Space Environment Effects on Space Systems...For information contact J. E. Mazur...

For information contact J. E. [email protected] 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

[email protected]

J. F. FennellThe Aerospace Corporation, M2/260, 2350 E. El Segundo Blvd., El Segundo, CA 90245

[email protected]

Presentation at theWorkshop on Science Associated With the Lunar Exploration Architecture

February 26-March 2, 2007Fiesta Inn ResortTempe, Arizona


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 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


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


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


Space Environment Hazards by Orbit

J. Mazur, Crosslink, vol. 4, no. 2, Summer 2003


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


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).


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

+ +


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


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?


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.


Single Event Effects (SEE)

(The Aerospace Corp.)


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


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.


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


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


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


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.


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


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.


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


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


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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