SEARCH

SEARCH BY CITATION

Keywords:

  • space weather;
  • operations;
  • lessons learned;
  • best practices;
  • environmental effects

Abstract

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[1] The Sun-Earth space weather related to sunspots NOAA 484, 486, and 488 affected a number of NASA spacecraft and instruments between mid-October and early November 2003. Information available from Earth and space science missions indicate that about 59% of the spacecraft and about 18% of the instrument groups experienced some effect from the solar activity. This paper summarizes the impacts on spacecraft, instruments, and science data. The database that the paper is based on describes spacecraft and instrument effects observed as well as mission operators' preventive actions from 34 reporting missions. The database is Appendix A and provides additional material that could be of interest and that could be useful to satellite developers, operators, instrument managers, and scientists. The types of environmental effects observed were electronic upsets, housekeeping and science noise, proton degradation to solar arrays, upper atmosphere–induced changes to orbit dynamics, high levels of accumulated radiation, and proton heating. The paper develops best practices that are intended to foster continued and expanded feedback on the space environment in all mission phases, to promote designing to the mission's observing mode so that planning is appropriate to mission science goals, to distribute operational experience and lessons learned widely among both developing and operating missions, and to uniformly apply the developed knowledge base among NASA's missions.

1. Space Weather Environment

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[2] Beginning around 19 October and lasting until about 4 November 2003, the Earth's vicinity experienced an unusual increase in high-energy particle fluxes. The X-ray background flux sensed by the GOES spacecraft increased by about 2 orders of magnitude to 10−6 W/m2. The average proton flux also increased by about 2 orders of magnitude. Figure 1 shows sample flux for protons with energies greater than 10, 50, and 100 MeV. The increase in the number and intensity of X-ray flares, energetic particle flux peaks, and extreme ultraviolet (EUV) radiation events was a consequence of the coronal mass ejections (CMEs) and solar flares that occurred during this period and was a harbinger of stormy weather ahead. The X-ray and EUV radiation events were direct consequences of flares and within minutes of their origin caused changes in the Earth's atmospheric ionization, resulting in radio frequency propagation difficulties and in increases in ambient atmospheric density that affected the dynamics of some spacecraft in low Earth orbit. The CMEs' plasma interacting with the ambient solar wind spawned energetic particles, and the CME-driven shocks accelerated pre-existing particles to high energies. The magnitude of the resulting particle peaks caused a number of electrical effects on spacecraft.

image

Figure 1. Sample of proton flux from 26 October to 9 November 2003.

Download figure to PowerPoint

[3] The three giant sunspots were each larger than the planet Jupiter. The effects on Earth were many. Radio blackouts disrupted communications. Solar protons penetrated Earth's upper atmosphere, exposing astronauts and some air travelers to radiation doses equal to a medical chest X-ray. To get an idea of how the solar events in the fall of 2003 compare with other large solar events, consider that auroras from these events extended farther toward the equator than usual, appearing in Florida, Texas, Australia, and many other places where they are seldom seen. In California, where smoke from wildfires dimmed the Sun enough to look straight at it, the huge blotches on the Sun startled casual sky watchers.

[4] One of the spots, the one named NOAA 486, was the biggest in 13 years. These sunspots unleashed 11 X-class flares in only 14 days, equaling the total number observed during the previous 12 months. (Researchers rank solar flares according to their X-ray power output. C flares are the weakest. M flares are moderately strong. X flares are the most powerful. Each category has subdivisions: X1, X2, X3, and so on. X-ray flare classification uses a log scale. That is, an X-class flare is 10 times the strength of a correspondingly ranked M-class flare; for example, an X1 flare has 10 times the peak power of an M1 flare. A typical X flare registers X1 or X2. On 4 November, sunspot NOAA 486 unleashed an X28 flare, the most powerful ever recorded. In 1989 a flare about half that strong caused a widespread power blackout in Quebec. The recent blast was aimed away from Earth, so its effects on our planet were slight.)

2. Earth and Space Science Mission Impacts

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[5] The Sun-Earth space weather related to the sunspots affected a number of spacecraft and instruments. Information available from 34 NASA Earth and space science missions indicates that about 59% of the spacecraft and about 18% of the instrument groups experienced some effect from the solar activity. The impacts on spacecraft, instruments, and science are summarized in Tables 1a and 1b. In general, on-orbit missions implemented measures to detect the space weather events and took appropriate preventive actions. Some missions turned off their instruments or put them or the spacecraft in a safer operating mode.

