S11-4

Spacecraft Anomaly and Space Environment,
Space Weather and Satellite Alert system
衛星障害と宇宙環境 宇宙天気と衛星障害

Tateo Goka, Haruhisa Matsumoto, Kiyokazu Koga and Yugo Kimoto
五家建夫，松本晴久，古賀清一，木本雄吾
Japan Aerospace Exploration Agency (JAXA)
Sengen, Tsukuba-shi, Ibaraki, 305-8505, Japan
宇宙航空研究開発機構（JAXA）筑波宇宙センタ，〒305-8505 つくば市千現We assessed the effects of space environment on two Japanese spacecraft anomalies in JAXA during
an Oct. 2003 radiation storm. We revealed these anomalies were related spacecraft charging withenergetic electron, and developed satellite operation alert system using space weather technique.

1. Introduction
Space is filled with hot and low density plasmabuilding up high differential voltages resulting inelectrostatic discharges, sometimes causing
spacecraft anomaly. A recent spacecraft anomaly
statistic study [1] based on 326 environmentally
related anomaly records, concluding that spacecraft
charging has caused about 50 % portion in total
records, and the most serious ones (i.e., missionlost).
On Oct. 23, 2003, the first big large solar flare (X-raymagnitude class X5.4) was observed in the sunspot
region 486, where the subsequent ultra- large flareoccurred (X17 on Oct. 28, X10 on Oct. 29, and X28eon Nov. 04).
The NASA Goddard Space Flight Center Space
Science Mission Operation Team indicates thatapproximately 59 % of the Earth and Space Science
missions experienced effects from the October-November activity [2].

(1) Anomaly in the Earth Sensor and attitude control.
The Earth Sensor Assembly (ESA) experienced muchspike noises from 1530 (UT) on Oct. 28.
At 18:04 (UT) and before being anomaly flag reset byground command, ESA-A switched automatically toredundant ESA-B (retaining its anomaly flag). The
Attitude Control Equipment detected an anomaly, then,automatically entered safety mode (from three-axis
attitude control mode to slow- spin stabilized andsun-pointing mode) and Light Load Mode (LLM),
essentially shutting down all non-critical functions.
(2) The DRTS Recovery
After sequence of the extreme solar events, and after
mitigating the limit of fault detection level in Attitude
Control Equipment (ACE), three-axis attitude control ofDRTS was recovered on Nov. 7, at 12:19 (UT) byground command. DRTS is now operating normally.

2. DRTS (GEO) Anomaly(3) Relation between Anomaly and space environment
We found that the Earth sensor (exterior unit) produced
spike noise when 1MeV electron (also known asrelativistic electron) flux is high, before the solar extreme
solar events, on 24 March, 2003, 04:06 (JST). 25 March,
04:10 (JST), 3 April, 03:27 (JST), 28 May,
01:24(JST), and 6 June, 11:31 (JST). There was nothing out of
the ordinary in the ESA hardware. Those anomalies did
not affect satellite operation.

The Data Relay Test Satellite (DRTS), which has just thesame function as TDRS, was launched on Sept. 10, 2002,
and stayed in a geo-stationary orbit (GEO) at longitude
90.77 deg. east. DRTS entered safety mode, which ismeans sun-pointing slow- spin attitude control, andessentially shutting down all non-critical functions, onthe Oct. 28, at 18:42 (UT) just after the X-17 flare.

We made scatter plots for this time interval in 2003. The
results are presented in Fig. 1, where the vertical axis
represents 1MeV electron fluence integrated for one day(measured on DRTS) and the horizontal axis represents
spike noise counts per day. We marked ESA anomalies
with mesh circles.

We assessed the space environment effects of solar
activity during the Oct. 2003 radiation storm on twoJapanese spacecraft anomalies in JAXA.

(16:13 to 16:16 (UT)) on October 24 [7]. We willreport what occurred on the satellite, and related spaceenvironment effects.

