (DOY = ) is described in detail by Allan et al. (1989). Several solar flares produced strong geomagnetic storms (peak Dst = -280 nt) and bursts of solar proton events. Intense bursts of proton fluxes were detected by the IMP8 satellite (upper panel in the figure). At the same time the electron fluxes at GEO orbit also grew, but no evident bursts of intensity can be seen (middle panel). Moreover, the possibility of electron detector contamination by high proton fluxes should be taken into account. In the figure it is strongly seen that each solar proton event caused a sequence of satellite anomalies (vertical dashes in the upper panel). The anomalies occurred not only at GEO, but were also registered on satellites in other orbits. S8. Relativistic electrons and satellite anomalies From 1993 (the declining phase of solar maximum) the number of solar proton bursts began to decrease and this is clearly observed in the middle panel. However, the number of satellite anomalies did not decrease. During this period a series of moderate magnetic storms (Dst = -120 nt) occurred, probably associated with high speed solar wind streams. The example for the March-April 1994 storms ( day of year) shows that for this interval the flux rate of solar protons was low and very stable (middle panel). Instead the main menace for GEO satellites during this time period is magnetospheric relativistic electrons (known as "killer" electrons) they occur at the recovery phase of a storm when electron fluxes are rapidly enhanced, up to 2-3 orders of magnitude. It is seen here that each enhancement of relativistic electron fluxes produced a swarm of malfunctions onboard the geostationary satellites (vertical dashes in upper panel). The two events that have been presented here (the event on the previous slide and this event) show that under different phases of the solar cycle the dominating factors of the space environment differ and so does their individual impact on satellite systems. S9. Probability density (frequency functions) of the geostationary satellites anomalies on geomagnetic activity The figure shows that the probablility of a failure on a satellite increases with increase of geomagnetic activity. The analysis has been carried out separately for GEO Russian satellites and the NOAA satellites. In the left-hand panels the minimum observed around -220 nt (upper panel) and -250 nt (lower panel) is due to low statistics (there is no physical meaning). 3

4 Geomagnetic activity is characterized with geomagnetic indexes Kp and Dst that describe the level of geomagnetic disturbances in the Earth s magnetosphere. S10. Anomalies on geostationary satellites, particles fluxes and correlation between them during different phases of solar activity (22nd cycle) This figure shows the behaviour of the anomaly rate on geostationary satellites and particle fluxes during different phases of solar activity (22nd cycle) during 7 years. Panel 1 shows the GEO failure rate for NOAA data base Panel 2 the solar activity defined by sunspot number Panel 3 electron flux Panel 4 the correlation between anomaly rate and electron flux Panel 5 proton flux Panel 6 the correlation between anomaly rate and proton flux Special attention should be paid to the fact that the intensity of proton and electron fluxes depends on the phase of solar activity: During the growth and decline phases of solar activity an enhancement of relativistic electron fluxes occur. At solar maximum the highest correlation exists with protons. At the growth and decline phases the highest correlation is found with electrons. Note that there are two increases in electron flux, one in 1989 and one in They are probably due to proton contamination in the electron detectors. At solar maximum a combination of electrons and protons that cause the anomalies is suggested. Here we use intervals of 300 days for averaging. S11. Partial correlation coefficients between the frequency of GEO anomalies and space environment parameters during different phases of solar activity This table lists the independent correlations computed for the frequency of GEO anomalies and space environment parameters during different phases of solar activity. It was made with the use of factorial analysis. The first column represents the rising phase of solar activity, and it is seen that the sum of the factors of correlation between failure rate with electron and proton streams is equal to unit. This suggests that most anomalies during this phase of the solar cycle are caused by high-energy electrons and protons. During the decrease of solar activity the influence of electrons prevails. At solar maximum we see that the influence is combined (protons and electrons). 4

