E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 2004 Effects on Space...

E. Valtonen, Space Research Lab.April 5, 2004

Seminar in Space PhysicsSpring 2004

Effects on Space Technology

Space weather

Michael J. Golightly

NASA Johnson Space Center



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Overview of space weather effects

Lanzerotti, 2001

ESTEC, Space Environmentsand Effects Analysis Section



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• Ground effects

• Effects on oil drilling

• Effects on train light signals (two documented events in Sweden)



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• Effects on communication, navigation and positioning

• Signal “scintillation” Loss of signal lock on satellites Both single and dual frequency systems may

be affected

• The Total Electron Content (TEC) along the path of a GPS signal can introduce a positioning error ( up to 100 m)

A 7-10 km height change of the lower ionosphere can give position errors of 1-12 km



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• Global effects



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Impacts on animals

• The navigational abilities of homing pigeons are affected by geomagnetic storms

• Pigeons and other migratory animals, such as dolphins and whales, have internal biological compasses composed of the mineral magnetite wrapped in bundles of nerve cells.




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• Atmospheric drag of satellites

Increased satellite drag and loss of orbit tracking magnifies the risk of collisions with orbiting debris

In addition to loose altitude satellites can also start tumblingsince the satellites in most cases are non-symmetrical• Hubble Space Telescope drops 10-15 km per year• Skylab re-entered several years earlier than planned

• Tumbling - Low Earth Orbit (LEO) magnetic linkage between satellite and momentum transfer wheel affected by field-aligned currents during substorms & other dynamic events.



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• Effects on man in space



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• Effects on technologies in space

Surface charging Internal charging Total ionising dose Displacement damage Single event effects Interference and background in instruments

Source Drain

Floating Gate ONOTunnel Oxide

Control Gate

VCC

Data Path

Ionizing Radiation



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Plasma effects

• Surface charging

• Plasma effects on instruments



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Surface charging

• Absolute charging: build up of high potentials on spacecraft relative to the ambient plasma fast process (microseconds) not in itself necessarily a serious concern enhances surface contamination degrading thermal properties compromises scientific missions seeking to measure properties of space

environment

• Differential charging: build up of potential differences between various parts of a spacecraft relatively slow process (minutes) because of capacitance non-uniform material properties shaded or sunlit anisotropic plasma fluxes

• Effects by discharge arcing



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Surface charging

Object placed in a plasma will charge negatively due to the greater mobility of electrons compared to ions

Current equilibrium condition: at potential V

Negative surface charge prevents eV-electrons to reach the surface Equilibrium reached when the sheath region sufficient to balance currents

due to positive and negative plasma species Spacecraft will assume a floating

potential different from the plasma Assuming a single Maxwellian

distribution for the plasma gives

V -Te in eclipse (and Te> 1 keV)

plasma

}

photoelecronssecondary electrons

backscatteredelectrons

artificial source

Ie+Ii+Ipe+Isec+Iback+Iart=0



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Surface charging At low energies (tens of eV) the secondary emission ratio exceeds unity Typically at 1-2 keV, emission ratio drops below unity charging Hot plasma (20 keV) injected from the magnetospheric tail during

substorms

Gubby and Evans, JASTP 64, 1723 (2002)

Anomalies concentrate in themidnight-morning sector.



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Surface charging

In sunlight photocurrent from a surface much higher than plasma currents: equilibrium controlled by emission and reattraction of photoelectrons by UV flux

In conditions with no sunlight and low cold plasma density (outside of the plasmasphere) surfaces can charge to very high potentials

Upon exiting eclipse various surfacematerials discharge at different rates possibility of large differential potentials

Wake effect in LEO: spacecraft velocity> ion velocity, but < electron velocity ions impact only ram surfaces, electronsall surfaces differential charging

worsens the otherwise favourable environment of high-density low-energy plasma



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Surface charging• Modeling discharge characteristics

Spacecraft in space considered as a capacitor relative to the space plasma potential Dielectroc surfaces divide the spacecraft into many capacitors The components of the system of capacitors are charged at different rates

dependent on incident fluxes, time constants, spacecraft configuration effects etc. Sophisticated computer programs needed taking into account 3-dimensional effects

