E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 2004 Effects on Space Technology Space weather Michael J. Golightly NASA Johnson Space Center

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects Lanzerotti, 2001 ESTEC, Space Environments and Effects Analysis Section

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects Ground effects Effects on oil drilling Effects on train light signals (two documented events in Sweden)

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects 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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects Global effects

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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. Overview of space weather effects

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects 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 tumbling since the satellites in most cases are non-symmetrical Hubble Space Telescope drops 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.

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects Effects on man in space

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Overview of space weather effects Effects on technologies in space  Surface charging  Internal charging  Total ionising dose  Displacement damage  Single event effects  Interference and background in instruments SourceDrain Floating Gate ONO Tunnel Oxide Control Gate V CC Data Path Ionizing Radiation

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Plasma effects Surface charging Plasma effects on instruments

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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  -T e in eclipse ( and T e > 1 keV ) plasma } photoelecrons secondary electrons backscattered electrons artificial source I e +I i +I pe +I sec +I back +I art =0

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 the midnight-morning sector.

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 surface materials 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, electrons all surfaces  differential charging  worsens the otherwise favourable environment of high-density low-energy plasma

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

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

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Radiation effects Internal charging Total ionizing dose Displacement damage Single event effects Sensor background and interference

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Internal charging 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)

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Internal charging Time-integrated flux (=fluence) important  Charge builds up when charge leakage rate < charge collection rate  Discharge occurs when electric field > 2x10 5 V/cm  >2 MeV electron flux >3x10 8 cm -2 sr -1 d -1 for 3 consequtive days or >10 9 cm- 2 sr -1 d -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)

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 J/  > dielectric strength  discharge High-density of (lower-energy) electrons (LEO)  large J High-energy (lower-density) electrons (GEO)  high V }  High E

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Internal charging Potential targets for internal charging  Dielectrics  cable wrap  wire insulation  PCBs  feed-throughs  Floating conductors  PCB metallization islands CRRES results established the importance of internal charging as a source of anomalies Violet & Frederickson, IEEE Trans. Nucl. Sci. 40, 1512 (1993)

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

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

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 7.6x10 12 e-h pairs/rad(SiO 2 )cm 3

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 specification Radiation environment model } compute charged-particle fluxes f(E)  Radiation transport results D(E,d) Define simple shielding geometry calculate dose-depth curve D(d)=Σ E f(E)·D(E,d)  E }  Define actual geometry and shielding materials  Dose at a point E.g., Shieldose

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Total ionizing dose Spenvis/Shieldose-2 calculation of annual dose Examples of total dose-depth curves in various orbits Annual dose behind 4 mm spherical shielding on circular equatorial orbits (ECSS-E-10-04A).

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Total ionizing dose Total ionising dose effects  Caused by trapping of charge in insulators  bulk (SiO 2 )  recombination centres  field effects  interfaces (Si-SiO 2 )  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

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 N 10 (E) to derive the non-ionizing dose or the 10 MeV equivalent proton damage fluence Displacement damage is a cumulative, long-term mechanism ECSS-E-10-04A

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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=qn i /  g,  g =generation lifetime

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Displacement damage An example: SOHO solar array degradation and SOHO/ERNE Si detector leakage current SOHO/LASCO and SOHO/EIT images SOHO/ERNE HED Bias 3 Jan 96-Feb 02

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Displacement damage Joe H. Allen, SCOSTEP 2000/10/23

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects Contributing particles  Heavy ions: (dE/dx) i  z 2 Z/mv 2  Protons through nuclear spallation reactions 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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects 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 Q c  Minimum charge to cause a SEE  Can be converted to critical energy (deposition) E c (in Si creation of an e-h pair requires 3.6 eV energy) Critical charge for state change for a number of Si technologies: Q C = (0.023 pC/  m 2 )L 2

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects 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)

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring 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 follow a 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 > E c, an upset will occur S = total surface area of sensitive volume

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects 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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single event effects Examples of Single Event Upsets Barth & LaBel, LWS CDAW, 2002 SeaStar SEU rates

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Single Event Upsets SOHO Solid State Recorder SEUs due to solar events SOHO/ERNE proton fluxes at MeV

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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference 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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference ISO Camera Effects 97/11/06 Solar proton event Nov. 97

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference 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

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference 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.

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference SOHO/ERNE particle fluxes and SOHO/LASCO, SOHO/EIT and SOHO/CDS images April 15, 2001

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Sensor background and interference SOHO/LASCO and SOHO/EIT images July 14, 2000 SOHO/ERNE proton intensities July 2000

E. Valtonen, Space Research Lab. April 5, 2004 Seminar in Space Physics Spring Less than 1 hour after the initial proton arrival the POLAR/VIS imager is saturated and remains so for almost a day

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