Table 1a. Space Weather Effects Summary: Spacecraft and Instrument-Related Impacts
MissionChange in Operational StatusType of Space Weather Impacta
Electronic ErrorsNoisy Housekeeping DataSolar Array DegradationChanges to Orbit DynamicsHigh Levels of Accumulated RadiationProton Heating
  • a

    All of the impacts listed here, except the TRMM orbit changes and the RXTE errors uploading extended precision vectors, are due directly to solar energetic particles (SEPs) or similarly accelerated particles in geospace.

  • b

    ATS is absolute time sequence.

  • c

    EPV is extended precision vector.

  • d
Spacecraft Related
AquaNoneX     
ChandraInstrument safed    X 
CHIPSControl lossX     
ClusterNone  X   
GenesisAuto safedX     
GOES 9 and 10None X    
Ice, Cloud, and Land Elevation Satellite (ICESat)NoneX     
International Gamma-Ray Astrophysics Laboratory (INTEGRAL)Commanded safe      
Landsat 7Instrument safed      
MER A and BAuto safed X    
Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI)ATS stoppedbX     
RXTEEPVc load errors   X  
SOHOInstrument safed  X   
StardustAuto safedX     
Tracking and Data Relay Satellite System (TDRSS)NoneX     
TRMMAdded delta-V   X  
WindNone  X   
Number affected 74621
Number needing ground intervention 40021
 
Instrument Group Related
ACENone X    
GOES 8dInstrument lossX     
GALEXAuto safed and HV off X    
Mars OdysseyInstrument lossX     
NOAA 17Instrument loss      
RXTENoneX     
SIRTFNone     X
Number affected 321
Number needing ground intervention 310
Table 1b. Space Weather Effects Summary: Science Impacts
MissionChange in Operational StatusType of Science Impact
Loss of Instrument Functional CapabilityUnrecoverable Loss of Instrument DataReduced Quality of Recovered DataDelayed Availability of Data
Spacecraft Related
AquaNone    
ChandraInstrument safed X  
CHIPSControl loss X  
ClusterNone    
GenesisAuto safed X  
GOES 9 and 10None    
Ice, Cloud, and Land Elevation Satellite (ICESat)None    
International Gamma-Ray Astrophysics Laboratory (INTEGRAL)Commanded safe X  
Landsat 7Instrument safed X  
MER A and BAuto safed X  
Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI)ATS stoppeda X  
RXTEEPVb load errors   X
SOHOInstrument safed    
StardustAuto safed X  
Tracking and Data Relay Satellite System (TDRSS)None    
TRMMAdded delta-V    
WindNone    
 
Instrument Group Related
ACENone  X 
GOES 8cNoneX   
GALEXAuto safed and HV off  X 
Mars OdysseyInstrument lossX   
NOAA 17Instrument lossX   
RXTENone X  
SIRTFNone   X

[6] This paper focuses on benchmarking the mission effects for this period of atypical severe space weather and determining the science and spacecraft “costs” of such a severe event. The benchmark shows that even in one of the most severe space weather events of recent years the effects on and costs to the reporting spacecraft and missions were relatively modest. Also clear is that existing design practices and operations strategies did a pretty good job.

3. Spacecraft Impacts

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[7] Spacecraft impacts are depicted in the upper part of Table 1a. Five types of environmental spacecraft effects were observed [Barth, 2004]: electronic upsets, housekeeping noise, proton degradation to solar arrays, upper atmosphere–induced changes to orbit dynamics, and high levels of accumulated radiation. Seven spacecraft experienced electronic upsets, six had solar array degradation (Cluster, Solar Heliospheric Observatory (SOHO), and Wind), four had housekeeping noise (Geostationary Operational Environmental Satellite (GOES) 9 and 10 and Mars Exploration Rover (MER) A and B), one had high radiation (Chandra), and two had their orbits affected to the extent of needing an additional maneuver in the 2-week period (Tropical Rainfall Measuring Mission (TRMM)) or requiring workaround to generate precision vectors for upload (Rossi X-Ray Timing Explorer (RXTE)).