5 There is a period at solar maximum (July January 1991), when the correlation of the anomaly frequency with high-energy particles is zero. This period was investigated separately and on the next slide we present these results. S12. GEO satellite anomalies caused by ~100 kev electrons In the second half of 1990 the solar proton and magnetospheric relativistic electron fluxes were rather low, but satellite anomalies did not disappear. For satellite failures which occurred in the 2nd half of 1990, it is suggested that electrons with energy from 35 up to 100 kev are responsible for these anomalies. A few magnetic storms occurred during this period and on this figure we see that the time profiles of the anomaly frequency is similar to what is seen for the Kp index as well as for the electron flux. The high correlation with approximately 100 kev electrons points towards surface discharging of the satellites to be the reason of these failures. S13. Threshold particle flux for increased risk of GEO anomaly occurrence Electron and proton flux density threshold values, which represent a danger to spacecraft, are shown in this table. Values greater than these threshold values, represent the growth probability of satellite failure. For the electron flux this threshold value (column 4) is 2-3 times greater than the average value (column 5). For the proton flux this value is approximately 4 times greater than the average value. S14. Number of anomalies occuring onboard GEO satellites as a function of time of day - 1 It was found that the frequency of anomalies occurring at NOAA geostationary satellites depends on the time of the day. The slide shows the observed dependence of anomaly frequency on local time. The reason for the given anomalies is unknown. It can be seen that the probability of anomalies occurring increases during the morning and night hours. What could be the origin of such a tendency in this histogram? See next slide. S15. Number of anomalies occuring onboard GEO satellites as a function of time of day - 2 This second histogram shows the distribution of NOAA anomalies caused by electrostatic discharging as a function of the time of day. One can see that the obtained dependence for this type of anomaly is similar to that caused by unknown 5

6 reasons (compare with previous slide). As we know dielectric discharging/charging is caused mainly by high-energy electrons. Electrons drift from the night side of the magnetosphere to the morning side. Therefore one could suggest that most of the anomalies with undetermined origin, as determined by the flight control center, could be the result of high-energy electrons. S16. Estimation of the accumulative effect in the interaction of electron fluxes (above 2 MeV) with on-board satellite equipment It is seen that the correlation of anomaly rate with the integrated relativistic electron flux increases substantially. The electron flux is integrated over 2 days before an anomaly event occurs. This increase in correlation probably implies the occurrence of some kind of cumulative effect. That is, long-lasting high-energy electron fluxes are more dangerous to spacecraft than just the instant values. S17. Dependence of the correlation between the GEO anomaly probability and protons fluxes as function of their energy It is seen that with an increase in proton energy (0-10 MeV), the correlation with the failure frequency decreases quite fast. There is a small increase in this correlation above 30 MeV. This means that protons with energies 1-2 MeV are not less dangerous to satellites than the high-energy protons. S18. Low-Earth Orbit satellites: Annual anomaly probability and space weather parameters Now we go to the next part of our study which concerned low-earth orbit satellites. The slide shows some interesting results obtained for the possible relation between space weather factors and failures on low-earth orbit Russian satellites called Kosmos. It should be emphasized that all the Kosmos satellites (50 in all) are constructed in the same way. If the reason of an anomaly was human or technical it was not included in our study. Most of these satellite failures occurred during periods of enhanced solar activity (right-hand figure). The failure frequency varies on the season similar to the way geomagnetic activity does (left-hand figure). However our analysis shows that the failure frequency does not correlate significantly with the geomagnetic perturbations. Still some of the failures and satellite losses indeed happened during magnetic storms. 6

7 S19. Launch crashes at Plesezk cosmodrome (lat: 63, lon:41 ) Finally we show results obtained from our analysis on the origins of launch crashes at cosmodrome Plesetsk in Russia. The database has 1544 successful launches and 52 launch crashes covering the period from 1966 to We took into account only those failures that happened after the launch from the ground and excluded those that occurred on the ground during the start of the launch. This histogram shows that in summer time the crash frequency is two times larger compared to other seasons. The reason of this effect is still unknown. This cosmodrome is situated at high latitude in the auroral region where the manifestation of space weather is substantially stronger than at middle and low latitudes. S20. Launch crashes and geomagnetic activity This figure shows one of the cases when three failures occurred during a period of strong magnetic storms. The origin can be the impact of auroral electrons on the satellite equipment. The mechanism requires further investigation and is work in progress. S21. Conclusions S22 Thank you 7

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