NASA Charging Analyzer Program (NASCAP)

• Mitigation in design Basic geometry and grounding of surfaces Conductive surfaces Knowledge and selection of

dielectric thickness dielectric constant ( surface capacitance) dielectric resistivity (generally not a constant in space environment) surface resistivity secondary emission yields photoelectron yield



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Surface charging• Surface charging effects

Charging leads to arc-discharge process releasing large amounts of charge currents flowing in structures broad-band electromagnetic field coupling into electronics

Undesired effects due to discharge arcing currents and EMI generation dielectric breakdown (punch-through) between surfaces (flash-over)

noise in data and wiring telemetry glitches logic upsets spurious commands materials damage (sputtering, change of conductivity, darkening) attraction of chemically active materials

Examples Marecs-A, 1981, GEO, 617 anomalies in status monitoring circuits Anik E1 and E2, 1991, GEO, a large number of mode switches

Koons et al., Aerospace Report No TR-99(1670)-1:The most serious spacecraft anomalies have been caused by surface charging, including 4 out of 11 missions lost or terminated due to space weather effects



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Plasma effects on instruments

• Discharges in high-voltage circuits• High potentials in plasma instruments

Distorts energy distribution of incident ions instrument bias with respect to plasma ground

Perturbation of particle trajectories angular resolution sensitivity

High ground potentials

• Sputtering of surfaces due to considerable ion kinetic energy X-ray mirrors Contamination source

re-attraction of ionised outgassing and sputtering products Change of thermo-optical properties of thermal control surfaces

• Dust generation and shedding Startracker anomalies Infrared sensor interference



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Radiation effects

• Internal charging

• Total ionizing dose

• Displacement damage

• Single event effects

• Sensor background and interference



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Internal charging

Range in AluminiumElectrons: ESTAR

Protons: SRIM-2003

0,0001

0,001

0,01

0,1

1

10

100

1000

10000

0,01 0,1 1 10 100 1000Energy (MeV)

Ran

ge

(mm

)

ESTAR

Weber Max

SRIM-2003

Surface charging0 - 50 keV electrons

Internal chargingE > 0.1 MeV electrons

Penetration of electrons and protons through material:Electrons > a few 100 keV capable to penetrate through shielding internal charging (deep dielectric or bulk or thick charging)



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Internal charging

• Basic cause of internal charging: electrons accelerated in the magnetosphere during extended intervals of enhanced geomagntic activity

• Moderate geomagnetic storms temporarily depopulate energetic (> 50 keV) electrons at GEO wave-particle instability gross changes in the morphology of the magnetic field

precipitation

• Refilled within 1-2 days by diffusion of electrons accelerated deeper in the magnetosphere producing greatly enhanced fluxes and harder spectrum at GEO



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Internal charging

• Time-integrated flux (=fluence) important Charge builds up when charge leakage rate < charge collection rate Discharge occurs when electric field > 2x105 V/cm >2 MeV electron flux >3x108 cm-2sr-1d-1 for 3 consequtive days or

>109 cm-2sr-1d-1 for a single day

• Electrons >100 keV penetrate into and are

trapped in isolated parts Highly insulating dielectrics Floating conductors

• Electrostatic discharge via Groundlines Structure

High-energy electrons

ZAP!

Wrenn and Sims, AGU Monograph no 97, 275 (1996)



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Internal charging• Local time distribution of internal charging anomalies different

from surface charging anomalies reflecting More uniform distribution of relativistic electrons Cumulative effect

• Capacitor plate equation

typermittividielectric

tyconductividielectric

timerelaxation

tJ

d

tVtE

/exp1)(

)(

J/ > dielectric strength discharge

High-density of (lower-energy) electrons (LEO) large JHigh-energy (lower-density) electrons (GEO) high V } High E



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Internal charging• Potential targets for internal charging

Dielectrics cable wrap wire insulation PCBs feed-throughs

Floating conductors PCB metallization islands

CRRES results established the importanceof internal charging as a source of anomalies

Violet & Frederickson, IEEE Trans. Nucl. Sci. 40, 1512 (1993)