[8] Sometimes, though the effect was undesirable and serious, it was accommodated in the mission's design: The effect was a consequence that may be considered acceptable in terms of the mission's risk tolerance. For example, the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) flies a single-board computer (SBC) that is not very radiation hardened and so is built to recover autonomously, which it occasionally has to do because of the South Atlantic Anomaly. (The South Atlantic Anomaly is the region where Earth's inner van Allen radiation belt makes its closest approach to the planet's surface. For a given altitude the radiation intensity is higher over this region than elsewhere. It is produced by a “dip” in the Earth's magnetic field at that location, caused by the fact that the center of Earth's magnetic field is offset from its geographic center by 450 km. The South Atlantic Anomaly is of great significance to satellites and other spacecraft that orbit at several hundred kilometers altitude and at orbital inclinations between 35° and 60°; these orbits take satellites through the anomaly periodically, exposing them to several minutes of strong radiation each time. The International Space Station, orbiting with an inclination of 51.6°, required extra shielding to deal with this problem.)

[9] On 29 October the CHIPS SBC experienced a problem it could not recover from autonomously because it stopped executing. With the computer off-line the attitude control system was no longer able to maintain three-axis control, and CHIPS began tumbling. The flight operations team (FOT) responded to the anomaly by sending commands to reset the SBC, and the mission continued.

[10] None of the 34 NASA spacecraft this paper reports on experienced a permanent subsystem failure; all recovered autonomously or through ground intervention. However, Midori, a Japanese satellite, did fail during this period.

[11] Not all the effects observed had immediate mission consequences. Mechanisms like proton degradation to solar arrays, upper atmosphere–induced changes to orbit dynamics, and high levels of accumulated radiation have longer-term effects that limit the availability of electrical power and fuel needed to sustain the missions later in their lives and increase the probability of a shortened lifetime for system components. These effects are predicted, integrated into the design phase, and tracked during the operations phase to validate the prediction or to deal with the consequences of differences between prediction and observation.

[12] Solar array degradation information gathered so far indicates an accelerated loss of array power during the solar storm ranging from 0.65% to 1.4%. Missions affected include SOHO, Wind, and Cluster. Although it is interesting to note, each mission has enough of a margin so that this degradation is not a cause for concern. For the missions reporting, not enough data are available or too much time has passed to determine how much of the degradation is permanent.

[13] The severity of resulting operational changes is shown in the “change in spacecraft operational status” column in Tables 1a and 1b. Detailed impacts on Earth and space science mission spacecraft are listed in Appendix A.

4. Instrument Impacts

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[14] Instruments experienced three environmental effects: electronic upsets, science noise, and proton heating. Instrument impacts are depicted in the lower part of Table 1a. The relatively low percentage of missions reporting impacts reflects the success of instrument-related preventive actions. Many missions either turned instruments off or put them in a more benign operating mode. However, an Earth science mission (NOAA 17) and a space science mission (Mars Odyssey) did lose instruments, both on 28 October. The NOAA spacecraft is included here because NASA builds and delivers these spacecraft for the National Oceanic and Atmospheric Administration (NOAA). NOAA provides requirements, funding, and on-orbit operation.

[15] Two of the advanced microwave sounding unit's (AMSU) scan motors on NOAA 17 stopped on 28 October, both at approximately the same time (at about 0420 UT). As of 9 February 2004, electrostatic discharge, single-event upset, and X-ray flares were being investigated as potential failure mechanisms. Also on 28 October the Mars Radiation Environment Experiment (MARIE) instrument on Mars Odyssey had a temperature red alarm, leading it to be powered off. The MARIE instrument was lost permanently.

[16] Less severe impacts include the following: RXTE experienced high-voltage trips on two instruments. The Galaxy Evolution Explorer (GALEX) had noisy ultraviolet (UV) detector data, and the Advanced Composition Explorer (ACE) had saturated solar proton detectors. The Space Infrared Telescope Facility (SIRTF), now called the Spitzer Space Telescope (SST), had a 1.4°K telescope temperature increase attributed to proton heating.

[17] As stated in section 3, the severity of resulting changes is shown in the “change in operational status” column in Tables 1a and 1b. More details of impacts on Earth and space science mission instruments are also listed in Appendix A.

5. Science Impact

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[18] The effects on the availability and quality of Earth and space science data during the solar events were, in order of decreasing impact: loss of instrument functional capability (two missions; see section 4); unrecoverable loss of instrument data, caused by factors other than noisy data (nine missions); reduced quality of recovered data (two missions); and delayed accomplishment of planned events or delayed availability of data (two missions). Science impacts are depicted in Table 1b.

