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Exploring the MEO Space Particle Regime

Exploring the MEO Space Particle Regime. Briefing to the National Space Weather Program Assessment Team 6 Jan 2006. Gregory Ginet AFRL/VSBX Space Vehicles Directorate Air Force Research Laboratory. Exploring MEO Why Bother?.

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Exploring the MEO Space Particle Regime

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  1. Exploring the MEO Space Particle Regime Briefing to the National Space Weather Program Assessment Team 6 Jan 2006 Gregory Ginet AFRL/VSBX Space Vehicles Directorate Air Force Research Laboratory

  2. Exploring MEOWhy Bother? • MEO is a desirable orbit regime when trading off number of satellites, global coverage and ground resolution • MEO comprises a dynamic space radiation and plasma environment • The MEO space environment is poorly quantified Electrons >~ 1 MeV Protons >~ 25 MeV

  3. Exploring MEOCurrent Standard Models (AE8 & AP8) Example: Medium-Earth Orbit (MEO) Example: Highly Elliptic Orbit (HEO) Model Dose rates behind 0.23’’ Al (>2.5 MeV e ; >135 MeV p) DOSE (Rads/s) J. Fennell, SEEWG 2003 L (RE) • For MEO orbit (L=2.2), #years to reach 100 kRad: • Quiet conditions (NASA AP8, AE8) : 88 yrs • Active conditions (CRRES active) : 1.1 yrs • AE8 & AP8 under estimate the dose for 0.23’’ shielding HEO dose measurements show that current radiation models (AE8 & AP8) over estimate the dose for thinner shielding

  4. Exploring MEOMEO from LEO? (electrons) Dosimeter data > 1.5 MeV electrons MEO (10000 km, 45 deg) HEO (Molnya) Qualitative signatures LEO (400 x 1600 km, 69 deg)

  5. Exploring MEOMEO from LEO? (protons) Dosimeter data > 25 MeV protons MEO (10000 km, 45 deg) HEO (Molnya) No signatures! LEO (400 x 1600 km, 69 deg)

  6. Exploring MEODemonstration & Science Experiment (DSX) • Wave-particle Interactions (WPIx) • 50-m tip-to-tip antenna boom • VLF receiver & transmitter • Loss cone electron detector & magnetometer • Low-Energy Imaging Particle Spectrometer (LIPS) • High-Energy Imaging Particle Spectometer (HIPS) 25-m Physical Sciences, Inc. 6-m 6000-km x 12000-km, 28 deg MEO orbit • High Energy Proton Spectrometer (HEPS) 25-m • Space Weather Sensors (SWx) • Data for models in critical orbit regime • Determine near-field antenna environment • Compact Environmental Anomaly Sensor (CEASE) • Space Environment Testbed (NASA, AFRL) • Measure space environmental effects on materials and electronics • Determine component system performance • Low Energy Electrostatic Analyzer (LEESA) Designed for stand alone or EELV ESPA options Amptek, Inc. SWx and WPIx payloads on DSX will determine MEO wave and particle distributions – critical for development of climatology, nowcast and forecast models - rated #2/44 in 2005 DoD SERB!

  7. 105 104 rads(Si)/yr Quiet 103 102 Quiet DSX Orbit 1 (6000 x 12000 km, 28 deg) 101 DSX Orbit 5 (6000 x 12000, 63 deg) X 10 X 30-80 106 105 Active rads(Si)/yr 104 Active 103 102 From CRRESRAD model

  8. DSXSWX Sensors HIPS HEPS LIPS CEASE LEESA Sensors HIPS CEASE LCI LIPS LEESA

  9. Exploring MEOWave-Particle Interactions ELF/VLF Waves Control Particle Lifetimes L shell = distance/RE Particles mirroring below 100 km are “lost” Electromagnetic wave Pitch-angle Electromagnetic waves in the Very Low Frequency (VLF) range (3-30 kHz) scatter and accelerate radiation belt electrons through cyclotron resonance interactions

  10. DSXWPIx Motivation Particle lifetime along field lines (approximate 1D solution) Diffusion coefficient along field lines Wave power in the magnetosphere Diffusion coefficients along field lines Full 3D global, time dependent particle distributions Xi = (L, E,  ) Distribution of Resonant Wave Vectors An understanding of VLF wave power distribution & resultant wave-particle interactions is crucial for radiation belt specification & forecasting Wave-particle resonance condition Complex dependence on energy, frequency, and pitch angle Diffusion coefficients = sum over resonances

  11. DSXWPIx Payload • Receiver: • Three search coil magnetometers • Two dipole antennas • Frequency range: 1 – 50 kHz • Transmitter: • 1 – 50 kHz at up to 1 kW • 50 kHz – 750 kHz at 1W (local electron density) • Loss Cone Detector • Pointed into the loss cone, measures 100-500 keV electrons • Correlates loss cone filling with natural and/or transmitter generated events • DC Vector Magnetometer • 0-8 Hz three-axis measurement

  12. Exploring MEOSummary • MEO is a desirable orbit regime but poorly quantified • DSX science goals: • Improve understanding of dynamical processes in the slot region • Develop radiation belt specification and forecast models for the MEO region • Improve understanding of VLF propagation and wave-particle interactions • DSX technology goals • Provide improved climatology models to allow spacecraft manufacturers to optimize designs • Provide data to DSX SET experiments to help evaluate radiation effects on those systems. • Validate VLF wave injection models from space and ground based platforms

  13. Back-up Slides

  14. Space Weather in MEOA Dynamic Environment Solar cycle Geomagnetic storm and proton event Solar x-rays Solar protons Solar wind velocity Electrons Protons Solar wind magnetic field 7.0 7.0 L shell (Re) L shell (Re) Geomagnetic Activity Index 1.0 1.0 18 months 18 months Dynamic radiation belts

  15. Model differences depend on energy

  16. Space Weather in MEODSX Coverage Pitch-angle resolution enables mapping of distributions above orbit track

  17. Wave-Particle InteractionsExperiment Concept of Operation ~ 1 sec VLF sounding to determine far-field properties Volts/m ~ 100 msec Transmitter Signal Time Volts/m Receiver Signal Time ~ 2 sec Volts/m Transmitter Signal Time Counts/sec Stimulated particle precipitation to determine wave-particle interactions Loss Cone Particle Detector Time

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