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Internal charging

• Internal charging effects Discharge producing spurious signals

Electromagnetic transients coupling into electronics systems control signals in coaxial cables

• unintended logic changes• command errors• phantom commands• spurious signals

loss of synchronization degraded sensor performance damage to sensitive components connected to discharging cable

Physical damage Localised heating Breakdown of thermal coatings Ejection of surface material

Difficult to distinguish from surface charging initiated discharges Environmental parameters important (correlation with high-energy electron fluxes)



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Internal charging Examples

DRA , 199?, GEO, 120 identical status switching anomalies The classic local time pattern only exists during active periods At quieter times anomalies are evenly distributed in LT

Meteosat-3, 1988, GEO, 725 operational anomalies Many anomalies linked to ”injection events” (3-9 hours LT) Others occurred during average or low instantaneous fluxes (at all LT) Both types interpreted as internal charging anomalies

Local time distributions of DRA (left) and Meteosat-3 anomalies attributed to internal charging

high-flux (shaded)low-flux (striped)

Wrenn, G.L., JSR 32, 514 (1995) Rodgers, D.J. et al., ESA WP-155 (1999)



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Internal charging• Internal charging depends on

environment shielding thickness characteristics of the charged material shape of the charged material

• Modeling object geometry environmental model (electron flux) charge deposition from an energy-range curve electric field calculation assuming temperature dependent conductivity breakdown threshold (requires test)

DERA Internal Charging Threat Assesment Tool (DICTAT)

• Mitigation proper grounding shielding leaky dielectrics EMI susceptibility reduction techniques orbit selection



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• Measured in terms of absorbed dose• Energy deposited in ionization and excitation per unit mass

Ionization energy loss:

Absorbed energy goes mainly into production of electron-hole pairs Electrons highly mobile Holes less mobile some portion trapped

TID comes mostly from (low-energy) protons (high intensities, highly ionizing) Trapped protons Solar (flares and CMEs) protons

Also from Trapped electrons Bremsstrahlung

Long-term failure mechanism Cumulative effect Described in terms of Mean Time To Failure (MTTF)

Total ionizing dose

2

2

mv

Znz

dx

dE

i

7.6x1012 e-h pairs/rad(SiO2)cm3



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Total ionizing dose

Dose rate important Directional fluxes Depends on mission

orbit altitude and orientation duration and timing relative to the solar cycle

Basics of dose calculation:

Mission specificationRadiation environment model} compute charged-particle fluxes f(E)

Radiation transport results D(E,d)Define simple shielding geometry

calculate dose-depth curve D(d)=ΣE f(E)·D(E,d) E}

Define actual geometry and shielding materials Dose at a point

E.g., Shieldose



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Total ionizing dose

Spenvis/Shieldose-2 calculation of annual dose

Dose at various orbits (AE8/AP8+JPL-91)

1,0E+01

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E+06

1,0E+07

1,0E+08

1,0E+09

0,0 5,0 10,0 15,0 20,0Al shield thickness (mm)

Do

se [

Rad

(si)

]

Polar

GEO

GTO

Examples of total dose-depth curves in various orbits

Annual dose behind 4 mm spherical shieldingon circular equatorial orbits (ECSS-E-10-04A).



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Total ionizing dose

• Total ionising dose effects Caused by trapping of charge in insulators

bulk (SiO2)

recombination centres field effects

interfaces (Si-SiO2)

direct effects on the bulk Si

Static and dynamic response altered threshold voltage shifts charge carrier mobility degradation increased leakage current gain degradation change in frequency response increased power consumption

Leakage channel



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Total ionizing dose

• Other types of total dose effects Glass coloration Polymer bond breaking Luminescence

• Avoiding total dose effects Component selection Component design Control of manufacturing process Shielding Cold redundancy

• Total ionizing dose effects becoming increasingly important



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Displacement damage• Measured in terms of Non Ionizing Energy Loss (NIEL)

Small part of energy loss in a medium goes into non-ionizing processes Elastic scattering Inelastic scattering Other inelastic processes