Table A1. Effects Observed and Preventive Actions
MissionSpacecraft ImpactInstrumentInstrument ImpactsPreventive Action
ACE   None
   Solar proton detectors saturated. Instrument will likely be recoverable when energy subsides. No other impacts. 
AquaNo spacecraft anomalies; observed increase in single bit (correctable errors) from a few per day to 80–400 per orbit; accelerated drag make up by 3 days  Increased monitoring during flares
  Aqua Humidity Sounder for Brazil (HSB)Instrument already off because of previous failureNone
  Aqua Atmospheric Infrared SounderInstrument returned to operations 6 Nov.Jet Propulsion Laboratory (JPL) requested instrument be turned off during storms.
  Aqua advanced microwave sounding unit (AMSU)Instrument returned to operations 4 Nov.JPL requested instrument be turned off 28 Oct. 2003.
  Aqua advanced microwave scanning radiometer for EOS (AMSR-E)Instrument returned to operations 5 Nov.Principal investigator (PI) requested AMSR-E be put into “modified sleep mode” 28 Oct. 2003.
  Aqua Clouds and Earth Radiant Energy System (CERES)Instrument performing nominal operations; no problems reported.PI preferred instrument continue to operate with elevated watch mode.
  Aqua Moderate Resolution Imaging Spectroradiometer (MODIS)Instrument performing nominal operations; no problems reported.Continued to operate in normal mode, with increased monitoring
Chandra (managed by the NASA Marshall Space Flight Center)The observing schedule was halted on 24 Oct. because of high radiation associated with solar flare activity. The loads were halted by ground command to execute a science instrument safing sequence, which ensured that the accumulated radiation dose for the advanced CCD imaging spectrometer (ACIS) remained below the allowed threshold. Loads will be restarted once radiation levels reach an acceptable level.  The observing schedule was halted on 24 Oct. because of high radiation associated with solar flare activity. The loads were halted by ground command to execute a science instrument safing sequence. This ensured that the accumulated radiation dose for ACIS remained below the allowed threshold.
CHIPSTook a hit but recovered via SpaceDev's proprietary fire code command. Was off-line for 27 hours because of X17 solar flare.   
ClusterSolar array degraded; net loss 1.4%   
ERBSNo problems reported. Concerned about command stored memory corruptions but did not experience any.  Increased monitoring
  Earth Radiation Budget Experiment Non-Scanner (ERBE-NS)Instrument performed nominal operations; no problems reported.Increased monitoring
  Stratospheric Aerosol and Gas ExperimentInstrument performed nominal operations; no problems reported.Increased monitoring
Galaxy Evolution Explorer (GALEX)  Excessive count rates received on the UV detectors but did not go to safe mode. Investigations continue into cause of single event upsets in the instrument.Have elected to turn off the high voltage to the detectors and to leave the system in the resulting nonobserving state until the current solar event is considered over
Genesis (managed by JPL)Entered safe mode because of software, processor flaw, or solar activity on 23 Oct., then re-entered safe mode upon reboot because of lockup in interface card. Second entry is designed to swap to side B of spacecraft. Decided 29 Oct. to return to side A so that we could know redundancy state of spacecraft. Performed B-side calculations while there in case swap to B occurs later. ETA for safe mode exit and return to science operations was 1 Nov. Spacecraft was hit with 19 memory errors on 29 Oct., which slightly delayed recovery to science operations.  Team waited for the solar activity to subside before attempting full recovery from safe mode. There was no need to rush, especially since the spacecraft continued to collect solar wind particles, its primary mission.
GOES 8, 9, 10, and 12High bit error rates (GOES 9 and 10)  Magnetic torquers disabled (GOES 9, 10, and 12)
  GOES 8 x-ray sensoraFailure under investigation as to cause 
Gravity Recovery and Climate Experiment (GRACE)Normal operations   
Ice, Cloud, and Land Elevation Satellite (ICESat)Normal operations; increase in GPS resets   
International Gamma-Ray Astrophysics Laboratory (INTEGRAL)Entered safe mode   
Landsat 7   Safed instrument for first day
Mars Global Surveyor (managed by JPL)No apparent effects from solar activity (normal operations). Older technology is more painful to operate but apparently more resilient to solar storms.  None needed
Mars Odyssey (managed by JPL)Experienced occasional star camera outages all day on 28 Oct., then entered safe mode on 29 Oct. because of memory error probably caused by solar activity. Rebooted on side A, which is where it remains. There is no evidence of side A damage. Odyssey has had at least one memory error  Project proceeded through the recovery procedure with ETA for safe mode exit and return to science operations early the week of 3 Nov.
  Mars Radiation Environment Experiment (MARIE) instrumentExperienced a major anomaly: power consumption increase and large temperature increase, followed by refusal to acknowledge commanding. It was turned off, and further troubleshooting activities are to be determined but after safe mode recovery. 
Mars Exploration Rover (MER) A and B (managed by JPL)Both entered “Sun idle” mode because of excessive star tracker events  The flight team continued to monitor the solar activity and decided on a recovery plan for use when the activities subsided. There was no limit on how long they could stay in this mode with no impact on mission activities
NOAA 17No problems reported   
  AMSU-A1On 27 Oct. 2003, lost scanner on AMSU-A1 instrument. Could not confirm whether related to space storm. Tiger team studying data. 
Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI)CPU reset three times between 25 and 28 Oct. Collateral pointing and flight software issues.   
   The CPU reset did not halt the instrument data processing unit, nor did the instruments halt collecting data. However, the absolute time sequence on board was lost, along with current time and several robotic telescope system sequences, which are not in programmable read-only memory (PROM). 
