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For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 1
Space Environment Effects on Space Systems
J. E. Mazur & P. O’Brien The Aerospace Corporation, CH3/210, 15049 Conference Center Drive, Chantilly, VA 20151
joseph.mazur@aero.org
J. F. FennellThe Aerospace Corporation, M2/260, 2350 E. El Segundo Blvd., El Segundo, CA 90245
joseph.fennell@aero.org
Presentation at theWorkshop on Science Associated With the Lunar Exploration Architecture
February 26-March 2, 2007Fiesta Inn ResortTempe, Arizona
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 2
We will review the space environment hazardsthat have been most important for spacesystems in Earth orbit and discuss some
implications for lunar exploration.
NASA-TM-2005-214062
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 3
For human and robotic productivity, we take theapproach that every mission will have roboticelements that must work irrespective of the
space environment and ask “What we can oneapply from near-Earth robotic experience”?
NASA-TM-2005-214062
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 4
Speaker’s Background & Interests
• Space science projects:• Co-I: SAMPEX, Ulysses, & LRO• PI: environmental sensor for TWINS-2• ACE: ULEIS instrument investigator• RBSP: instrument lead for relativistic proton spectrometer
• Current position: senior project leader at The Aerospace Corporation,Chantilly, VA
• Science interests:• solar particle acceleration & transport• trapped particles in the Earth’s magnetosphere• space environment interactions with space systems• next-generation radiation environment models
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 5
Surface degradation from radiation
Solar array arcdischarge
Electromagnetic pulse from vehicle discharge(on surface, behind thin shielding, or deep inside)
Single event effects in microelectronics
Spacecraft components become radioactive
False stars in star tracker CCDs
1101 ⇒ 0101
Major Space Environment Hazards
Solar array powerdecrease due toradiation damage
Before AfterBefore
During exposure tomulti-MeV protons
Electronics degrade dueto total radiation dose
Induced Voltage
Time
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 6
Space Environment Hazards by Orbit
J. Mazur, Crosslink, vol. 4, no. 2, Summer 2003
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 7
Survey to Determine the Impact of the SpaceEnvironment on Space Systems
Sponsored by the National Security Space Architect Aim was to quantify the impacts, especially cost Survey included all types of spacecraft for which we
were able to find data– Commercial, scientific, military– US domestic and others– >191 vehicles, 1970-1999
Main sources:– NOAA/NGDC– The Aerospace Corporation– NASA anomaly reports (Bedingfield et al. 1996;
Leach & Alexander 1997)– US Air Force 55th Space Weather Squadron
Known impacts: Service outages, missiondegradation, mission failure, data loss, sensordegradation, subsystem failure, launch delays,redesign & testing, anomaly analyses
Reference: Koons, H. C., J. E. Mazur, R. S. Selesnick,J. B. Blake, J. F. Fennell, J. L. Roeder, & P. C.Anderson, The Impact of the Space Environment onSpace Systems, Aerospace Corp. report no. TR-99(1670)-1, 20 July 1999
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 8
Impact Study Results
(The Aerospace Corp.)
ESD from charging was the dominant environment impact, and most of the eventsoccurred at GEO (where there is a large population of vehicles).
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 9
Spacecraft Surface Charging
• At equilibrium, the sum ofthe currents to the surfacemust be zero
• Satellite potential isdetermined by the energydistribution of the particlesproviding the current
• In the dark, the majorcontributor to the current isthe incident electrons
• In the dark, then, thepotential is closely relatedto the average energy of theelectrons
• Photo-currents generallydominate the sunlit regions
+ +
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 10
During substorms, a hot plasma is injected fromthe magnetotail into the nightside high-altitudeequatorial regions.