Corresponds to the ”nuclear stopping power” in the total dE/dx Kinetic energy ternsferred to the atoms of a medium

Contributing particles protons electrons > 150 keV (secondary) neutrons

NIEL function N(E) or its normalized form

N10(E) to derive the non-ionizing dose or the10 MeV equivalent proton damage fluence

• Displacement damage is a cumulative, long-term mechanism

ECSS-E-10-04A

E E

DN EENEfForEENEfD )()()()( 10



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Displacement damage

• Lattice displacement damage due to non-ionizing energy loss Primary knock-on atom (PKA) Vacancy

Interstitial + vacancy = Frenkel pair

Energetic PKA clusters highly disordered region in the lattice

• Displacement damage mechanism Frenkel pairs extremely mobile

Recombination Those that are not recombined form stable complex defects in the lattice

divacancies Si E centres (with P impurities) Si A centres (with O impurities)



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Displacement damage

Defects give rise to states with energy levels in the Si forbidden bandgap which can lead to

Generation of e-h pairs Recombination of e-h pairs Trapping of charge carriers Compensation of donors or acceptors Tunneling of charge carriers

I.e., Change in equilibrium carrier concentration Change in minority carrier lifetime

Displacement damage effects Reduction of gain and increase of leakage current in bipolar devices Reduced efficiency of solar cells, light emitting diodes and photodetectors Degraded charge trasfer efficiency in CCDs Resolution degradation in solid state detectors

increase of leakage current change in depletion voltage

Altered optical properties

The volume leakage current increase due to defects:I/V=qni/g,g=generation lifetime



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Displacement damageAn example: SOHO solar array degradation and SOHO/ERNE Si detector leakage current

SOHO/LASCO andSOHO/EIT images

SOHO/ERNE HED Bias 3 Jan 96-Feb 02



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Displacement damage

• Joe H. Allen, SCOSTEP

• 2000/10/23



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Single event effects

• Radiation induced observable effect in microelectronics circuits caused by a single charged particle losing energy by ionization in a small sensitive target Ionizing particle produces a conductive path through a circuit Current pulse or a continuous current path created

• Instantaneous mechanism• Expressed in terms of propability

• Many types of single event effects (SEE) SEU, SET, MBU, SEL, SEB , SEGR, SEDF, SEFI, SHE, ...

• Characterised by Linear Energy Transfer (LET)

Pickel, 1983



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Acronym Definition DescriptionSEU Single Event Upset Change of information storedSED Single Event Disturb Momentary disturb of information

stored in memory bitSET Single Event Transient Current transient induced by

passage of a particle, canpropagate to cause output error incombinational logic

SEDR Single Event DielectricRupture

Essentially antifuse rupture

SEGR Single Event Gate Rupture Rupture of gate dielectric causedby a high current flow

SEL Single Event Latchup High current regenerative stateinduced in 4-layer device (latchup)

SES Single Event Snapback High current regenerative stateinduced in NMOS device(snapback)

MBU Multiple Bit Upset Several memory bits upset bypassage of the same particle

SEFI Single Event FunctionalInterrupt

Corruption of control path by anupset



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Single event effects• Contributing particles

Heavy ions: (dE/dx)i z2Z/mv2

Protons through nuclear spallationreactions

• Classification of SEE Transient effects

Change of state which is non-distructive and recoverable(e.g., Single Event Upset)

Potentially catastrophic events May cause destruction unless corrected in a short time after they occur

(e.g., Single Event Latch-up) Single event hard errors (SHE)

Catastrophic failure of a single internal transistor in a complex circuit Single event functional interrup (SEFI)

SEU in control circuitry places the device into an unexpected state

E.g., Si(n,)Mg, Si(n,p)Al, Si(p,2p)Al



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• SEE environment characterised by Linear Energy Transfer Energy deposited in ionization per unit path length: (dE/dx)i

Integral LET spectrum Flux of particles depositing more than a certain amount of energy per unit

path length

• Devices characterised by Cross section

Effective area presented to the particles for a SEE to occur Function of LET

Critical charge Qc

Minimum charge to cause a SEE

Can be converted to critical energy (deposition) Ec

(in Si creation of an e-h pair requires 3.6 eV energy)