Rossi X-Ray Timing Explorer (RXTE)The course Sun sensor offset that was to be uploaded to electrically erasable programmable read-only memory (EEPROM) was postponed because of multiple X-class solar flares that may have upset commands to the spacecraft and memory writes. The uplink was rescheduled for Thursday morning, 6 Nov., pending space weather updates.  The uplink was rescheduled for Thursday morning, 6 Nov., pending space weather updates.
 The initial X17 flare caused multiple errors in the extended precision vector (EPV) load generation of 28 Oct. Vectors broke the 50 km limit for the first time in noted history of RXTE. With some manipulation, this EPV was successfully uplinked to the spacecraft without incident.  With some manipulation, this EPV was successfully uplinked to the spacecraft without incident.
  All-Sky Monitor (ASM)On 29 Oct. the RXTE spacecraft instruments encountered problems due to heightened solar activity. The first occurrence was an ASM scanning shadow camera 1 (SSC 1) latch up occurring at 1947. The ASM was recovered the next morning at 303/1507 UT. The ASM was inactive for 19.4 hours. The impact to data loss became known when the level 0 data was processed. Normally, these reactions can be seen when a solar storm causes the South Atlantic Anomaly (SAA) to expand. However, it was noted that the high-rate monitor (HRM) trip offs occurred while RXTE was not in proximity of the SAA.Notified Massachusetts Institute of Technology (MIT) about the situation with the ASM. MIT instructed us to leave the instrument off until the following morning. Subsequently, at 2122 UT, ASM SSC 2 and 3 experienced latch ups.
  Proportional counter array (PCA)During the same Tracking and Data Relay Satellite (TDRS) contact the science operations facility was alerted to HRM trip offs on PCU 3 and 4 occurring at 2058:44 UT. Because PCU 1 was left on the entire time, there was no data loss from the PCA.The PCA team was contacted and asked us to recover PCU 3 on a preliminary basis and watch the data for a reaction from solar activity. The PCU was recovered at 2304:26 UT. We observed that the PCU was no longer exhibiting high counts and recovered PCU 4 on the next pass at 303/0019:24 UT.
Space Infrared Telescope Facility (SIRTF)/Spitzer Space Telescope (SST)A slight heating of the telescope from 5.9°K to 7.3°K occurred during the solar activity, due to proton heating of the telescope, the net effect being equivalent to approximately 0.1 mW of added energy to the telescope. No degradation or noise has been identified in the star tracker assembly. All other observatory subsystems continue to function properly. Effect on the project has resulted in a slight delay of approximately 3 days in the completion of the science verification phase of the mission.  Project had in place a contingency plan wherein NOAA notifies the project when the proton flux units rise above 1 PFU (proton flux unit). SIRTF was notified of that condition on 25 Oct. Following that notification, the project initiated monitoring activities on a continuous basis to determine whether action would be needed should the critical 100 PFU level required for science instrument safety be reached. That level was reached on 28 Oct., whereupon SIRTF was positioned to Earth point, and the science instruments were turned off per the contingency plan.
SOHOSolar array degraded; net loss in 2-week period 1.1%   
  Ultraviolet coronagraph spectrometer (UVCS)NoneInstrument safed on 28 Oct. and returned to operations 30 Oct.
  Coronal diagnostic spectrometer (CDS)NoneInstrument safed on 28 Oct. and returned to operations 30 Oct.
Stardust (managed by the Jet Propulsion Laboratory)Entered safe mode because of interface card read errors probably caused by solar activity on 22 Oct. Project recovered from safe mode on 23 Oct. No discernable effects on performance. Cometary and Interstellar Dust Analyzer (CIDA) instrument not yet turned on but otherwise normal operations. Reperformed Sun-on-radiator slew 29 Oct. to decontaminate NavCam via heating. Stardust was located approximately on the other side of the Sun.  No specific actions
Tracking and Data Relay Satellite System (TDRSS)Some self-correcting memory errors  To be determined
TerraNo spacecraft anomalies; observed increase in motor drive assembly byte hits  Increased monitoring
  Terra Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER)Principal investigator requested to keep it operating.Instrument performed nominal operations; no problems reported.
  Terra MODISInstrument performed nominal operations; no problems reported.Continued to operate in normal mode with increased monitoring
  Terra Multiangle Imaging SpectroradiometerInstrument performed nominal operations; no problems reported.Increased monitoring
  Terra CERESInstrument performed nominal operations; no problems reported.PI preferred instrument continue to operate with elevated watch mode.
  Terra Measurements of Pollution in the Troposphere (MOPITT)Instrument performed nominal operations; no problems reported.Increased monitoring
Total Ozone Mapping Spectrometer (TOMS)No problems reported. Noticed increased noise on Earth sensorsIncreased monitoring
  TOMS instrumentInstrument performed nominal operations; no problems reported.Increased monitoring
TRMMFrequency of delta-V maneuvers increased from once every 14 days to 10 days.  Increased monitoring
  TRMM precipitation radarInstrument performed nominal operations; no problems reported.Increased monitoring
  TRMM microwave imager (TMI)Instrument performed nominal operations; no problems reported.Increased monitoring; no response from PI
  TRMM visible infrared scannerInstrument performed nominal operations; no problems reported.Increased monitoring; no response from PI
  TRMM lightning imaging sensor (LIS)Instrument returned to operations 4 Nov.PI requested to safe instrument.
UARSNo problems reported  Increased monitoring
  UARS SolsticeOn 
  UARS Solar Ultraviolet Spectral irradiance Monitor (SUSIM)On 
  UARS Halogen Occultation Experiment (HALOE) Turn on was delayed 1 day.
  UARS Active Cavity Radiometer Irradiance MonitorOff 
  UARS High Resolution Doppler ImagerOn 
  UARS Particle Environment Monitor (PEM) axisOn 
  UARS PEM Zenith Energetic Particle System (ZEPS)On 
  UARS PEM Nadir Energetic Particle Subsystem/High-Energy Particle SpectrometerOn 
  UARS Wind Imaging InterferometerOff 
WindSolar array degraded; net loss in 2-week period 0.65%   