The electrons gradient- curvature drift towardsdawn and can dominate the charge balance on avehicle
The hazard arises when adjacent surfaces rise todifferent enough potentials to drive a discharge
A discharge can introduce unintended signals oftens of volts amplitude in command and powerlines
INSTRUMENT ANOMALIES
Surface Charging Hazard
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 11
Problem: Surface Charging Environment isHighly Localized
H. Koons, J. Mazur, A. Lopatin, D. Pitchford, A. Bogorad, & R. Herschitz, Spatial and Temporal Correlation ofSpacecraft Surface Charging in Geosynchronous Orbit, J. Spacecraft & Rockets 43, 178-185, 2006.
•These vehicles in GEO havesurface charging sensors tomeasure the potential of a samplematerial relative to the spacecraftframe.
•There is no correlation betweenthe potentials on adjacent vehiclesduring charging events in GEO,even as close as 4000 km.
•This means that surface potentialmeasurements are required on thespacecraft of interest and cannotbe inferred from nearby vehicles.
•Will ESD occur? Will the vehicleelectronics respond?
•What does the environment looklike at the moon with the addedcomplexity of the wake andboundaries?
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 12
Nominal Electron Flux
Another Problem: Little Difference Between Worst Case
and Nominal Electron Spectra
Roeder, J. L., Specification of the plasma environment at geosynchronous orbit in the energyrange 87 eV to 288 keV, TR-94(4940)-6, The Aerospace Corporation, 15 August 1994.
Subtle changes in the electron spectrum led to the worst-case chargingenvironment seen on SCATHA.
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 13
Single Event Effects (SEE)
(The Aerospace Corp.)
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 14
Single Event Transients Experienced in HEO
TID Effects of High-Z Material Spot Shields on FPGA Using MPTBData, S. H. CRAIN, J. E. MAZUR, and M. D. LOOPER,AEROSPACE REPORT NO. ATR-2003(7930)-2
Actel A1460A FPGAs
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 15
Single Event Effect (SEE) Cross Sections
The amount of energy lost bythe particle per unit pathlength in material is calledlinear energy transfer (LET)
Most devices have aminimum LET that is requiredto upset them, called thethreshold LET
Most device SEE crosssection does not increase forLETs greater than the kneevalue
Devices with low LETthreshold can be upset bylow mass high energy ionssuch as protons, helium,oxygen, etc.
SEE and TID Characterizatio of an Advanced Commercial 2Gbit NAND Flash Nonvolatile Memory, T. R.Oldham, R. L. Ladbury, M. Friendlich, H. S. Kim, M. D. Berg, T. L. Irwin, C. Seidleck, & K. A. LaBel, ,IEEETrans. Nuc. Sci. 53, 3217-3222, 2006.
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 16
Impact Example: Design of Attitude ControlSystems
E. Mikkelson & W. Baba, Solar flareproton environment for estimatingdowntime of spacecraft CCDs,IEEE Radiation Effects DataWorkshop, 14-17, 2002
Issue: downtime of CCDs due tobackground counts frompenetrating SEP protons
Concern: if start trackers will beoff-line due to protons, how willthe attitude control systemperform?
Analysis used October 1989environment as a specification
Not a real-time concern but aquestion for spacecraft design
Worst-case downtime would allowtrade studies of alternative controlsystems
The Solar and Heliospheric Observatory is a mission of international cooperationbetween NASA and the European Space Agency
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 17
Predicted Versus Observed Radiation Dose
The dose from the widely used environment model is woefullyinadequate, and this is in a relatively well-explored region of space
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 18
Begin to Address the Environment WithSpecifications
Specifications are thestarting point for systemdesign
These are cartoons of whatone might pass to thecontractors for a typicalorbiter design
For lunar missions, onewould also need surfacecharging and otherspecifications appropriate tothe missions and payloads
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 19
Specifications for Internal Charging -Including Lunar Phasing for MAP
These examples for internalcharging are based onenvironment measurements ofthe worst-case observations(not the worst-case inprinciple, which is unknown)
These spectra would be theinput for transport codes tocalculate the electron flux oninternal parts
The result is the shieldingrequired to reduce the fluencedown to a “safe” level basedon CRRES discharges
Different configurations andmaterials might suffer ESD atlower fluences
J. Fennell, H. Koons, M. Chen, & J. Blake, Internal Charging: A Preliminary Environmental Specification forSatellites, IEEE Trans. Plasma. Sci. 28, 2029-2036, 2000.