DRTS E SAノ イ ズ と 電 子 Fluenc eの 関 係
107

10Alarm
Threshold→610 910 810 710ACE
Solar Wind5Electron Flux
ForecastProgram

10 610 5
Jan/21

Feb/2 Feb/13 Feb/25

Mar/8 Mar/20

Apr/1 Apr/12 Apr/24

Day

2-day forecast
104

110100E S A N o i s e C o u n t s [d a y - 1 ]Fig. 1: Correlation between DRTS/ESA spike noise andmeasured electron fluences, mesh circles indicate
anomalies.
ESA anomalies actually occurred when the 1MeV
electron flux or fluence was extremely high, and over thethreshold values, which is shown in the solid horizontal
line in Fig.1.
(4) High-Energy Electron Alert SystemA 1MeV range electron flux enhancement causes internal
charge (build-up of electrons charge inside the bulk of amaterial) and induces electrostatic discharge (ESD)
anomalies in satellites [3]. For safe satellite operation,
it is essential to predict the 1MeV electron flux level andalert satellite operators. An alert system for 1MeV
electron flux enhancement at geostationary orbit, whichis activated when predicted electron flux levels exceed acertain threshold, which is determined by ESA anomalies,
has been developed [4],We applied the linear prediction filter method [5,6] for electron flux forecasting method, using thesolar wind speed and electron flux correlation at
GEO, in Fig.2.
We calculated the cross-correlation between solar
wind (WIND: NSSDC) and 1MeV electron flux at
GEO (ETS-V) in 1995. The cross-correlation at +2
days after solar wind velocity increasing is thehighest
correlation
withelectronflux
enhancement. We then applied this +2 days
forecast relation to the high-energy electron （orESD ）alert System, shown in Fig.2 and SEES
home page (http://sees.tksc.jaxa.jp). This alert systembegan operating in 2003.
3. ADEOS-II (LEO-Polar) Anomaly
The Advanced Earth Observing Satellite II(ADEOS-II), also called Midori-II in Japanese, alow-altitude polar sun-synchronous satellite with analtitude of 800 km, suffered a catastrophic failure
during on October storm. Solar cell power output
dropped from 6 kW to 1 kW in three minutes fromDRTS
Electron Flux

SEES’s HP
２日後に、電子フラックスの増加が予測される。
DRTSの地球センサのFDIRが動作する可能性があります。
軌道制御等の運用は、避けて下さい。

ESD Alarm (E-Mail ) toSatellite Operation Center

Fig. 2: High-Energy Electron Alert System

It was probable that a short- or open- circuit failure
occurred on solar array paddle or solar array paddle
harness. For the latter, the laboratory test verified that thesustained arcing between harnesses could destroy thebundled power lines. Space environment analysis
demonstrated that the >30keV electron fluence (observedby NOAA-17) was two orders of magnitude greater thana quiet day on the just a quarter hours before theADEOS-2 power down outage anomaly at over the northpole aurorla region.
References[1] H. C. Koons, et al., The impact of the spaceenvironment on space systems, aerospace report,
No. TR-99(1670)-1(1999) p7-10.
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October 19 – November 07, 2003, ServiceAssessment, NOAA, (2004)[3] NASA, Avoiding Problems Caused by Spacecraft
On-orbit Internal Charging Effects, NASA-HDBK4002, Feb.17, (1999).
[4] K. Koga, H. Matsumoto, H. Koshiishi, K. Ueno, T.
Goka, Forecasting Relativistic Electron Variationsin the Outer Radiation Belt, 35th COSPAR
scientific Assembly (2004), COSPAR-04-A-03741
PSW1-0023-04,[5]T. Nagai, Space Weather Forecast: Prediction ofRelativistic Electron Intensity at SynchronousOrbit, Geophysics. Res. Let., Vol. 15, No. 5,p425-428, May (1988).
[6] D.N. Baker, et. al., Linear Prediction Filter analysisof relativistic electron properties at 6.6 Re, J.
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Takahashi, T. Goka, T. Kurosaki, M. Nakamura, K.
Toyoda, M. Cho, Investigation of Power System
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