[19] While turning instruments off or putting them into a more benign operating mode may have contributed to mitigating instrument problems and is a good preventive action, it results in science loss. About 26% of the missions had this experience either as a commanded preventive action or an autonomous spacecraft action.

[20] All nine missions that altered instrument operation had data delayed. Since this was planned, it does not contribute to the “delayed availability of data” category in Table 1b. However, delays related to Sun-Earth weather can be significant in instances when the disruption happens around a special, one-of-a-kind operation or impacts an important schedule milestone that could involve money or other resources. In this instance, RXTE delayed for about a week a flight software change required to prevent potential damage to its solar array that occurs after a safe mode event, and SST (SIRTF) had a slight delay of approximately 3 days in the completion of the science verification phase of its mission.

[21] Two instruments experienced reduced quality of recovered data. Solar proton detectors saturated on ACE. UV detectors had excessive count rates on GALEX.

6. Mission Preventive Actions

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[22] Preventive actions initiated by the missions reporting, in order of increasing mission impact, were: exercised existing contingency plans that used information from the NOAA Space Environment Center (SEC) or from available relevant mission data, increased monitoring of solar activity and spacecraft systems in response to worsening space weather, worked around detrimental orbit dynamics effects, turned off instrument high voltages, safed instruments, and safed spacecraft and delayed recovery until the severe environment subsided.

7. Lessons Learned, Operations Recommendations, and Options

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[23] In general, missions factored the possible effects of severe space weather into their design as much as practical. Typically, on-orbit missions have in place the measures to detect space weather events and to take preventative measures.