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 20
Mitigation of Environment Hazards
Mitigation is accomplished through design and test, not throughpredictions of environmental threats
Total dose and internal charging• Shielding where necessary
Vehicle charging/discharges• Make critical circuits insensitive to <100 µsec spikes• Carefully ground high impedance subsystems and protect inputs• Use shielded wiring, especially on exposed cables (1.5-2.0 mm Al)• Ground thermal blankets and use conductive or semi-conductive
materials on spacecraft surfaces• Test devices for susceptibility to discharges with MIL-STD 1541A
discharge testSingle event effects (partial list)
• Test parts to determine threshold LET and cross section• At parts level (if possible) maximize critical charge required for an
upset in the design• At circuit level, use onboard error detection and correction
techniques• At system level, add filters to suppress propagation of fast
transients
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 21
Environment Specifications for Lunar Missions Some specifications already exist for lunar missions
– LET spectrum from GCR (but see next talk by Jim Adams)– LET and dose from worst-case SEP events
Other specifications can be derived given our current knowledge ofthe environment and the mission profile, such as dose & internalcharging during transits of inner magnetosphere
Keep in mind that there continues to be uncertainty about some environments forthe well-inhabited orbits in the magnetosphere, and a new system always requires
consideration of how it will interact with the environment.
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 22
Environment Specifications for Lunar MissionsSurface charging & ESD will continue to be an issue for lunar missions
• Additional complexity of the dusty lunar body• Additional complexity of dust impacts and subsequent discharges?
Figure from CHARACTERIZING THE NEAR LUNAR PLASMAENVIRONMENT, T. J. Stubbs, this workshop.
Lunar systems must consider all the relevant space environment hazards, just asdesigners for new Earth-orbiting systems in new orbital regimes with new
materials, parts, and new requirements have to consider the comprehensive viewof where they are operating
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 23
Comment on Predictions of the SpaceEnvironment
Every lunar mission will require subsystems that operate with 100% duty cycleirrespective of the environment
– think of life support systems & electronics that control recovery from vehicle safehold– something has to keep a heartbeat, including the human payload
Safing is mentioned as a means of mitigating the effects of the spaceenvironment, but it can’t work for everything on the vehicle, so one comesback to the specifications
“With advance warning, engineers canpower down satellites and turn them awayfrom the sun, delay launches of craft andmake sure astronauts are not outspacewalking, and mitigate widespreaddamage to electronic systems on Earth.”The Sun’s Halo in 3-D, by Ron Cowen,Science News, vol. 170, August 19, 2006
“For now, scientists can only turn offsatellites and power grids to preventelectrical damage from the incomingparticles. They lose a little data orservice in the process but save thesatellite or grid in the long run.”
http://www.nasa.gov/centers/goddard/news/topstory/2003/0411tadpoles.html
For information contact J. E. MazurJoseph.mazur@aero.org703-324-8915 24
Summary
A new system always requires consideration of how it will interactwith the environment, including missions to the moon (crewed andnon-crewed)
Space environment specifications contain that information, are setearly in mission design, and are passed on to contractors just likethe launch environments
Lunar missions will need to consider single event effects from SEPand GCR, as well as vehicle charging
Charging of the lunar surface could be an issue in the magnetotailand in intense SEP events (Halekas et al. GRL 34, 2007)
It is not enough to know that an environmental threat is imminent;the system must survive
Predictions of upcoming environment events can be useful forsituational awareness, planning of uploads, and staffing on theground if necessary, but come too late for design work
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