Critical charge for state changefor a number of Si technologies:

QC = (0.023 pC/m2)L2



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• LET spectrum ”Heinrich curve” combines all ions into one curve Gives the total number of particles with a given LET Ion fluxes folded by their respective energy loss curves

Fluxes of Ions F(Z,E)

LET spectrum f(L)



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Single event effects• SEU rate estimation for heavy ions (direct ionization)

Rate depends on ionization efficiency of a particle (i.e., (dE/dx)i = LET) and geometry of the interaction

Assume a regular parallelepiped geometry Exact path length distribution p(l) known p(l) = probability that a ray from an

isotropically distributed flux will followa particular length l

On path l, the energy deposited is l x dE/dx If the combination of various l’s in the

distribution and the various dE/dx’s (=L’s)

in the environment give energies > Ec, an upset will occur

max

/

max

max/)()(4/

L

lEc

l

LEcdldLLflpSU

S = total surface area of sensitive volume



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• Proton-induced SEU Produced by nuclear interaction Total up-set cross section as a funtion of proton energy experimentally Integrate the product of cross section and differential proton spectrum

Cross section can be fitted, e.g., by the two-parameter Bendel function

• Tools for SEU calculation CREME-96 main tool Implemented in Spenvis



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• Examples of Single Event Upsets

Barth & LaBel, LWS CDAW, 2002

SeaStar SEU rates



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Single Event Upsets

SOHO Solid State RecorderSEUs due to solar events

SOHO/ERNE proton fluxes at 110-140 MeV



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Sensor background and interference

• Particle-induced background Increased background due to charged particles and bremsstrahlung Increased signal processing requirements

reducing sensitivity increasing deadtime increasing signal processing complexity

Cerenkov and fluorescence radiation in optical sensors Photocathode noise in photomultiplier tubes Noise in microchannel plate detector Spurious signals Direct energy deposit in solid state detectors mimicking the expected

signal CCDs other Si detctors photomultipliers HgCdTe IR sensors etc.



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• Effects can be due to secondary radiation Secondary electrons (delta rays) produced by ions and electrons Induced radioactivity Neutrons produced by ions Bremsstrahlung produced by electrons Electrons produced by bremsstrahlung

• Direct thermal input to low-temperature systems up to 5 Wm-2 input passive radiators designed to operate below 100 K

• Precipitation of low-energy protons and relativistic electrons from the ring current to the atmosphere subauroral red arc interfering with optical systems at low altitudes



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Courtesy Marc SauvageCourtesy Marc SauvageCourtesy Marc Sauvage

“normal” “rev. 722”

ISO Camera Effects 97/11/06ISO Camera Effects 97/11/06

Solar proton event Nov. 97



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ESTEC TOS/EMA

Hipparcos star-mapper count rate from Dec 1989 till Feb 1993•penetrating electrons and protons•dynamic radiation belts•fluorescence and Cherenkov flashes in optical materials•direct signals photomultiplier tubes



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• Particles hitting CCDs charge up the pixels producing images similar to a star.

• The SOHO star tracker tracks five stars in small tracking windows. If a particle hits the tracking window it can result in a wrong assessment of the tracked star's barycenter. The SSU interprets this as a movement of the star providing wrong information to the

attitude control software.



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SOHO/ERNE particle fluxes andSOHO/LASCO, SOHO/EIT and SOHO/CDS images April 15, 2001



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SOHO/LASCO and SOHO/EITimages July 14, 2000

SOHO/ERNE proton intensities July 2000



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Less than 1 hour afterthe initial proton arrivalthe POLAR/VIS imageris saturated and remainsso for almost a day



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General conclusions

• Space weather does affect systems in space

• Pre-flight modelling of the environment pays back

• The response of the system to the environment must be well known and the design made accordingly to minimize the effects

• Sensitive science instruments need detailed simulations to evaluate, minimize, and remove the background

• Future systems likely to be more vulnerable More demanding performance requirements New technologies and sensor miniaturization Low power consumption Short mission development times and long mission durations

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 2004 Effects on Space...

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