[24] Even though mission performance was good, there still were significant undesirable effects. Appendix B provides a set of recommendations as “best practices” intended to shift the performance curve more to the desirable end, making “good” performance “better.” The crosscutting recommendations apply to all missions, and the options are recommendations that should be considered and implemented only if circumstances warrant. Developing these recommendations was a challenge for at least two reasons: From a design perspective, missions are faced with mitigating risks when the causes are associated with processes that are not well understood and are imbedded in a rare, complex series of events such as those of October–November 2003. Thus, depending on when a mission flies, technology may not have effective solutions to offer. In addition, from both a design and an operations perspective, improving already good performance in times of highly constrained budgets runs the risk of using more resources than may make sense. Therefore the challenge was also to develop recommendations to improve performance while using judgment to develop a cost-effective implementation based on the consequences to mission requirements.

[25] The results attempt to better performance by developing recommendations in the context of these challenges that espouse using a combination of technology and operational techniques appropriate to the mission. The way these techniques are combined depends on the value of the particular mission's science; the susceptibility of spacecraft or instruments to space weather as defined by analyses or operational experience; the readiness level of needed technologies; and the impact to the mission's science, spacecraft, and instruments' welfare associated with operational workarounds. The earlier example of CHIPS illustrates such a technology-operations strategy combination. Other examples are Chandra, ACE, and Wind. Chandra's requirements allow halting its observing schedule and safing its science instrument to ensure that the accumulated radiation dose remains below the allowed threshold. Thus, for Chandra, such storms are merely nuisances. On the other hand, ACE and Wind, which study the very phenomena of space storms, certainly cannot have their instruments or spacecraft safed and must be designed and operated in recognition of this fact.

[26] Shifting the performance curve to the more desirable end includes the following recommendations: (1) Continue and expand feedback on the space environment among operations teams, science managers, and designers. (2) When the mission warrants it, design to the mission's observing mode. Give consideration to an instrument and mission design that permits riding out solar storms in an observing mode. (3) Distribute operational experience gained widely and manage missions uniformly. The important concepts to imbed in mission planning and operations are to know mission susceptibility to storms in the Sun-Earth environment before operations start, to assess mission risks and develop a contingency plan before operations start, and, as sanctioned by mission needs, to set susceptibility metric levels (particle flux levels, X-ray class, etc.) at which instruments or spacecraft are safed.

Appendix B:: Operations Recommendations and Options

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information

[28] In general, NASA Earth and space science missions have factored the possible effects of severe space weather into their design as much as practical. Typically, on-orbit missions have in place the measures to detect space weather events and to take preventative measures when appropriate. The following recommendations are given as best practices. The crosscutting recommendations apply to all missions, and the options are recommendations that should be considered and implemented only if the circumstances warrant.

B1. Crosscutting Recommendations
B1.1. Recommendation 1

[29] The first recommendation [Barth, 2004] is to know mission susceptibility before operations start. The mission developer and flight operations team (FOT) need to document mission susceptibility to storms in the Sun-Earth environment before the operations phase begins.

[30] Knowing and dealing with mission susceptibility needs to be backed up even further into the design phase to include adequate modeling and mitigation of energetic charged particle hits, for example, in designing the radiation shielding for the charge-coupled device (CCD) detectors for the Solar Dynamics Observatory mission instruments. This necessitates maintaining a close relationship with radiation effects and analysis efforts in order to continue strengthening the ability to determine susceptibility.

[31] To estimate susceptibility, look for design analyses that describe the expected performance of the spacecraft and instrument's subsystems. Also, use FOT experience: the information gained during previous disturbances from the past performance history of similar Earth and space missions.

B1.2. Recommendation 2

[32] The second recommendation is to assess mission risks on the basis of mission susceptibility to space weather and to develop a contingency plan before operations start. The space weather contingency plan defines preventive actions the FOT is authorized to do and is directed at mitigating risks associated with mission susceptibility. In addition to operations input, the space weather contingency needs inputs from several other organizations and the science community to ensure that the plan reflects both the most recent engineering knowledge and current science objectives. The plan should take into account the value of space weather to the mission's science goals and objectives. That is, the options available for preventive action must be consistent with the mission's science. If the mission has instruments designed to collect data produced by the disturbed environment, such as looking at the Sun, spacecraft preventive actions may be limited so that some instrument operations continue.

B1.3. Recommendation 3

[33] The third recommendation is to find out if a space weather event is happening. It is vital to know how we find out if another event of this sort is happening and what we should do when we know.

[34] Some Earth and space science spacecraft payloads serve as the source of the data needed to find out if a space weather event is happening. Some of this payload data may be used to monitor the environment's effect on the spacecraft's instruments and may be included in housekeeping data.

[35] The likeliest source of useful data in a reasonable time frame is the NOAA Space Environment Center (SEC). The SEC provides real-time monitoring of solar and geophysical events and forecasting for solar and geophysical disturbances. The SEC provides a wide variety of near-real-time and recent space weather data online through its Web and ftp sites. Data on the space weather environment are described as solar, interplanetary, geomagnetic, and near-Earth and are provided from sensors on the ACE, Polar Operational Environmental Satellite (POES), GOES, and Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) (see Figure B1). Space weather alerts are available via e-mail, fax, pager, and National Weather Service systems.

image

Figure B1. Online capabilities of the Space Environment Center (SEC).

Download figure to PowerPoint

B1.4. Recommendation 4

[36] Recommendation 4 is to increase spacecraft and instrument monitoring for health and safety during space weather alerts.

B1.5. Recommendation 5

[37] Recommendation 5 is to set susceptibility metric levels at which instruments will be turned off or safed. These metrics need to be defined in terms of sensible and available space environment parameters such as particle flux levels or X-ray class.

B1.6. Recommendation 6

[38] Recommendation 6 is to set susceptibility metric levels at which the spacecraft will be safed.

B1.7. Recommendation 7

[39] Recommendation 7 is to include science team and spacecraft-sustaining engineering points of contact in the alert mechanisms defined in the mission's space weather contingency plan.

B2. Mission Unique Recommendations/Options

[40] Preventive actions that are mission unique depend on the particular mission's spacecraft and instrument's susceptibility to the Sun-Earth environment. The FOT should develop procedures to deal with space weather risks. The procedures should detail as much as practical immediate preventive actions to be taken by the mission director and FOT and should be based on monitoring the mission's established susceptibility metrics using the NOAA Space Environment Center or, if the situation warrants, the predefined mission data available to the FOT. Depending on the mission and impact of risk, options for preventive action consist of the following recommendations.

B2.1. Recommendation 8

[41] Recommendation 8 is to implement automated environmental monitoring in order to increase operations reliability and simplicity.

B2.2. Recommendation 9

[42] Recommendation 9 is to increase both spacecraft and space weather monitoring in stages so that the increasing impact of weather changes can be accommodated more reasonably. With a good contingency plan this potentially provides a good return for a minimal effort.

B2.3. Recommendation 10

[43] Recommendation 10 is to turn off instrument high voltages. This may be easy to do and will eliminate a source of stress caused by a high particle flux environment.

B2.4. Recommendation 11

[44] Recommendation 11 is to turn instruments completely off. Science is not available from the instrument, but this may be the best way to lower some risk while still collecting some valuable science from other instruments.

B2.5. Recommendation 12

[45] Recommendation 12 is to put the spacecraft in safe mode. Science is not available, but safe mode is sometimes the best way to lower the risk of instrument or mission loss.

B2.6. Recommendation 13

[46] Recommendation 13 is to reorient the spacecraft or to modify the orbit to shield vulnerable components from the environment or to avoid regions of severe weather. These may be major operational impacts but may be needed in conjunction with safing the spacecraft and instruments if the environment is very severe or the mission is extremely valuable and warrants the added cost of eliminating uncertainty. Implementation needs to be integrated in the space weather contingency plan and may require significant mission planning and flight dynamics monitoring and lead time.

References

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information
  • Barth, J. L. (2004), Space weather influences on mission operations, paper presented at Goddard Space Flight Center Earth Observing System Seminar, NASA Goddard Space Flight Center, Greenbelt, Md., February.
  • Webb, D. F., and J. H. Allen (2004), Spacecraft and ground anomalies related to the October–November 2003 solar activity, Space Weather, 2, S03008, doi:10.1029/2004SW000075.

Supporting Information

  1. Top of page
  2. Abstract
  3. 1. Space Weather Environment
  4. 2. Earth and Space Science Mission Impacts
  5. 3. Spacecraft Impacts
  6. 4. Instrument Impacts
  7. 5. Science Impact
  8. 6. Mission Preventive Actions
  9. 7. Lessons Learned, Operations Recommendations, and Options
  10. Appendix A:: Spacecraft and Instrument Environmental Effects
  11. Appendix B:: Operations Recommendations and Options
  12. Acknowledgments
  13. References
  14. Supporting Information
FilenameFormatSizeDescription
swe41-sup-0001-tab01a.txtplain text document2KTab-delimited Table 1a.
swe41-sup-0002-tab01b.txtplain text document1KTab-delimited Table 1b.
swe41-sup-0003-taba1.txtplain text document13KTab-delimited Table A1.

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.